SOME OQSERVATIONS ON THE UFE NESTOR)!

AND 320mm as auccummxgmgusnm MURT.
m A mscmm woomor

Thesis 50'! 9M chm cf M. S.

MECHQGAN STATE UNIVERSETY

Charles Francis Gibbons
1960

 

OVERDUE FINES
per 1m

25¢ perd

RETURIING ”LIBRASX MATERIALS:
Place in book return to
charge fr one circuIAtion records

SOME OBSERVATIONS ON THE LIFE HISTORY AND BIOIDGY

OF BUCCULNTRIX AINSLIELLA HURT. IN A

 

MICHI GAN WOODIDT

by

CHARLES FRANCIS GIBBONS

Submitted to the College of Science and Arts
of Michigan State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Entomology

1960

 

Approved 1/ ,

r

I

ABSTPZCT

This study describes the biology and life history of Brcculatrix

 

ainsliella Murt. in Baker woodlot on the Michigan State University
campus in 1959. The insect was collected periodically in all stages
of its life history. Eggs and larvae were observed from leaf samples
collected in plot areas. Instars were determined in the larval stage
by the measurement of head capsules. Change in head structure and body
growth was noted in immature forms.

The size, number, aplearance and position of first and second

generation mines of E. ainsliella in the leaves are recorded. Cons-

 

truction, size, location and number of moulting tents were observed
on the host leaves. Habits of dispersal were observed for this insect
in the larval stage.

The description, location and<zonstruction of the cocoon of E.
ainsliella was observed and apyearance and emergence of the pupa was
discussed. The appearance and habits of adults are discuSsed on the
basis of observations from both generations. Experiments to determine
feeding habits of the insect on white oak, red oak and sugar maple were
carried out. Percentage overwintering and summer pupal mortality and
parasitism was obtained. Parasites of the insect were determined and

natural predation was observed in the field.

SOME OBSERVATIONS ON THE LIFE HISTORY AND BIOLOGY

OF BUCCULATRIX AINSLIELLA MURT. IN A

 

MICHIGAN WOODIDT

by

CHARLES FRANCIS GIBBONS

A THESIS

Submitted to the College of Science and Arts
of Michigan State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Entomology

1960

x}!

‘1‘».

ACKNOWLEDGEMENTS

The author wishes to express deep appreciation to Prof. Ray Hutson
and Dr. James W. Butcher for their guidance in the construction of this
thesis as well as making some financial arrangements for the project.
Their interest continually influenced and encouraged the writer towards'
completion of this investigation.

Acknowledgement is extended to Dean L. Haynes, graduate student in
the Department of Entomology, for his constructive criticism of the
tables and graphs, and to Dr. Philip Clark for his suggestions on
statistical treatment of the data.

The writer is also indebted to Miss Annette Braun, of Cincinnati,
Ohio, and P. I. Oman of the U. S. National Museum for making positive
identification of the species worked with in this thesis.

Finally thanks are extended Dr. John Cantlon, Department of
Botany and Plant Pathology, Dr. Victor Rudolph, Department of Forestry,
and Dr. Roland Fischer, Department of Entomology for serving on the

writer's committee and offering criticism of the material.

111

TABLE OF CONTENTS

Acknowledgements . .

Introduction . . . . . . . . .

Review of Literature . . . . . .

Description of Experimental Area .

Sampling and Collecting Procedure

Description and Life History

of Bucculatrix ainsliella

 

Baker WOodlot, 1959 . . . . . .

Egg

Stage . . . . . . . . .

Mining Stage . . . . . . . .

Emergence from Mines . .

Free Feeding Stage . . .

First Moulting Tents . .

Second Moulting Tents .

Cocoon Stage . . . . . . . .

Description of the Cocoon
Formation of the Cocoon
Description of the Pupa

PUpal Emergence . . . .

Adult Stage . . . . . . .

Host Preference and Range . . .

Factors Affecting Abundance . .

Control

Summary

Bibliography . . . . . . . . . .

iv

Page

 

iii

14

16

19

19

23

25

30

3O

33

35

35

36

37

37

38

42

46

50

51

53

LIST OF TABLES

Table ' ' Page

 

1 number of Eggs Found in Dissected Females of
Bucculatrix ainsliella, First and Second
@nerations o o o o o o o o o o o o o o o o o n o o o o o ‘ 24

 

2 Egg and Mining Stage of Bucculatrix ainsliella,
Second Generation . . . . . . . . . . . . . . . . . . . . 26

 

3 Mbulting Tents of Bucculatrix ainsliella: First
and Second Generations . . . . . . . . . . . . . . . . ., 34

 

4 Overwintering Pupal Mortality of Bucculatrix
ain811ella .. I O O O I O O I O O O O O I O I O O I I O I 40

 

 

Figure

II

III

IV

LIST OF FIGURES

Life History Chart of Bucculatrix ainsliella . .

 

First and Second Generation Mining and Free Feeding
Stages of Bucculatrix ainsliella . . . . . . . .

 

Frequency Distribution of Head Capsule Sizes Found
in Bucculatrix ainsliella, Second Generation . . . .

 

First and Second Adult Emergence and Mbrtality in
the PUpal Stage of Bucculatrix ainsliella . . . . . .

 

Rates of Increment Growth of Nerthern Red Oak and
American Beech in Baker Woodlot . . . . . . . . . .

vi

Page

20

-22

28

39

45

LIST OF PLATES
Plate Page

I Cocoon of E. ainsliella . . . . . . . . . . . . . . . . . . 56

 

II Adult of E. ainsliella. . . . . . . . . . . . . . . . . . . 56

 

III Eggs of g. ainsliella . . . . . . . . . . . . . . . . . . . 57

 

IV First moulting tent of E. ainsliella. . . . . . . . . . . . 57

 

V Second moulting tent of E. ainsliella . . . . . . . . . . . 58

 

VI Larva of g. ainsliella . . . . . . . . . . . . . . . . . . 58

 

vii

SOME OBSERVATIONS ON THE LIFE HISTORY AND BIOLOGY OF

BUCCULATRIX AINSLIELLA HURT. IN A MICHIGAN WOODLOT

INTRODUCTION

In both 1958 and 1959, leaves of northern red oak, Quercus rubra

 

DuRoi, growing in Baker Woodlot on the campus of Michigan State Univere
sity had been fed upon by a mining and skeletonizing insect,
Bucculatrix ainsliella Murtfeldt. The study reported here was under-
taken in order to supplement published notes on life history, biology,
and ecology of the species.

Although the adverse effect on the growth of the trees was not
conspicuous, it was thought that persisflnflzinfestations of mining and
skeletonizing conceivably could cause permanent injury to the trees and
perhaps eventually bring about changes in stand composition.

In 1958 and 1959, injury by B. ainsliella was noted in Ingham,

 

Allegan and Kent Counties in Michigan. The possible influence of en-
vironmental conditions and natural enemies in terminating the outbreak
before host injury can manifest itself was considered in planning the
work reported here.

Because of the high populations present, data were easily obtain-
able in all stages of the insect's life history once the observer knew
‘what to look for. Due to unfamiliarity with the species, however, it
was not possible to obtain good first generation observations in 1959.
Furthermore, DDT'was sprayed by airplane early in the spring of 1959

in the vicinity of the woodlot. Subsequent observations indicated
1

2
that the spraying did affect the adult stage of the overwintering popu-
lation, since only two adults were found after spraying, whereas before
treatment they were numerous. Eggs apparently had been laid before
spraying took place, so that the overall effect on the population was

not serious as far as this study is concerned.

REVIEW OF LITERATURE

The earliest biological reference to the genus Bucculatrix ac-

 

cording to Needham st 21. (1928), is found in the first volume of

de Geer's "Memoires" published in 1752 entitled "Memoires pour servir
a l'historie des insects,? in which is given the life history of a
"little caterpillar with sixteen legs; smooth, green, which feeds on
the lower side of the leaves of Frangula." It was the manner in which
this insect spun its cocoon which attracted the attention of de Geer.

A description of cocoon construction, the pupa, larva and injury to the

host plant are given. The species described was Bucculatrix frangubella

 

Goeze and the host plant Rhamnus frangula, Buckhorn.

 

The larvae of several species of Bucculatrix are known in Europe;

 

but in this country, until Clemens' (1872) mention of B. pomifoliella

 

C1em., there had been no known publications.

The genus Bucculatrix was placed in the family Lyonetiidae by

 

Zeller in 1748, according to Stainton (1867). The genus included a
group of minute leaf-mining moths, the adult antennae of which possessed

eye caps. Stainton (1867) in the first general treatise on Bucculatrix,

 

placed the genus in the Tineidae. Up until 1873 this genus was usually

associated with Lithocolletis and allied genera, but according to

 

Friend (1927), the fact that it is an external feeder, (except for a
very brief period), the absence of palpi and tongue; eye cap, and the

different neuration of the wings appear to constitute generic differences.

4

Bucculatrix is usually classified today in the Lyonetiidae and is

 

so classified by Forbes (1923). There are, of course, differences of
opinion as to the classification of Lepidoptera and of this genus in

particular. Forbes places Bucculatrix in the family Lyonetiidae of the

 

super-family Tineoidea, but Mosher (1916) places it in the family
Bucculatrigidae of the super—family Gracilarioidea, basing her decision
on pupal characters. Fracker (1915) places the family Bucculatrigidae
in super-family Tineoidea as classified by larval characters. The
grouping of families and genera in the Tineina is still apparently open
to question. The genus will here be placed in the family Lyonetiidae
according to Forbes (1923).

The family Lyonetiidae, as usually defined, according to Craighead
(1950), includes numerous species of tiny moths which have structural
characters in common, but having larvae whose habits and forms differ
considerably. The majority of the species of Lyonetiidae, however, fall

within the genus, Bucculatrix; the "ribbed-cocoon makers." The adults

 

of Bucculatrix as described by Craighead (1950) have the vertex of the

 

head smooth, and the basal segments of the antennae extended to form an
eye cap fringed with stiff hairs. The wings are lanceolate, the hind
pair broadly fringed with scales and usually with brown, black or sil-
very white markings.

Needham £5 21. (1928) divide the family Lyonetiidae into three
groups: I - Lyonetia group, whose tissue feeding larvae are miners
throughout life but pupate outside the mine; 11 - Phyllocnistis group,
whose larvae form a chamber at the end of the mine in which they pupate;

and III -- the Bucculatrix group, whose ordinary tissue-feeding larvae

5
are equipped with strong thoracic legs and which mine in the first lar-
val stage only, feeding thereafter openly on the leaf surface.

The original description of Bucculatrix ainsliella is as follows

 

according to the description by Murtfeldt (1905):

"Antennae about three fifths the length of the fore
wings, annulated in dusky brown and dull yellow. Eye caps
golden white, expanded. Apical tuft long, projecting for-
ward, dark brown in centre, shading outwardly to dingy
white. Face satiny cream-white. Thorax cream white, more
or less dusky, overlaid with dark brown scales, with small
but distinct dark brown spot on center of dorsum, two
rather narrow marks of same colour forming a triangle or
open V on posterior joint, back of which is a silvery
white band. Forewings: ground colour, shining cream white,
more or less obscured by dark brown scales which in some
lights exhibit purplish reflections. The pattern, which,
though less deeply shaded in some specimens, than in others,
is quite unvarying, consists of a dark brown longitudinal
band from the base along the costa, gradually broading to
the apical third where it narrows and curves backward, leav-
ing the anterior margin to the apex merely speckled with the
dark scales. The inner margin to beyond the Middle is but
sparsely irrorate with brown, but has just below the cell,

a conspicuous purple brown spot curved on its upper edge,
but straight on the margin of the wings, so that when the
wings are closed it presents the appearance of a broad oval
patch, one half of which is on one wing'and the other half
on the other. Fringes corresponding in colour and suffuse
with the body of the wing. Hind wings pale silvery gray,
the fringes tinged with brown. Abdomen irridescent gray,
terminating in pale brown tuft. Tibiae of posterior legs
clothed with long, buff-coloured hairs.

”Alar expanse from 7 to 8 mm. The pupae are sooty
black and before the moths issue are protruded about two-
thirds of their lengths from the cocoon." This insect
was named after Mr. Charles N. Ainslie of Rochester,
Minnesota.
Identification of the specimens worked with in this paper were

confirmed by A. Braun.

Bucculatrix spp. has a wide variety of host preferences but most

 

of these appear to be annuals. Below is a general review of some of

the more important species in the genus Bucculatrix.

 

Bucculatrix canadensisella Chambers

 

The birch skeletonizer according to Friend (1927) occurs from the
southeastern United States into Canada. It extends,down the Allegheny
mountains to North Carolina and has been known to occur as far north as
the Yukon River in Alaska. Its food preference includes the following

birch species: Betula populifolia Marsh, §.papyrifera Marsh, B. lutea

 

 

Michx., and.§,l§222 L. According to Lamburt (1943), several regions of
especially thick stands of white and yellow birch in the St. Jehn's
area, Quebec, were infested in 1949; the trees exhibiting an autumnal
appearance.

Friend (1927) found that heavy outbreaks at more or less regular
intervals are a common phenomena with this insect. There is but one

generation a year of B; canadensisella, the adults emerging around June

 

or July. The mining period averages between 24 and 31 days; two in-
stars occurring while mining and three while free-feeding, the latter,
lasting from 13 to 15 days. According to Friend (1927), the cocoon is
spun on the ground under debris. The last larvae are found in the lat-
'ter part of September. This larva spins silk threads while emerging
:from the mine. It does not feed between the time of emerging and forma-
‘tion of its first instar tent. Hutchings (1925) states that the pri-
Inary periods of infestation come at the end of the summer when the
:foliage is beginning to fade. Consequently the insect is not readily

detectable.

Epcculatrix albertiella Busck
The oak ribbed-case moth has infested oaks on the west coast ac-

cording to Essig (1926). The pupal stage as described by him is an

elongated, pure white ribbed cocoon surrounded by a palisade of fine
silken hairs. The larva hatches and mines immediately, later forming
the typical moulting tents and cocoon. In some areas it is fairly
common and does not do much damage. Occasionally in a heavy infesta-
tion such as occurred around Vesabia, California, in 1952, it can do
considerable harm. Brown (1953) states that the adults apparently ap-
pear in May and'June. Essig (1926) states that the wing expanse of

this insect is about 8 mm.

Bucculatrix pomifoliella Clemens

 

The ribbed—cocoon-maker of apple infests trees of the genus Mglus
and is fairly common throughout most of the United States according to
Snodgrass (1922). This insect characteristically mines and free-feeds
on apple leaves in much the same way as other members of the genus.
Damage is easily detected by the presence of a dark, purplish-red dis-
coloration of the leaf immediately around the larva. Snodgrass (1922)
states that this insect does not moult in the mine but, like B.

ainsliella, appears to have three instars in the free-feeding stage.

 

This insect has two generations a year; the adults being present both
in May and midsummer. Just before the cocoon is formed, according to
Snodgrass, 1922, the insect forms a stockade of silk palisades which
surround the cocoon as if to serve as a protective measure. The cocoon
formed by the insect has peculiar valve—like partitions on the inner
pupal chamber, making the space inside very small; three chambers in a
row are formed at the anterior end of the case. Larval coloration ac-

cording to Snodgrass (1922) is characteristically pale yellow.

Bucculatrix ulmella Zell.

 

Literature on the elm ribbed cocoon maker is concerned with in-
festations in the vicinity of New York. According to Felt (1921) who
described the insect, the larvae mine irregular areas on the underside
of elm leaves. The larval tents formed are about 2 - 2.5 mm. and are
found scattered upon the foliage. The larvae are pale grayish green,
head light brown, the thoracic shield a pale yellow. The insect con-
structs the typical cocoons but differs from the apple and birch spe-
cies by being greyish black. Felt (1921) thinks this to be an intro-

duced species.

Bucculatrix needhami Braun

 

This insect is one of a group of closely related stem-boring in-
sects which form galls, and according to Braun (1956), is characterized
by the same general type of genitalia and wing markings. This species

is found in Florida, forming galls in Heliconthis agrestis Pollard, a

 

sunflower. The walls of the insect galls vary in size and usually oc-
cur singly on the stem; if there is more than one, they are imperfectly
formed. Length of full grown larvae varies from 10 - 12 mm. and over-
winters in this stage, having two instars within the gall. Needham
(1948) states that in mid-spring, hypermetamorphosis occurs in this in-
sect. The larva in this stage gnaws through the wall to the outside.
Here it moults again, the body appearing to shrink. According to
Needham (1948), the duration of this stage is about a week. It then
forms a typical cocoon, selecting the most exposed places available.

The adultiis about 6 mm. in length. Needham, in rearing out this

9
insect, had much difficulty with ants, mites, and Mordellid beetle lar-
vae which killed many of his specimens. These, he concludes, probably

account for some natural predation as well.

Bucculatrix fusicola Braun

 

This insect produces a spindle gall on the sunflower, Helianthus

 

trachelifolius Mill. and according to Breland gt 21. (1948) its habits

 

are very similar to B. needhami. The galls are 1.5 mm. by 1 cm. in
size and are formed from late July into August. Most of the larvae of
the gall maker became mature in the fall, attaining a length of 7 - 9
mm. and become a light cream color. No pupae were found by Breland

gt 21. (1948) until spring, when just prior to pupation they attained
a greenish gray color; the skin becoming loose and wrinkled. After
gnawing a hole in the side of the gall, the larva emerges and spins its
cocoon on the stem of the plant near the gall. Cocoons are about 1 cm.
long and always formed with the head directed away from the gall.
Breland st 21. (1948) estimates that 42 percent parasitism occurs.

These parasites included Eupelmus cyaniceps Ashm., Eurytoma sp. and

 

a new species of Microbracon, family Braconidae. Eupelmus cyaniceps

 

 

Ashm. is most often an external parasite.

Bucculatrix althaeae Busck

 

According to Busck (1919) the hollyhock leaf skeletonizer has been
found infesting hollyhock Althea L. sp. in California. But since hol-
lyhock is an introduced plant, the insect apparently has other native
host preferences. Busck (1919) describes the insect as having a black

head and a gray thoracic shield with numerous (20) small black dots.

10
The body is gray with darker bands across each joint. The cocoon is

about 5 mm. long, with a yellowish tint.

_Buccu1atrix ambrosiaefoliella Chambers

 

Chambers (1882) describes this insect as a feeder on the leaves

of Ambrosia trifida L. It is quite common in Kentucky. After emerg-

 

ing from the egg, it feeds from three to four days, being a dull white
color. It then doubles itself up and undergoes its first moult in the
mine. The second instar appears striped longitudinally with a dorsal
green stripe margined on each side by a white line; beneath which is
another green stripe on each side. It remains in the mine and feeds
for about one day after its first moult; then leaves and feeds extern-
ally for about two days on the underside of the leaf. According to
Chambers (1882) one instar tent was formed and about three days later
a cocoon was observed. This gives the mining and free-feeding stage
comparatively little time to develop. From the author's experience

with other members of the genus Bucculatrix and in particular

 

ainsliella, the validity of the time intervals stated by Chambers

 

(1882) is doubted.

Bucculatrix cunegira Meyrick

 

Braun (1920) gives one of the host plants of this insect as aster,

Aster shortii Lind1.6.n Bmthen and Hooker, 1893 ). Miners make character-

 

istically transparent, long, linear, compacted mines in the leaves in
autumn. In early November, in a slight enlargement at the end of the
mine, the larva spins a flat, yellow, circular, wintering cocoon;

(similar in appearance to the moulting cocoon, but of denser texture)

11
within which it lies curled during the winter. In March of the fol-
lowing year it leaves this "cocoon" by a circular opening, and bores
into a growing shoot just below the tip, hollowing out the stem and
killing the shoot. It feeds downward for about an inch and eats its
way out. It then forms the typical pupal cocoon on the surrounding
vegetation. The larva is yellowish white with two black spots on the
dorsum of the first thoracic segment. The head is eyllow. Braun

(1920) estimated that about one percent complete their life cycle.

Bucculatrix thurberiella Busck

 

The cotton leaf perforator, according to Folsom (1932) mines the
leaves of wild and domesticated cotton, Thurberia sp. The larvae mine
and later free-feed on the leaves, giving the foliage a lacelike ap-
pearance. Characteristic of the larvae are the black eyespots, prom-
inent white tubercles, and particularly a pair of round, black spots
at the border of each body segment. Folsom (1932) describes the egg
as pale yellow with longitudinal ridges. It stands on one end on the
leaf surface. Generations of this insect last from about 15 to 70
days, depending on the season. A generation averages 18 days and

Folsom (1932) states that there may be 9 to 10 generations annually.

Bucculatrix gossypiella Morrill

 

This species is mentioned because according to Morrill (1927), it

was once confused with B. thurberiella Busck, owing to the similarities

 

of coloration, host plant, and locality. The egg appears greenish to
z
transparent. The larval head is brownish; the pronotal shield green-

ish yellow with a small black spot transversely broadened near the

12
posterior margin. The body is dull yellowish green. The adult wing

expanse is from 5 to 8 mm.

Bucculatrix fugitans Brown

 

An important host species as stated by Braun (1930), is hazel,

Corylus americana L., in which the larvae form linear mines and later

 

free-feed on the leaf surface. The larvae resemble the leaves, turn-
ing from a yellowish to a pale green in the second instar. The cocoon
construction described by Braun (1930) is typical but reddish brown,

short and stout.

Bucculatrix chrysathamni Braun

 

This insect is mentioned bebause of the peculiar habit noticed by
Braun (1925), that the adult has of resting at the extreme tip of the
linear leaves of rabbit bush, with its head projecting beyond the apex

of the leaf.

In the above described habits and preferences of some members of

the genus Bucculatrix, it can be seen that although their general life

 

history is similar, they do vary considerably. The body structure in

some species varies as in B. althea and B. gossypiella, which possess

 

a thoracic shield. Color also varies considerably but whether this
may serve any protective advantage or not is debatable. ‘B. ulmella
and B. fusicola deviate from the usual yellow coloration but its
habitat remains the same. Probably the largest variation between
their life histories is their number of instars and instar tents.

B. ambrosiaefoliella and B. needhami form only one moulting tent and

 

13
vary in the length of free-feeding time. B. needhami overwinters in
the larval stage in the stems of sunflowers. B. fusicola also does
this but its range is farther south.

Biological characteristics of the adults are not mentioned in

the literature with the exception of B. chrysathamni.

 

DESCRIPTION OF EXPERIMENTAL AREA
Baker woodlot, located on the University campus is typed ecologi—

cally as Beech - Sugar Maple. American beech, Fagus grandifolia Ehrh.

 

and sugar maple, Acer saccharum Marsh, are dominant in both overstory

 

and undergrowth. Red maple, Acer rubrum L., white ash, Fraxinus ameri—

 

 

cana L., and northern red oak, Quercus rubra DuRoi, are common over

 

large areas of the woodlot. The latter two species are found in the
more open areas. Trees are uniformly spaced, and the canopy is con-
tinuous except where windfall has destroyed some of the dominants. A
lack of certain size classes exists in some tree species, eg. white

ash, hornbeam, Carpinus caroliana Walt., and red oak; due to cuttings

 

20 years ago. Litter cover is substantial, remaining heavy during
most of the growing season.

The study area is well drained, containing loamy sand with slight
erosion. Natural reproduction of all species mentioned was found,

with the exception of basswood, Tilia americana L.

 

Description of Experimental Plot

 

With the exception of samples taken of overwintering pupae, all
sampling was done in plot areas of uniform size. Data were obtained
from dominant red oak, located on the west end of the woodlot. The
trees were found in sufficient numbers along with a mixture of dominant

white oak, Quercus alba L., and red maple. .The understory consisted of

 

14

15

red oak, spicebush, Lindera benzoig L., witchazel, Hamamelia virginiana

 

 

L., and red maple.

SAMPLING AND COLLECTING PROCEDURE

Overwintering Pupae

 

Pupae were collected during March and April to determine percent
adult emergence and pupal mortality, respectively. Four plots were
set up at random in the woodlot as follows: a northern red oak was se-
lected as a center point and a 100 foot diameter circular area was
paced off around it. Beech, red oak and maple were selected as samp-
ling trees. One hundred pupae from each species of tree were collected
with forceps and placed in glass vials. From these four plots, 12
vials of 100 pupae each were collected, taken to the laboratory and
placed in labled 1 quart cardboard ice cream containers to await emer-
gence. Pupae from each tree species in each plot were kept separate.
Parasites that emerged in advance of moth emergence were removed when
found. The moths were allowed to remain in the containers one week
after first emergence. Both emerged adults and pupae were then re-

moved in order to determine mortality in the pupal stage.

Bdults

 

Adults found on the red oak, beech, sugar and red maple were col-
lected periodically in glass vials until such time as they could no
longer be found. Collections were made by placing vials immediately
beneath the insects, and then pushing the cover down on top of them.
Specimens were brought back to the laboratory to determine sex ratio

and egg counts. The moths were immobilized by passing carbon dioxide

16

17
over the glass vials, after which they were removed and placed in

watch glasses containing 70 percent alcohol.

Leaf Samples

 

Dominant northern red oaks were selected as leaf sample trees
within the plot area. These trees were marked with paint. From June
16 to October 16, two leaves from each of five trees were removed with
a tree pruner from a point between 15 and 30 feet above the ground
(about 1/3 to 1/2 the distance to the top of the tree crown). Samples
were selected on the basis of leaf size and infestation, and were made

every three days.

Eggs

Leaves were taken into the laboratory and examined under the mi-
croscope for eggs and injury. Eggs were recorded in three categories:
(1) those completely transparent (undeveloped); (2) those showing some

development (as indicated by a conspicuous dark head capsule); and (3)

those in the process of hatching.

Larvae and Description of Mines

 

The number of mines per unit area of leaf surface was recorded
and mine area measured with micrometer calipers. The first generation
mines were not recorded at the time of first generation feeding but
they were counted separately in late summer along with the second gen-
eration mines in order to compare populations of both generations.
First generation mines were determined by the appearance of dry leaf

tissue surrounding the infested areas on the leaves. Second generation

18
minings exhibited dark stainings on the lower leaf surfaces. Larvae
were collected at random throughout the plot area, without regard to
the tree species on which they were found. These were placed in glass
vials and brought back to the laboratory where they were immersed in
KAAD1 for five minutes. After immersion, they were removed, wiped dry,
and body and head capsule size were measured by micrometer calipers

and glass slide micrometer respectively. They were then preserved in

70 percent alcohol.

 

1KAAD is a standard preservative for insects. It contains 8 percent
kerosene, 68 percent absolute alcohol, 16 percent acetic acid, and
8 percent dioxane.

DESCRIPTION AND LIFE HISTORY OF BUCCULATRIX AINSLIELLA

 

IN BAKER WOODLOT - 1959

Both first and second generation egg, larvae, pupal and adult in-
cidence are recorded graphically in Figure 1. Information on first
generation development is incomplete because of unfamiliarity with the
appearance of the various stages. 0n the basis of incomplete first
generation and detailed second generation observations, it is possible
to construct a record of events for the spring, summer, and fall of

1959. A description of the important recognizable phenomena follows.

Egg Stage

In July 1959, within three days to a week after adult emergence,
eggs were found on the underside of red oak leaves. The eggs them-
selves were almost always laid on the underside of the leaf along
major veins in the angle formed by the vein and the leaf epidermis.
The egg had an oval appearance within the female but upon oviposition,
took the shape of the support on which it was deposited; flatly ovid
and about 0.25 mm. in diameter. It was invariably stuck to the under-
side of the leaf by an adhesive substance which completely covered
the egg. This material extended out on the leaf slightly, where the
periphery of the egg comes in contact with the leaf surface.

The egg surface had a hexagonal sculpturing, which the author did
not see within the female prior to oviposition. The eggs were almost

always laid singly; rarely three at a time, in a row. Adults of the
19

20

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21

overwintering generation oviposited primarily on the outer edges and
lobes of the leaves. Eggs of the second generation were more centrally
located on the leaves, extending down the main veins and sometimes even
to the base of the petiole.

‘The undeveloped egg is very pale and creamy to white in color.
Usually it is quite transparent. Because of this transparency,the two
thickened sides of the head capsule became visible within two days af-
ter oviposition as black spots within the egg. These gradually merged
to form a recognizable black head. The period from first black spot
formation to eclosion is designated in Figure I as the "Black head
stage." A short time before the larva leaves the egg, it can be seen
curled up inside the egg shell. In Figure II, the number of eggs in
the black head stage reaches a maximum about eight days after the first
eggs were found. There is a sharp decline in numbers almost immediately
as a result of hatching. In about three to six days, eclosion occurred,
and the young larva went directly into the lower leaf surface from the
egg. In Figure I, "hatching" is considered to be (in part)‘that period
when the insect has broken through the egg but part of the larva is
still in the shell. Shortly after the larva makes its way through the
leaf tissues, a brown stain occurs in the mine. If staining had not
taken place beyond the perimeter of the egg, hatching was considered to
be taking place. After hatching, the inside of the egg turns black be-
cause of the frass which is pushed back into the empty shell by the

young larva. This habit made it very easy to tell whether or not the

egg had hatched. In Figure II "Beginning Hatch" reached a peak about

war

22

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23
the same time actual “Mining" became abundant; on August 13th at 18
percent of its occurrence.

Table 1 depicts the average number of eggs carried by females in
both the overwintering and summer generation of the insect. It can be
seen that the summer generation of females averaged 89 eggs per indi-
vidual (Tahle lb) compared to an average of 66 eggs found in females
in the spring generation (Table la). If the limited data presented
here accurately reflect difference in fecundity for the two generations,
possibly the more rigorous conditions to which overwintering pupae were
exposed had an adverse effect on egg numbers.

It is not known if egg laying had occurred before the females were
collected and eggs counted. Eggs examined within the females showed
different stages of development and it may have been possible that the
females sampled produced eggs throughout their entire adult stage,

which therefore were still in the process of development.

Mining Stage

 

The mine of Bucculatrix ainsliella is a winding tubular gallery

 

which may give the appearance of serpentine mines of other genera. It
can be identified by the appearance of a splotched skeletonization
throughout the leaf (summer generation particularly). In Figure I this
is the "Mining Stage." It was observed that the young larva mines
close to the egg for several days but finally goes off in one direction.
While in the mine, the insects dorsal side was observed to be toward
the upper surface of the leaf. Although the brown stain on the in-

fested leaf appeared quite noticeable, only a small part of the

24

 

 

 

 

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.hnaoo was .H manna

25
.discolored tissue was injured by the miner. Evidently the mine sur-
rounds and isolates other leaf cells, resulting in their discoloration.
When the peak of the mining stage appeared, from 11 to 35 mines were
noticed on one leaf. The mining stage lasts from four to five weeks.

In Figure 11, the number of larvae in mines reached a peak on
August 17 in the second generation. The incidence of mine formation
appeared to be periodic, reaching peaks of 5, 14, and 8 percent of the
total on August 1, l7, and 31 respectively. It probably reflects the
timing of oviposition.

A chronological tabulation of (1) presence of new eggs; (2) par--
tially developed eggs (black head stage); (3) start of mining; and (4)
number of occupied mines for the second generation is shown in Table
2. This table is a supplement to Figures 1 and II; the latter particu-
larly.. The above four observations were recorded from leaf samples
and the percentages of the totals have been computed for the dates
shown. In Figure II, these results are designated as curves of abun-

dance and in Figure I, the lengths of the observations were recorded

as bar graphs along with other life history phenomena.

Emergence From Mines

 

The young caterpillars fed in mines for about ten days to three
weeks (Figure I and II), foraging along the smaller secondary veins
and occasionally crossing over these and some of the larger ones, fill-
ing tunnels with frass. In the work reported here, when the mining had

covered about one-sixth to one-third of a square inch of leaf area, the

Table 2. Egg and Mining Stage of Bucculatrix Ainsliella — Second

 

 

 

 

 

 

 

Generation.
Blackhead Starting Number
Date New Eggs Eggs of Mines Occ. Mines
No. % No. % No. % No. %

7/16 90 100.0
7/17 77 100.0
7/19 258 99.2 1 .4 l .4
7/22 204 89.1 21 9.2 4 1.7
7/25 95 53.4 64 36.0 19 10.7
7/27 105 27.1 158 40.8 124 32.0
7/29 73 17.7 27 6.5 44 34.9 169 40.9
8/1 28 4.6 24 3.9 260 33.7 300 49.0
8/3 8 2.1 192 49.5 188 48.5
8/6 111 23.3 158 ‘ 33.0 210 43.8
8/10 4 .7 282 49.2 287 50.1
8/13 4 .5 426 49.4 784 498.7
8/17 10 1.3 432 50.1
8/20 3 .5 626 99.5
3/24 ‘ 1 .3 361 99.7
8/27 321 100.0
8/31 456 100.0

9/3 ‘ 404 100.0

 

27
caterpillars left the mines through an elliptical slit near the end of
the tunnel on the lower leaf surface.

The whole process of emergence averaged one to two hours. The
larvae worked its head and thorax out until it obtained a good grip on
the leaf surface, after which it pulled itself out. In all the mines
examined, only one exuvium was found, suggesting that probably all
mining is done by one instar of the insect. It was very difficult to
determine the number of instars by examining the mines for head cap-
sules, because of the small size involved. With this in mind, two
dozen larvae were removed from the mines and figures on maximum width
of the head capsule recorded. According to Dyar (1890), the head cap-
sule is not subject to growth during any one instar and a constant
numerical ratio exists between the widths of the heads of any two suc-
cessive larval instars.

Figure III depicts the head capsule sizes that were determined
for second generation larvae. A micrometer was used to measure in
units of .01 mm. On the basis of frequency distribution, three peaks
occur between .08 mm. to .21 mm. The fact that only one head capsule
was found in all the mines examined, however, makes it difficult to
say that moulting takes place in the mines. The fact that a doubling
in head capsule width is embraced by the .08 and .16 measurements
suggests that at least one moult does take place in the mines, even
though it was not perceived by the writer. In previous descriptions

of the genus Bucculatrix, it had been stated or assumed that the min-

 

ing period included one instar only and that the first moult occurred

on the surface of the leaf. The only exceptions to this being Friend's

28

 

 

 

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29

(1927) description of B. canadensisella in which he found two instars

 

occurring while the insect was in the mining stage and Chambers (1882)

description of B. ambrosiaefoleilla, in which there appears to be a

 

clear cut difference between size of the second free feeding instar
and the third. Apparently the free feeding moulting takes place in

"tents" in B. ainsliella.

 

It is questionable whether the small number of measurements fall-
ing within the .28 - .30 size class can be considered to represent a
separate instar. The largest instar class appears to be in .14 mm.;
steadily decreasing as the instar size classes increase. Indirectly,
this may reflect differential mortality in the various instars. The
lack of well defined size categories in Figure 111 makes any estimate
of the number of instars extremely tentative. 0n the basis of the
measurements in Figure III, 3 or 4 instars might be surmised.

When first hatched, the larvae are minute, translucent and very
delicate. At first they appeared flattened, the head resembling some
larvae of Tineidae, which possess similar life habits and morphologi-
cal characteristics. By the time the larva left the mine, however, it
had acquired a typical caterpillar shaped body. The head which was
formerly prognathous had shifted to a hypognathous ‘position and
when fully grown, the larvae were about 5.0 - 6.0 mm. long. lost lar-
vae were medium to pale yellow; although some specimens were collected
that were yellow-green. After ecdysis, the mouth parts appeared well
developed and the five pair of ocelli on each side of the head were

more conspicuous.

30

Free Feeding Stage

 

First Moultinngents

 

In 1959 at Baker woodlot, the larvae upon emerging from their tun—
nels proceeded to feed upon the lower surfaces of red oak leaves, eat-
ing out the issues between the small veins. Within a week, they had
built special moulting tents in the general area of the eggs, next to
the larger veins. Sometimes a small depression on the leaf was se-
lected; a favorite spot being at the very tip where the edges curl up
slightly. Each larva laid down a thin layer of silk against the sur—
face; over which was woven a flat canopy, stuck fast all around the
edges, but having a hole in the center. The entire process of web for-
mation took about one to one and one-half hours. The caterpillar then
entered this "tent", closed the aperture with a webbing of silk spun
from the inside and proceeded to moult. The time spent in these tents
was about one and one-half to two days, (see Figure I "first moulting
tents occupied”). These tents were about 1.4 mm. in diameter in size.
Close observations showed that the caterpillar crawled into the tent
and assumed a position with its back towards the top of the leaf. By
bending and rubbing against the inner edges of the tent, the larval
skin became loosened. Since the diameter of the webs are not much
more than half the length of the larvae, the insects were forced into
a "U” shape. '

The web afforded the insect excellent protection. Its small size
caused the larva to be held tightly and its strong attachment to the

leaf secured the web against being washed, or lightly brushed off.

31
This web may also afford protection from predators; eg. ants and
Hymenopterous parasites.

Larvae removed from the tents appeared to moult normally. Inside
the "tents” much pulling was necessary to get rid of the old skin. A
few hours after moulting the larvae broke out of the webbing through
one side, at the point where the silk is attached to the leaf surface.
In moulting, the head capsule separated from the rest of the old skin
and was cast off first. The moulted head capsule and skin were left
inside the web. When larvae were removed from the web before moulting
was finished, they would spin another web or as much of another web
as possible and would then moult normally. Once removed from its web,
the insect always made a determined effort to form another one; al-
though moulting could take place outside.

The quiescent period is considered reached after the larva com-
pleted its webbing and formed a "U" shape. No change in shape or posi-
tion was noted when these were removed from the web in advance of
moulting.

In Bucculatrix canadensisella, Friend (1927) states that the

 

time spent in the first moult is related to temperature, and usually

 

varies between one and four days. B. ainsliella spent an average of
one and one half days in the first tents in Baker woodlot in 1959.

After emerging from the moulting tents ("first empty first moulting
tents found" Figure I), the larvae fed from three to six days. Newly
moulted larvae appeared slightly dehydrated and if left on a dry leaf
or surface for more than a few hours, shriveled up. The insect ap—

parently needs food immediately after moulting. During free feeding

32
periods, the insect wandered extensively over the leaves, migrating
from one to the other. Feeding took place on the lower side of the
leaves usually, but feeding on the dorsal side was not uncommon. Ex-

periments with B. canadensisella (Friend 1927) summarizes the effect of

 

upper leaf palatability or negative phototrophism on the insect's feed-
ing site preference. When host leaves were inverted, the insects wan—
dered to the lower surface showing an evident reaction to gravity and
a disregard for the difference in leaf surface. Although the lower
leaves were well illuminated, the insects exhibited no reaction to
light. The entire leaf surface was never consumed, nor were the small-
er cross-veins fed upon. Ordinarily the larva fed on an area for a
short time, and then moved around and fed elsewhere; sometimes even on
another leaf. The insect does not eat large areas of the leaves but
rather, many smaller parts, giving the leaves an overall appearance of
complete skeletonization.

If disturbed, the larvae usually dropped off the leaf or stem,
spinning a long thread as it fell. After falling a few inches, they
hung on the end of the thread a moment and quickly ascended. When the
larva stops its descent, according to Snodgrass (1922), it is attached
to the end of the thread by means of the spinneret. When it ascends
the thread, it moved its head rapidly back and forth and as observed
by Snodgrass (1922), wound the silk up on its prothoracic legs. Upon
reaching the leaf surface again it was observed by the author to drop

the silk.

33

Second Moulting Tents

 

As shown in Figure 1, within a week after first tent formation,
the insect forms a second moult tent. These are slightly larger than
the first; 2.5 mm. diameter in size; an increase of 1.1 mm. These may
be spun over any depression in the leaf, most of them being on the
lower leaf surface but occasionally on the upper surface as well. The
tent was formed in about an hour, and the insect took a position simi-
lar to that found inside the first moulting tent.

In Figure II, presence of both moulting tents can be seen as a
pictograph. Tables 3a and 3b contain the data from which the tent pic-
tographs in Figure II were drawn. Data on second instar tents are
more complete and consequently present a more accurate picture than do
the data for first moulting-tent occupancy. In Table 3b, where data
are good for both first and second moulting tents, a sudden decline in
the number of full tents is found after a short period. Within one
week, there is a drop in insects found in the first moulting tents of
62 percent as seen from September 14 to September 22. Likewise in the
second instar tents, on September 25, 90 percent were occupied;
whereas October 2 shows a sharp drop to 55 percent occupied tents.

All percentages cited are percentages of the total number of tents ob-
served for the season.

After emerging from the second moulting tent, the caterpillar re-
sumed feeding. It was during this period that most of the injury was
done to the leaves and large patches of skeletonizing were observed.

Throughout the free feeding stage, B. ainsliella was constantly on the

 

move, dropping from one leaf to another. Toward the last part of the

34

Table 3. Moulting Tents of Bucculatrix Ainsliella.

 

 

 

 

 

 

 

Date Total lst Moulting Total 2nd Moulting
Tents Tents Occupied Tents Tents Occupied
No. No. % No. No. %
3a. First Generation
6/17 114 26 22.8 119 81 68.1
6/25 72 3 4.2 29 11 37.9
6/29 66 0 0.0 52 10 19.2
6/30 199 O 0.0 74 11 14.9
7/2 158 0 0.0 117 - 11 9.4
7/8 165 1 .6 104 5 4.8
3b. Second Generation
9/8 4 0 0.0 0 0 0.0
9/11 64 55 85.9 7 4 57.1
9/14 194 125 64.4 4 3 75.0
9/18 208 127 61.1 0 0 0.0
9/22 132 19 14.4 5 3 60.0
9/25 161 58 37.0 26 19 73.1
9/28 135 16 11.8 74 15 20.0
10/2 54 0 0.0 103 19 18.4

35

free feeding period, a pair of bright yellow internal structures was
clearly visible through the dorsal integument of the fifth abdominal
segment of the larva. About a day before the larva pupated, it appar-
ently stopped feeding and traveled from the feeding area. When ready
to spin a_cocoon, the larva dropped from the leaf, spinning out a
thread up to 15 feet long as it went.h At this stage, caterpillars
that were feeding dropped very easily when the twigs were shaken, and
were wafted from one host to another; very often to plant species not
fed upon. Undoubtedly there is starvation when the insect lands too
far from its food source. This may be considerable when there are
strong rains or winds.‘

When the caterpillar was full grown it had reached a length of
about 5 mm. The body was thickest around the middle of the abdomen,
and the outer integument was naked except for small hairs distributed
over the body. The head was a dark yellow in the late free feeding
stages, with the body,a bright yellow or a greenish yellow. Pupation
occurred on tree trunks, contrasting with the earlier summer pupation
which took place on the trunks and leaves of all available vegetation.
Pupae were found on the ground in the fall but whether they can survive

the winter in such locations is questionable.

Cocoon Stage

 

Description of Cocoon

 

The walls of the cocoon consist of two layers: (1) a thick outer
layer in which lengthwise thickenings form rib-like structures; and

(2) a smoother inside lining which has a thinner texture. The outer

36
sheath is attached securely all around its base to a support, while
the inner layer forms a shelter chamber. Snodgrass (1922) noted simi-
lar appearance of the cocoon of Bucculatrix pomifoliella.

At the posterior end of the cocoon the last larval exuvium could
be found. This was shed about two days after the cocoon was completed

(summer generation).

Formation of Cocoon

 

When the larva was ready to pupate, a thin base of silk was laid
down. The base was formed of a multitude of irregular figure 8 loops
as the insect moved its head from side to side.

The tapering end of the cocoon is formed first, starting with a
small mass of silk which is worked backward by the insect as the
structure increases in length. From five to seven ridges are con-'
structed along its sides and top as a result of the loops formed in
spinning. When the canopy is over half completed, the caterpillar
crawls into the cocoon. It then makes a 180° turn and moves in the
opposite direction until it reaches the other end of the silken base.
In this reverse situation, the larva weaves the front end of the co-
coon in the same way as the other part was constructed. As the two
ends come together, they are joined by a flat sheet of silk spun from
the inside of the cocoon. This joint was easily seen in the finished
cocoon by the writer, since the ribs of the outer layer did not line
up perfectly.

When both ends of the cocoon were joined, an inner lining was

spun, making the inner chamber. One partition was formed at one end

37
of the inner chamber. The insect was thus compressed into a snug com-
partment, but when it moulted for the last time and transformed into a
pupa, it shrank to about half the length of the last instar. Snodgrass

(1922) discusses a similar construction of the cocoon of Bucculatrix

 

pomifoliella.

 

Description of the Pupa

 

The pupa itself as observed in the field is flexible only at the
ninth and tenth segments of the abdomen. The head of the pupa ends in
a sharp beak-like point which penetrates through the silken strands of
the cocoon just prior to adult emergence. Lateral spines on the ninth
segments catch hold of the inner cocoon and help in forward movement
of the pupa. Snodgrass (1922) also noted this phenomena in B.

pomifoliella.

 

Pupal Emergence

 

As seen in Figures 1 and III, the insect overwinters in the pupal
stage, emerging as a first generation adult in April and early May.
When ready to emerge, the insect is in the pre—imaginal stage. It
works its way forward using spines on the tenth abdominal segment.
When about one-half to three-fourths of the chrysalis is exposed, the
body is held at a 30° - 40° angle from the cocoon. The pupal skin
splits at the juction of the vertex of the head and pro-thorax and
also longitudinally through the prothorax and mesothorax of the venter.
The front part of the head; antennae, and eye pieces remain attached
together as a part of the chrysalis. Snodgrass (1922) describes the

emergence of B: pomifoliella.which occurs in a similar manner.

 

38

Adult Stage

 

In 1959 in Baker woodlot, first generation moths emerged in late
April and early May. Second generation moths began to appear in late
July and early August (Figures I and IV). Figure IV shows the differ-
ence in rates of emergence between overwintering and summer genera-
tions. A regression line was sight fitted in order to smooth out day
to day variations due to sampling error. Table 4 expresses emergence
and mortality as percent of the total. There was a low but consistent
emergence recorded from March 25 to April 23. Emergence increased at
a rapid rate in numbers of adults after April 30, whereas the summer
generation emergence rate was fairly consistent throughout. At the
time of adult activity, adults were seen on the trunks of trees in the
infested area, particularly on species fed upon by the larvae.

During daylight hours, the adults were seen to reSt quietly on
the surfaces of leaves and bark of red oak, beech and other large di-
ameter trees. When present on a leaf, the adult was always found un-
derneath and near the edge. This peculiar habit is also characteris—

tic of B. chrysathamni as discussed in the literature review; The

 

majority of the adults appeared to rest on the lower part of the trees
during the daylight hours. They usually remained motionless during
this time. One pair was seen to be in copulation at midday in early
May. When disturbed, they flew very rapidly and continued to dart
about, 5 to 10 feet above the ground until they were lost from View.
As a result of these observations, it would Seem that the moths

remain near the ground during the day and go up into the trees at

39

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41

about dusk. Although they are not found in direct sunlight, there was
no apparent preference for the north or south sides of the trees.

Oviposition was not observed in the field so it must be assumed
to take place after dark. No adults were found on the leaves of the
host tree during daylight.

Since most of the first generation development was not observed,
an attempt was made to reconstruct it from second generation data.'
Enough actual observations were obtained on first generation phenom-.
ena, however, to state that first generation adult emergence took place
in April, with egg laying following probably in the latter part of the
same month. Mining was noted in early to mid-May and emergence from
mines began around mierune. The order of events is similar for both

generations and both are shown in Figure I.

HOST PREFERENCE AND RANGE

Bucculatrix ainsliella larvae fed only on northern red oak,

 

Quercus rubra, in Baker woodlot, as far as the author could determine.

 

Needham 35.21' (1923) and Tomlinson (1952) list B. ainsliella as a

 

feeder on a variety of oak species. —According to Drooz (1960) it has

been seen to feed on red oak and chestnut oak, Quercus montana Willd.

 

No other information to this effect has been found. White oak, Quercus
alba, was growing with red oak in a major part of the experimental
area, both in understory and as a dominant. Some swamp white oak,

Quercus bicolor Willd., was scattered throughout the woodlot but none

 

was found within the experimental plots.
According to Harlow 23.21' (1950), northern red oak is found on
sandy loam soils in mixture with other northern hardwoods and with

white pine, (Pinus strobus.L).Northern red oak occurs from southern

 

Nova Scotia, south through South Carolina, westward through northern
Mississippi to eastern Oklahoma and northward through the middle of
Minnesota. Within this range only a small area in the Allegheny Moun-
tains of New York lacks this tree species (Harlow at 21. 1950).
Ainslie, according to Murtfeldt (1905), collected the first reported

specimens of B. ainsliella near Rochester, Minnesota in 1905.

 

In 1951 according to McGugan 33 gl., noticeable foliage injury by
first generation larvae was recorded by the Canadian Forest Insect
Survey in red oak stands in Lincoln, Welland, Elgin and Middlesex

Counties in the Lake Erie district of Canada. In 1952, it was again
42

43
recorded as being present throughout the Lake Erie district but
causing less damage than the previous year. In 1958 MCGugan et 31.
(1958) records that this species was collected for the first time in
western Quebec. This may be an indication of its spread eastward, or
at least, its rise in considerable numbers without detection. Tomlinson

(1952) states that B. ainsliella had been present near Boston during

 

the previous two or three sumers. Drooz, (1960),,reported heavy feed-
ing on red and chestnut oak in Bradford Co., Pennsylvania in 1959. To
the best of the writer's knowledge, there are no other reports which
indicate its presence elsewhere.

Since red oak and chestnut oak are endemic to the eastern part of

the United States, the strong specificity exhibited ble. ainsliella to

 

its host suggests that it is a native insect.

To determine its feeding habits on other tree species, nine free
feeding specimens were collected in the field on red oak and placed in
a rearing cage with three potted species of trees; sugar maple, £235

saccharum, American beech, Fagus grandifolia, and white oak, Quercus

 

alba. Three larvae were placed on each plant. After twenty four

 

hours the only visible larvae were found on red oak along with some
evidence of leaf feeding. Two days later only one larva was seen to be
feeding and this on the upper surface of a white oak leaf. The missing
caterpillars were later found on the soil of the potted plants of dif-
ferent species. Of the ten larvae, four had already formed the second
moulting tent and each of the other six had moulted at least twice out-
side of the mines. If these limited observations are representative

of larval behavior under natural conditions, the caterpillars may feed

44
at least.brief1y on white oak. Although it was not possible to make
such a study here, host preference might be determined by oviposition
preference and survival on the respective hosts. In the efforts made
here, larvae were replaced on the various plant species when they were
observed to have wandered or dropped off. This was continued until
they fed upon the leaves or died. In nature it is conceivable that
larvae will starve to death in the midst of food which would keep them
alive but which for some reason, they will not eat. This may be true

for B. ainsliella if it is removed from its preferred host but comes

 

in contact with other species of Quercus. Drooz (1960) reports B.

ainsliella feeding heavily on chestnut oak. Perhaps if certain other

 

species of trees are presented to this insect, the larvae may feed
freely on them.
Figure V compares the mean rates of increment growth of beech,

Fagus grandifolia and northern red oak Quercus rubra. Both increase

 

 

and decrease of the growth rates of both species appear similar. In
1959, there is a strong decrease in the increment growth rate of the
two tree‘species while in 1958 there appears an increase of growth.
Although the infestation of this insect has occurred for at least two
years, 1959 and 1958, there appears to be no correlation of its pre-

sence to the decrease in growth of the red oak.

45

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FACTORS AFFECTING ABUNDANCE

Some of the factors which have a bearing on the abundance and rate
of increase of this insect deserve consideration. These may be grouped
under food supply, climate and natural enemies. Man has not yet played
any important role in direct control of this species. The preferred
food plant, red oak, is fairly abundant around the central and eastern
parts of the United States and Canada, but so far no appreciable effect
on the growth of the oak has been reported. Between outbreaks, the
larva is seldom reported. Red oak is an important component in the
northern deciduous forest and according to little, UQSJD.A. Yearbook
(1949), is used as an ornamental tree also. During an outbreak, when'
the larvae completely skeletonize all the foliage in the main canopy,
the oaks are not killed, even by repeated attacks. This may be due to
the fact that feeding is heaviest after most of the tree growth is
completed in any given year. As observed in this study, most leaf
injury occurs during the months of August and September at a time when
trees have passed through their/most active growth period.

An early spring defoliation by other insects would affect the sure

t .
vival of late feeding Bucculatrix since their food supply would become

 

scarce.

B. ainsliella minings in the first generation are confined to the

 

outer parts of the leaves, while later mines are located more centrally.
All observations made during this study indicate that first generation
feeding is light and such defoliation was not important in limiting the

numbers of the second generation.
46

47
No data were obtained on the effect of climate on survival of

this species. It may be expected that B. ainsliella pupating on the

 

trunks and branches above the snow line would be adversely affected by
extremes of weather. Of 1347 overwintering pupae observed in the lab-
oratory, 996 or 74.0 percent had died. Whether this is normal or not
cannot be determined unless several counts in successive years are
made. Of the dead, 273 or 20.4 percent had died in the prepupal stage
(Table V), suggesting that they might have been affected by an early
cold snap. There is no evidence in any of these observations to sug—
gest that climate is a major factor responsible for the periodic rise
and fall in abundance.
.

That parasites and predaceous enemies of this insect are impor-

tant in its numerical increase and decrease is suggested by the abun-

dance of the following species of parasites that were obtained from

both larvae and pupae.

 

 

 

 

Family Eulophidae Stage of Host
17 Cirrospilus flavicinctus Riley . . . . . pupae
2 Cirrospilus flavicinctus Riley . . . . . larvae
9 Pnigalio maculipes (wad.) . . . . . . . pupae
3 Pnigalio maculipes (wad.) . . . . . . . larvae
Family Braconidae
l Apanteles ornigis Weid.. . . . . . . . . pupae

 

Overwintering pupae that had not emerged were examined and very
few dead parasites were found. Of 1346 pupae, only 351 or 26.0 per—
cent produced adult moths; whereas of the parasitized pupae, 33 in all,
29 or 2.1 Percent of the total number of pupae produced live parasites of

hymenoptera, giving a rate of survival of 87.9 percent (See TableIV).

48
It may also be mentioned here that the parasites emerged about a week
earlier than did the moths under laboratory conditions at room tem-
perature. Most of the parasitized pupae had their silken cocoons
stained light to dark brown with the body contents of the host. The
parasites observed occurred singly in their host, although on one oc-
casion two larvae were observed feeding on one caterpillar in a second
instar moulting tent.

In addition to parasitism noted in the above two stages, there

was evidence of some parasitism in the mining stage. This was noted
only once, however, perhaps because of the protective leaf layer.

Another important enemy of Bucculatrix larvae, perhaps more im—

 

portant than the above mentioned parasites, were the various species
of ants and other predaceous insects which captured the larvae on the
oak leaves. Ants had frequently been observed carrying free feeding
stages of larvae down the bark of red oak in the latter part of August.
During the course of one observation period on one tree trunk, half of

the food carried by the ants was estimated to be B. ainsliella. One

 

ant was observed tearing a partially built moulting tent apart, appar—
ently in an attempt to get at the larva. The mortality of cocoons
found on the ground as discussed previously, may have been due to simi-
lar predation early the previous fall.

Birds may be another serious predator. The presence of free feed-
ing larvae occur when many of the native birds are nesting and there-
:fore seedreating species may conceivably find the larvae a source of-

food.

49

As can be seen in TablelV, only 2.1 percent of the overwintering
pupae were parasitized. This compares with about 15 percent parasitism

of the summer generation. This could be interpreted as an indication

of increasing parasitism from one generation of ainsliella to the next.

 

Certain undetermined environmental factors, may prevent the de-

velopment of B. ainsliella beyond the mining and pupal stages. Some

 

mining larvae had died but causes of death were unknown. Many of the
overwintering pupa that were examined had apparently died just before

dissection since the body tissues were still moist.

CONTROL

The timing of control for this insect can be inferred from the
life history data presented here. In order to have an insecticide
present during the free feeding stage, trees should be sprayed about
the middle of June for the first generation and the last part of Au?
gust into the middle of September for the second generation. At
this time, the larvae can be seen free feeding or the tiny moulting
tents can be seen on the undersides of the leaves. Applying an in-
secticide while the insect is in the mining stage would not be suc-
cessful since the miner is well protected by the leaf surfaces.
Since the larvae feed on the lower side of the leaves, however, any

insecticide should be directed up into the foliage, if possible.

50

SUMMARY

The literature pertaining to the genus Bucculatrix has been

 

briefly reviewed and biology and habits of some of the more important
species of this genus have been presented. Taxonomically the genus is
placed in the family Lyonetiidae.

1. Two generations of Bucculatrix ainsliella were observed in Michigan

 

in 1959. Eggs were laid on the underside of red oak leaves from mid
to late May and again in the latter part of July. These eggs hatched
‘within two weeks.

2. Mining occurred from midrMay to mid—June and again from mid-July
to late September. The larvae mined in the leaf for at least one in-
star. The mining period lasts from 5 to 6 weeks in each generation.

3. Free feeding occurred from late May to late June and again from
late August to middle October.

4. The number of instars was estimated by measuring head capsules in ‘
both mining and free feeding stages. At least two instars occurred
outside the mine, as indicated by the presence of moulting tents. Lar-
vae lived for about 10 weeks.

5. Description and formation of the cocoon was discussed. The insect
overwintered in the cocoon stage, with adults emerging in April. Sec-
ond generation adults emerged from late July to early August. Cocoons
of the overwintering generation were found on bark and twigs of trees;
while summer generation cocoons could be found on foliage, twigs and

bark.

51

—I.I..

52
6. First generation adults were found in May and second generation
moths were present from July to early August.

7. .B. ainsliella prefers northern red oak as a host plant but may

 

feed on white oak to a limited extent.

8. There is a very high overwintering mortality of the insect, possi—
bly due to temperature extremes.

9. Parasite emergence from parasitized cocoons was on the order of 87
percent. Presumably the host was parasitized chiefly in the free feed-

ing stage.

 

10. Ants were frequently observed preying on B. ainsliella. On oc—

casion Coccinellid larvae were observed feeding on B. ainsliella cater-

 

pillars.
11. A species of brown fungus occurred on dead pupae but whether this

was responsible for the death of the insect was not known.

BIBLIOGRAPHY

Braun, A.
1920 New Species of Lyonetiidae (Microlepidoptera). Ent. News 31:

1925 Microlepidoptera of Northern Utah. Trans.Amer. Ent. Soc. 51:
183-226.

1927 Descriptions of New Microlepidoptera. Trans. Amer. Ent. Soc.
53: 191—199.

1930 Netes on New Species of Microlepidoptera from Mineral Springs
Region of Adams County, Ohio. Trans. Amer. Ent. Soc. 56:
1-17.

1956 A New Species of Gall Forming Bucculatrix from Florida
(Lepidoptera: Lyonetiidae). Ent. News 67: 69-70.

 

Breland, B. P. and L. H. Schmitt
1948 Biology of Two Sunflower Gall Makers. Ent. News 59: 225-234.

Brown, L. R.
1953 Some Insects Injurous to Western Shade Trees. Proc. Nat.
Shade Tree Conf. 29: 230-240.

Busck, A.
1919 A New Species of Bucculatrix Injurous to Hollyhock (Lepidop-
tera). Proc. Ent. Soc. Wash. 21: 109-110. '

Chambers, V. T.
1882 thes on the Larvae of Bucculatrix ambrosiaefoliella. Can.
Ent. 14: 153-160.

 

Clemens, B. .
1872 Tineina of North America. London. Ed. T.H. Stainton, 271 pp.

Craighead, F. C.
1950 Insect Enemies of Eastern Forests. United States Dept. Agri.
Misc. Pub. No. 657. 658 pp.

Drooz, A. T. ed.
1959 Pennsylvania Forest Insect and Disease Summary for 1959.
Forest Advisory Services, Harrisburg, Penn. 1960.

JDyar, H. G.
1890 Number of Moults of Lepidopterous Larvae. Psyche. 5: 420-422.

53

54

Essig, E. O.
1926 Insects of Western North America. Macmillan Co. New York.

 

750 pp.
Felt
1921 A New Species of Bucculatrix. N. Y. State Mus. Bull. 23:
227-228.

Folsom, V. W.
1932 Insect Enemies of the Cotton Plant. United States Dept.
Agri. Farmers Bull. No. 1688: 14-15.

Forbes, W. T. M.
1923 The Lepidoptera of New York and the Neighboring States.
Cornell Univ. Agri. Exp. Sta. Mem. 68. 729 pp.

Fracker, S. B.
1915 The Classification of Lepidopterous Larvae. Ill. Bio. Mono.
Vol. 2: No. 1.

Friend, 3. F.
1927 Biology of a Birch Skeletonizer. Conn. Agri. Expt. Sta.
Bull. No. 288: 395-486.

Harlow, William M., Ellwood S. Harrar
1950 Textbook of Dendrology. McGraw—Hill Co., Inc. New York:
555 pp.

Hooker, Jesheph D. and Daydon Benthen
1893 Index Kewensis.Clarendon Press. Oxford. England. 728 pp.

Hutchings, C. B.
1925 Birch Leaf Skeletonizer. 56th Annual Rept. Ent. Soc.
Ontario: 69-71.

Lamburt, A.
1943 Insect and Disease Survey Report. Can. Dept. of Agri. 8,
1942.

Little, Elbert L._
1949 To Know the Trees 12 United States Dept. Agri. Yrbk. 1949.
944 pp.

Martineau, R.
1958 Province of Quebec. Can. Dept. Agri. Annual Report of the
Forest Insect and Disease Survey: 30-37.

McGugan, B.M., W.H. Haliburton, and J.E. MacDonald
1951 Province of Ontario. Canadian Dept. Agri. Annual Report For-
est Insect and Disease Survey: 41—67.

55

1952 Province of Ontario. Canadian Dept. Agri. Annual Report For-
Insect and Disease Survey: 41-67.

Miller, P. A. and C. Brown
1951 Problems of Oak Trees in Southern California. Proc. Nat.
Shade Tree Conf. 27: 283-290.

Merrill, A. W.
1927 Observations on Bucculatrix gossypiella: A New and Important
Cotton Pest. JOur. Econ. Ent. 20: 536-544.

 

Mosher, E.
1916 A Classification of the Lepidoptera Based on Characters of
the Pupa. Bull. Ill. State Lab. Nat. Hist. V01. 12. Art. II.

Murtfeldt, M.
1905 A New Species of Bucculatrix. Can. Ent. 37: 218-219.

 

Needham, J. G., S. W. Frost and B. T. Tathill
1928 Leaf Mining Insects. Williams and Wilkins Co., Baltimore:
351 pp.

Needham, J. G.
1948 A Bucculatricid Gall Maker and its Hypermetamorphosis. JOur.
N. Y. Ent. Soc. 56: 43-50.

Snodgrass, R. E.
1922 The Resplendent ShieldeBearer and Ribbed-Cocoon-Maker.
Smithsonian Rept. Pub. No. 2641: 496-508.

Stainton, H. T. ‘
1867 Natural History of the Tineina. John Van Voorst. London Vol.
7. Bucculatrix: 135 pp.

 

Tomlinson, W. E.
1952 Some Insect Pests of New England Trees. Proc. Nat. Shade
Tree Conf. 28: 85—88.

Plate 1 Cocoon of Bucculatrix ainsliella on underside of red oak leaf.

Plate 11 Adult of B. ainsliella (wing expanse - 8 m.m.)

 

57

 

Plate III Eggs of B. ainsliella: A - Partially developed egg. B - De-
veloped egg showing black head capsule. C - Hatching larvae filling
egg shell with frass.

 

lfv
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Plate IV First moulting tent of B. ainsliella.

 

Plate V Second moulting tent of B. ainsliella.

Plate VI Larva of B. ainsliella constructing cocoon.

 

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HICHIGRN STRTE UNIV. LIBRR