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0-169

This is to certify that the
thesis entitled

Studies of Lyctid and Scolytid
Beetles Infesting Seasoning Lumber

presented by

Garrit J. Lugthart, Jr.

has been accepted towards fulfillment
of the requirements for

Date W51.

 

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Du“.

——

 

STUDIES OF LYCTID AND SCOLYTID BEETLES

INFESTING SEASONING LUMBER

By

GARRIT J. LUGTHART, JR.
‘“

A THESIS

Submittedto the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for’the degree of

MASTER OF SCIENCE

Department of EntomOIOgy

1951

THEszs

ACKNOWLEDGMENTS

I would like to express my sincere appreciation to the
members of the Department of Entomology for their suggestions,

criticism, and interest during the course of this problem.

8113893

TABLE OF CONTENTS

I. INTRODUCTION
II. REVIEW OF LITERATURE
The Powder—post Beetles, Family
Lyctidae

The Ambrosia Beetles, Monarthrurn mali

 

and _1yI_. fasciatum

 

III. METHODS AND PROCEDURES
Survey of Insects from Sawmills and
Lumberyards
The Rearing of Lxctus sp.

Infestation Experiments with Monarthrurn

 

mali (Fitch) and M. fasciatum (Say) .

 

IV. PRESENTATION AND DISCUSSION OF DATA .

Survey of Insects from Sawmills and
Lumberyards
Rearing of Lyctus sp. .

Infestation Experiments with Monarthrutn

 

mali (Fitch) and _l\_/I_. fasciatum (Say) .

 

Page

ll

15

15

16

20

26

35

39

V. SUMMARY AND CONCLUSIONS

LITERATURE CITED

iv
Page
44

47

I. INTRODUCTION

In the fall of 1950 investigations were begun on the
powder—post beetles of the family Lyctidae.

This t0pic was suggested as a thesis subject because
of the increasing importance of these insects to the hardwood
industry. Thousands of board feet of seasoned lumber, and
even more important because of the man—hours involved, large
quantities of tool handles, gunstocks, and other manufactured
items, are lost annually to this pest. A factor increasing
their importance is their habit of attacking only the sapwood.
Since most of the timber being cut in the northeastern United
States is either second or third growth, larger amounts of
seasoning hardwood lumber are subject to attack.

At the outset of this project two goals were set: a sur—
vey of the insects infesting seasoning lumber, and a determina—
tion of the effects of various humidities on the life cycle of the
powder—post beetle.

Attempts to secure relatively large p0pulations of powder-
post beetles for the humidity control experiment failed. After

these failures efforts were directed toward finding a successful

2
method of rearing these beetles in small chambers suitable for
the originally intended humidity experiment.

From the preliminary work on the survey a high inci—
dence of scolytid damage was noted in seasoning lumber at
various sawmills. Because of these findings a third problem
was investigated. In most cases it was obvious that the infes—
tation had occurred sometime before the 10gs had been sawed.
Many adult beetles were removed from samples checked in the
laboratory. Examination of the life cycle of these beetles
showed that they overwinter in the adult stage. If infested
timber were milled and piled for air—seasoning in late fall
or during the winter, the adults would emerge in early Spring
to seek new locations for their tunnels. With these facts in
mind, it seemed possible that the beetles could re—infest the
same lumber which would still be of a correct moisture con-
tent, or lumber free from scolytid injury that had been cut and
stacked at approximately the same time. An experiment was
conducted to determine if scolytids would re-enter wood sam—

ples of a similar moisture content to those from which they

had emerged.

II. REVIEW OF LITERATURE

The Powder—post Beetles,
Family Lyctidae

The order ColeOptera has been studied systematically
by many workers. ColeOpterists have revised the system of
classification according to the form of the antennae and tarsi,
or based systems on phylogeny or genitalia, or combinations
of these characteristics. The revisions of the order made by
Le Conte and Horn (1883) listed the lyctids as a subfamily of
Ptinidae. Fall (1905) in his revisions of the family Ptinidae
raised the subfamily Bostrichinae to family status, and suggested
that Lyctinae might be included in the family Cucujidae. Lyc—
tinae was classified as a subfamily of Bostrichidae by Blatchley
(1910). Acc0rding to Leng (1920), Kraus suggested the family
standing for the lyctids. Most of the recent publications fol-
low the systematic arrangement of Leng's Catalogue of ColeOp—
tera (Table I).

The work of these insects may be recognized by the
numerous minute holes which are made by the emerging adults,

and the presence of fine white dust-like borings.

 

 

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Because of the talc—like dust made by the larvae, they
are popularly known as the powder—post beetles. Some authors
restrict this common name to the family Lyctidae (Essig, 1942),
while others use it more loosely. Dorn gt _a_l_. (1936) and Gra—
ham (1929) use it for the representatives of four families,
Ptinidae, Anobiidae, Bostrichidae, and Lyctidae, of the super—
family Ptinoidea. They refer to the family Lyctidae as being
the most typical, and call them the "true powder—post beetles."
Comstock (1948) used the common name for the family Bos—
trichidae, and stated that the members of Lyctidae resemble
the powder—post beetles. In the latest publication by Craig—
head (1950) the common name, powder—post beetles, is used
for both the families Bostrichidae and Lyctidae. However, the
former is designated as the "large powder—post beetles" and
the latter as the "Lyctus powder—post beetles."

Blatchley's (I910) description stated that the adult beetles
are elongate and slender and have a prominent head, slightly
narrowed behind the eyes, and not covered by the thorax. The
latter characteristic immediately separates this family from
related ones. The thorax is trapezoidal in shape with a fine

lateral margin. The antennae are eleven-segmented, with a

rounded club composed of two segments. The anterior coxae
are entirely enclosed and separated by the prosternum; the
posterior ones are widely separated. The first ventral seg-
ment of the abdomen is much longer than any of the others.

Fisher (1940) described the larvae as curved, wrinkled,
yellowish—white, with brown jaws, scarabaeoid in form. The
Spiracles on the eighth segment are much larger than those on
the other segments, appearing as two brown oval spots. They
have three pair of minute three—segmented legs.

According to Mallis (1945), Gaham and Laing described
the egg as being "white, cylindrical, shiny, granular, and
about 0.8 millimeters long. There is a small slender strand
at one end, behind which the surface is striated lengthwise."

Fisher (1940) outlined the life history of Lyctus, which
is quite typical of the entire family. He stated that under nat—
ural conditions the normal period of deveIOpment from egg to
adult is approximately one year. The. adults begin to emerge
in the spring, first appearing about April. Females lay thirty
to fifty eggs, placing them within the pores on the surface of
the wood. The larvae, which hatch in eight to ten days, tun—

nel into the wood. At first they are said to tunnel with the

grain, but later to work through the wood in all directions.
When the larvae are full grown, they bore toward the surface
of the wood, making a pupal chamber just below it. In emerg—
ing, the adults have been known to bore through heartwood,
varnish, paint, glue, and even metal coverings, such as lead
and silver.

It has been observed (anon. , 1939) that Lyctus paral-

 

leloPipedus (Melsh) deve10p from egg to adult in approximately

 

three months under ideal southern conditions. Snyder (1926)
found that under indoor conditions deveIOpment may take place
more rapidly and eggs may be deposited earlier.

The economic importance of these insects has been in—
creasing constantly during the past three decades. Transpor—
tation of hardwood timber or finished hardwood articles has
distributed the beetles to all parts of the world. The estimated
damage in the United States is approximately eighteen million
dollars per year (anon. , 1939).

Lumber inspectors have great difficulty detecting all
lyctidwinfested lumber, eSpecially during the first weeks of an
initial infestation when the eggs and young larvae are hidden

within the surface pores. Inexperienced observers when

8
inspecting for powder—post damage often notice the character—
istic dust, but fail to find the emergence holes because of the
adult’s habit of emerging from the underside of the boards.

Any hardwood is liable to lyctid attack. However, they
confine their injury to the sapwood, the portion of the tree con-
taining the largest amount of starch which is their principle
food. It has been stated that some species of beetles may be—
gin their destruction before the timber is thoroughly seasoned,

and that Iiyctus EralleIOpipedus will attack lumber above a

 

moisture content of 15 percent (anon. , 1939).

Panshin (1949) stated that well air—seasoned lumber con—
tains from twelve to eighteen percent moisture, while "kiln—
dried" lumber implies less than ten percent moisture.

According to Craighead (1950), lumber may be seasoned
in the yard or shed nine months or more in the North without
fear of Lyctus attack. Kiln—dried or thin—dimensioned air—
seasoned hardwood stock is subject to attack in less than three
months.

Snyder (1938) recommended: (1) inspection of lumber
annually; (2) prevention of accumulation of waste wood; (3)

arrangement of sapwood material by species and age for ready

examination; (4) disposal of the oldest stock first since it is
the most susceptible to attack; and (5) inspection of all newly
arrived stock to prevent introduction.

It was found in 1939 that the immersion of unfinished
lumber for ten seconds in a five percent water solution of

borax protected it from Hctus paralleloPipedus but not 1.1.

 

planicollis (anon., 1939). In 1940 successful control of lyctid

 

beetles by fumigation with methyl bromide was reported
(Christian, 1940).

Snyder and St. George (1924) found that kilns Operated
by live steam, in which wood up to one inch thick could be
heated to a temperature of 1300 F. for one and a half hours,
killed the insects. This method does not prevent subsequent
attack and is not recommended for wood requiring great struc-
tural strength or a fine finish, since steaming may weaken and
discolor the wood.

.It is reported that stock cultures of Lyctus beetles were
reared by the hundreds in large tins covered over with cheese-
cloth and confined in an incubator which was held above 260 C.
and at 75 percent relative humidity. The wood contained 10 to

o
15 percent moisture at 210 to 27 C. A life cycle was completed

10
in less than six months under these conditions (anon. , 1939;
Christian, 1940).

Hansens (1944) reported the use of sulfuric acid to main—
tain constant humidity for experiments on the body louse. The
acid was placed in the bottoms of battery jars, and the solu—
tion covered with screening. The jars were covered with large
petri dishes, and sealed with "Celloseal" or vaseline..

Wilson (1921) found that the moisture content of most
materials varies only a small amount with moderate changes
in temperature, providing the relative humidity is kept con-
stant. Both Wilson and Hansens gave tables for percentages
of sulfuric acid required to give definite humidities.

Buxton and Mellanby (1934) gave a convenient method
to make a range of dilutions for different hurnidities by use of
a sulfuric acid stock solution. A table is given for the concen-
tration of stock solution and water to use for various relative
humidities.

Saturated solutions of salts may also be used to maintain
definite relative hmnidities. Martin (1939) lists salts and the
relative hurnidities they will give when used as saturated solu—
tions. A similar list may be found in the Chemistry and Physics

Handbook.

ll
Peterson (1934) reported that within an insect cage the
relative humidity is determined to some extent by the construc—
tion or covering of the cage.

The Ambrosia Beetles, Monarthrum
mali and M. fasciatum

 

 

According to Leng (1920) the classification and synonomy

of the genus Monarthrum is as follows:

 

Order Cole0ptera
Suborder Rhy‘nch0phora
Superfamily Scolytoidea
Family Scolytidae
Ipidae (Swaine)
Subfamily Ipinae
Tribe Corthylini

Genus Monarthrum (Kirsch), 1866

 

Pterocyc lon (Eichhoff) , 18 68

 

Species fasciatmn (Say), 1825

 

Species mali (Fitch), 1855
These Species belong to a group of scolytids which have
been classed tOgether because of similar feeding and living

habits, rather than anatomical likenesses, and are pOpularly

12
called ambrosia beetles. This common name has been derived
from the fungi ambrosia on which the adults and their larvae
feed. Other names, such as "timber beetles," "shothole bor—
ers," and "pinhole borers," have been given to the group be—
cause of the nature of their injury.

Blatchley (1916) characterized the tribe Corthylini to

which the Genus Monarthrum belongs as havingi

 

Pronotmn and elytra without scales, commonly
glabrous or sparsely pubescent; abdominal sternite seven
with posterior margin rarely rounded; anterior tibia broader
toward apex or serrate on outer margin; pronotum with
anterior dorsal area commonly rugose; head concealed
from above; anterior tarsi with joint three simple.

The genus is distinguished by the cylindrical first pal—
pal joint, emarginate elytral apex, and two—jointed funicle.

M. fasciatum is slightly larger than M.ma1i and may be dis—

 

tinguished by a pale yellow band across the middle of the wing
covers.

Swaine (1918) described scolytid larvae as, "always leg—
less, whitish in colour, with darker, strongly chitinized head
and mandibles, and with the thoracic segments distinctly larger
than the others, in the true dark beetles."

No direct information could be found on the life histories

of these two species. Scolytids in general transform from the

l3
pupal to the adult stage in the late summer or in the fall.
Most species remain in their host throughout the winter, and
emerge the following spring (Craighead, 1950).

These species are monogamous. The female starts the
gallery which extends into the sapwood. Craighead (1950) re—
ferred to the galleries as compound ambrosial burrows. They
differ from simple ambrosial burrows in that the parent beetles
make niches in the upper and lower sides of the tunnel for the
eggs. As the larvae grow they deepen their pits. The parent
beetles attend and feed the young by removing debris and put-
ting fungus in the mouth of the larval niches.

Craighead (1950) claimed that bark beetle damage to
utilized timber is of much less importance than that by other
groups of insects, such as the lyctids and termites.

Snyder (1927) reported that adult ambrosia beetles
caused "pinhole" damage in freshly felled green sawed logs
(with or without bark), and in any green or partly seasoned
lumber. Graham (1929) also stated that ambrosia beetle injury
is not always confined to freshly cut or killed trees, but that
they will attack green lumber, particularly the slow drying

large dimension stock. Experiments conducted in the South

l4
, (Christian, 1939) substantiated the statements of Snyder and
Graham. This work showed that the adult beetles caused the
damage by boring into the wood. The only boring done by the
larvae is in the enlarging of their small niches. The adults
are attracted to freshly felled logs and green lumber, which-
under favorable conditions for attack may be severely damaged
within a few days time, and in a few weeks reduced in value
to the extent of fifty percent or more. Christian also found
that the beetles are able to survive in the wood only while the
moisture content is high. Consequently the damage ceases
before the timber is thoroughly seasoned.

Chamberlin (1949) stated that M. fasciatum and M. 3131i
are reported to be very destructive to gum in Louisiana, at-

tacking green lumber as well as fresh 10gs.

III. METHODS AND PROCEDURES

Survey of Insects from Sawmills
and Lumberyards

The insects for this survey were collected during the
fall of 1950 and spring of 1951. Collecting was done at various
sawmills in lower Michigan and at retail lumberyards in the
Lansing area. Storage sheds and other buildings, as well as
the lumber and waste piles, were inspected for infestations.
Samples of lumber showing signs of insect damage were brought
to the laboratory for a more careful examination.

Attempts were made to rear some of the larval forms
found infesting the seasoning or seasoned wood. Infested boards
were cut to convenient sizes and placed in one of three types
of containers. The cages consisted of glass lamp globes cov—
ered with cheesecloth and set on glass terraria, small battery
jars covered with cheesecloth, or c0pper mesh cages enclosed
on the ends by screening or terracotta germination dishes. The
cages were placed in a constant temperature room (240 C.).

Identification of the insects taken was done by the author,

except when the genus and species names of the lyctid or scolytid

16
beetles were desired. These insects were sent to the United
States National Museum. The wood from which insects were
removed was identified by a faculty member of the Michigan

State College Forestry Department.
The Rearing of Lyctus sp.

Two methods, sulfuric acid solutions and saturated salt
solutions, were investigated for maintaining constant humidi—
ties. The use of salt solutions was decided upon because of
the ease with which they may be handled. The beetles were
to be raised at a temperature of approximately .240 C. Table
11 gives the range of humidities to be used and the salts nec-
essary for the given percentages of relative humidity.

It wasplanned to enclose 15 to 20 beetles in large bat-
tery jars with a piece of hickory showing no previous infesta—
tion. The salt solutions were to be placed in a glass terrarium
and covered with a fine mesh screen. The jars were to be
covered with glass and sealed with vaseline.

In an attempt to secure the number of beetles needed
for the experiment a rearing method similar to that described

by Christian (1940) was used. Infested pieces of hickory were

17

TABLE II

SALTS AND THE RELATIVE HUMIDITIES GIVEN
WHEN USED IN SATURATED SOLUTIONS

 

 

 

Percent

Relative Salt

Humidity
9 H3PO4 . (1/2)H20 Saturated Solution
31 CaClz - 6HZO H u
43 K2C03 - ZHZO H n
51 Ca(NO3)Z - 41120 n n
71.2 NH4C1 and KNO3 " H
81. l (NI-I4)ZSO4 n n
93 NH4H2PO4 " H

 

 

placed in glass lamp globes, set in glass terraria, and covered
with cheesecloth. A small bottle of water with a cloth wick
was enclosed to raise the humidity inside the cage. Three
cages were placed in a constant temperature room, which was

held at approximately 240 C. and at a relative humidity of

18
about 60 to 65 percent. One cage was left at room tempera-—
ture without a water bottle for moisture, that is, at conditions
similar to those the insects would be exposed to in an average
home or heated building. Occasional checks were made of all
.wood samples to determine the condition of the larvae.

Working on the assumption that if smaller pieces of
wood were used, the internal environment of the wood might
be closer to the external environment, infested wood was chOpped
into small irregular pieces and placed in two 750 m1. jars.
Two test tubes of water were enclosed in each for moisture.
One jar was covered with cheesecloth, the other with an 'in—
verted petri dish.

Approximately three weeks after the chips had been
enclosed, it was noted that mold had developed on the chips
in the jar covered by the petri dish. This growth of fungi
within this closed container raised the question: Could the
method described above for rearing beetles at various percent—
ages of relative humidity be done in small enclosed containers?
In an attempt to answer this question new stocks of wood in—
fested with Lyctus beetles were obtained. The wood was ex—

amined to determine the stage of deveIOpment of the insects.

 

 

 

 

Figure 1. Large battery jar type
cage; water; hickory.

l9

20
The method used in this rearing attempt was as originally
described. Four rearing containers were used (Table IV).
Water was used in three for humidity control. In one of these
three cages a small coil Operated humidity gauge was enclosed.
In the fourth cage a saturated solution of potassium nitrate and
ammonium chloride was used to give a relative humidity of
71.2 percent.

Infestation Experiments with Monarthrum mali
(Fitch) and M. fasciatum (Say)

 

The object of these tests was to find if M. fasciatum
and M. 193.11 would enter partially seasoned, milled lumber.
The containers used were glass lamp globes set on glass ter—
raria and covered with cheesecloth. The containers with en—
closed wood were placed in a constant temperature room (240
C.). Under these conditions the wood would dry more rapidly
than in the natural outdoor environment. Two methods were
used to increase the moisture within the jars. In three con-
tainers small bottles with cloth wicks were used, and moist
sand was used in three others. The sand was'sterilized and
moistened with capper sulfate solution to prevent fungi spores

from germinating. The enclosed wood was placed on inverted

21
petri dishes to keep it from absorbing moisture from the
sand.

The following is an outline of the type of cages used,
kind of wood enclosed, and the species of scolytid beetle in—

volved,

Containers with moist sand:

Cage 1. Two 2" x 4" x 5" pieces of non—infested
soft maple were enclosed with ten adult beetles,
M. _r{1_a__L_l_i_, taken from the same stock.

Cage 2. A 2" x 4" x If)” piece of-soft maple in—
fested with M. {gait was enclosed._ The beetles
were allowed to emerge and remain in the con—
tainer.

Cage 3. A 2" x 4" x 10” piece of American beech
infested with M. fasciatum was enclosed. As in
the above cage the adults were allowed to emerge
and remain in the container.

Containers with water bottles:

Cage l. A non—infested 2” x 4" x 9" piece of soft

maple was enclosed with ten adult beetles, M.

mali, previously taken from soft maple.

22
Cage 2. Two 2" x 4" x 9" pieces of soft maple in—
fested with M. 131111 were enclosed. The beetles
were allowed to emerge and remain in the con-
tainer.
Cage 3. Two 2" x 4" x 6" pieces of American
beech infested with M. fasciatum were enclosed.
The beetles were allowed to emerge and remain

in the cage .

When the moisture content of wood samples was desired
the following method of determination was used.

This method involves cutting of a small sample,
about 1/4 to 1/2 inch thick and the width of the board,
weighting and then drying in an oven (generally electrically
heated) at a constant temperature of 2120 to 2210 F. The
sample is re—weighed periodically until it reaches a con-
stant weight, which indicates that all the moisture has
been removed from it. The moisture content of the sam—
ple, expressed in percentage, is then determined by sub—
tracting the. last weight (oven dry) from the original (green)
weight, dividing the difference by the oven dry weight and

multiplying the result by 100.

 

 

 

 

Figure 2'. Lamp globe cage
with moist sand.

23

 

 

 

 

Figure 3. Lamp globe cage
with water bottles.

24

This Operation may be expressed as,

MC = [(w _ D) + D] x 100 (Panshin, 1949).

25

IV. PRESENTATION AND DISCUSSION OF DATA

Survey Of Insects from Sawmills
and Lumberyards

Collembola , springtails

 

Entomobrlidae. In both fall and spring many of these

 

insects were found between boards which had been piled with—
out an air space, thus causing moisture to form, giving the
springtails an ideal habitat. They are easily reCOgnized by
their ability to jump and the spring—like appendage on the un—
derside of the abdomen. The springtails feed primarily on
decayed vegetable matter or fungi. Therefore, they may be

considered slightly beneficial.

Thysanura , silve rfi sh

 

Lepismidae. They were found in the spring crawling ,

 

about wood which had been stacked inside sheds, lathe rooms,
and like places. The silvery scales covering the body and the
three long posterior appendages usually serve to distinguish

this group. They are chiefly nocturnal, feeding upon dry

27
vegetation, plant products, paste, or other articles having a
rather high starch content. About sawmills and lumber sheds

they are of little economic importance.

Corrodentia, booklice

 

Trogiidae. These insects were abundant in habitats

 

similar to those of the Silverfish. The members of the order
found were minute, Wingless forms; the heads and hind legs are
relatively large in prOportion to the rest of the body. While
they can cause great damage in granaries, libraries, and mu—
seums, they are of no importance in locations where lumber

is stored. Their diet consists mainly of vegetable and animal

debris, paste, fungi, and other organic substances.

ColeOptera, beetles

 

Cucujidae. Two species, Silvanus surinamensis and

 

_S_L. bidentatus, were found crawling about the surface Of boards

 

piled both in sheds and outdoors. The former, commonly
known as the sawtoothed grain beetle, is characterized by the
row Of marginal teeth on each side of the prothorax. It causes

considerable destruction to cereals, dried fruits, and seeds.

28

TABLE III

RESULTS OF SURVEY

 

 

Order and Family Locations Where Taken

Genus and Species
if of IInportance

 

Between Surface In the In the
Boards of Wood Sapwood Heartwood

 

Collembola
Entomobryidae —

Thysanura
Lepismi dae .. _

Cor rodentia
TrOgiidae _ ._

ColeOptera
- Cucujidae
Silvanus
surinamensis ..
Silvanus
bidentatus —
Lyctidae _
Lyctus Sp. _
Cerambycidae ' _ ..
Megacyllene
robiniae ..
Chrysomelidae —
Scolytidae
Monarthrum
fasciatum _ _
Monarthrum mali _ .. _
Xyleboris affinus —

 

 

 

 

 

 

HymenOptera
F ormicidae _
Camponotus sp . ._
Braconidae

 

 

 

29

_S__. bidentatus is usually taken from beneath bark, and probably

 

feeds on fungi. At first glance these insects resemble the
powder—post beetles. However, they may be distinguished
readily by the characteristics of their antennae. The last
three segments of the antennae Of the Cucujids are slightly
enlarged giving the appearance in most species of a three seg—

mented club, while the lyctids have only two segments enlarged.

Lyctidamjowder-post beetles. These beetles were

 

found in varied locations. NO infestations were observed on
inspection of the stocks of wholesale or retail lumber distrib-
utors. However, these lumberyards were inspected in late
fall and early spring, so it is possible that infestations may
have been present in lumber which had been on hand for a
short time but which could have contained dormant larvae
causing no characteristic dust.

In a lathe room Of one sawmill, a heavy infestation
was found in hickory material that had been allowed to stand
undisturbed for six or seven years.

Dead adult beetles were taken from the bases of the
pillars and joist Of a lumber storage shed. These structures

were covered with adult emergence holes, demonstrating that

30
the infestation had been present for many years. Such infesta—
tions. are reservoirs where pOpulations may build up, constitut—
ing a constant threat to any hardwood material stored in such
a building. When the beetles are established indoors, the life
cycle is shortened, causing the period of attack to be length—
ened.

Outdoors lyctids were found in air—seasoning hickory.
The area of infestation was limited to the boards just above
ground level.

The work of the lyctids is sometimes confused with
that Of termites. As described earlier, the adult powder-—
pOst beetles make small, round holes from the interior to the
surface Of the wood for emergence, and their galleries, run—
ning in all directions, are packed with powder. The termite
galleries usually run with the wood grain, are always void Of
refuse, and these insects do not push wood particles to the
outside (Bur. Ent. and P1. Quar., 1949). The surfaces Of
termite-infested wood never have the characteristic emergence
holes of the lyctids.

Infested wood collected in the fall contained only very

young larvae. WOOd from a partially heated structure examined

31
on April tenth contained much larger larvae than those from

the fall sample. NO pupae or adults were found.

Cerambycidae, long-horned wood borers. In the fall

 

survey many larvae of this family were taken from soft maple,

and in the spring several Megacyllene robiniae adults were

 

found in a mill yard.

The cerambycid beetles may be distinguished from other
beetles found in similar situations by their larger size and
very long antennae. The antennae are as long as the head and
thorax, and usually as long as or much longer than the body.

Primarily these insects feed in dead wood, but some of
the roundheaded borers cause reduction in grade Of lumber
because of serious damage resulting from attacks on recently
felled or living trees.’ Injury which is Often classed as powder-
post damage may result from the larval work of several spe—
cies of cerambycids. Some fOrms attack only recently cut
wood, but if the wood, after being attacked, is placed in build—
ings or stored in drier situations, the larval period is prolonged
for several years (Craighead, 1950). One species Hylotrupes
bajulus is an enemy of seasoned, dry, coniferous woods, Often

attacking rafters, joists, stacked dry lumber, and flooring.

32
The damage of the latter beetles may be distinguished from
lyctid injury by the larger size of the galleries and the coarse-

ness of the borings filling them.

Chrysomelidae, leaf beetles. Two species were taken

 

from the surface of piled lumber. Although anatomically sim-
ilar, they may be separated from the cerambycids by their
shorter antennae, seldom longer than the head and thorax, and
their smaller size. Beetles of this group are mostly leaf

feeders and of no importance about lumber. -

Scolytidae, Bark or timber beetles. In the fall the

 

adults Of three species of timber beetles were taken, two,

Monarthrum mali (Fitch) and Xyleborus affinis (Eich), from

 

soft maple, and Monarthrum fasciatum (Say) from American

 

beech. The habits and importance Of M. 213$. and M. fasciatum
have been discussed in the review Of literature.

No reference could be found of _)_(_. affinis having been
taken before in Michigan. Swaine (1918) stated that he had not
reCOgnized this species from Canada Or the northern states.
Blatchley and Leng (1916) and Leng (1920) record this insect

as having been taken in New Jersey and West Virginia.

33
Chamberlin (1949) stated that it is common along the Atlantic
coast from New Jersey. to Florida, and around the Gulf of
Mexico. Craighead (1950) reported that M. affinis was orig—
inally described from Cuba, and it breeds from New Jersey
southward to Florida and Mississippi.

Chamberlin (1949) lists as hosts of this beetle oak,
hickory, gum, and other hardwoods, and he stated that it
attacks logs and green lumber. Blatchley (1916) stated that
they succeed in establishing colonies only in the sapwood of
dying timber, but that they may be driven by hunger to attack
healthy trees. The damage from these attacks is of two types,
that from the construction of the burrows, and that Of causing
"blue stain. " The latter is caused from the introduction Of
fungus spores by the parent beetles. Discoloration results
from the penetration of the hyphae Of the fungi into the sap—
wood.

Five or six galleries are started, and an egg produced
in each, by a single female. The young, like those Of other
ambrosia beetles, feed on the fungus introduced by the female
(Blatchley, 1916). In a period of less than a month the eggs

can deveIOp into adults. Usually there is an unequal sex

34
distribution in favor of the females, this aiding in the prOpa—

gation of the species.

HymenOptera; bees, wasps, and ants

Formicidae, carpenter ants. Members of the genus

 

Camponotus were found in logs before milling and in the heart-

 

wood of seasoning lumber. They may attack the dead heart—
wood Of living trees, 10gs, house timbers, or almost any wood
materials. Their work is distinguished from powder—post in—
jury by galleries void Of powder and from termite damage by

the random method in which the galleries are made.

Braconidae. These minute to small parasitic wasps

 

were taken in large numbers from material infested with powder-
post beetles. The adults resemble small, winged, black ants.
Their larvae are believed to live as endOparasites of the im—
mature lyctid forms. Pupation takes place in a cocoon near

the surface of the wood. When present in large numbers, they
may greatly reduce a pOpulatiOn, but before they begin their

parasitism, a lyctid infestation is well established.

35

Miscellaneous

 

Polyporaceae, Fomes pini (Trametes pini), white spot.

 

This fungus, which causes white spotting Of wood, is commonly
thought to be the result Of insect damage. The disease Occurs

mostly on conifers, with the characteristic white spotting of

the wood varying with the Species of tree attacked (Von Schrenk,
1900). It may be distinguished from insect damage by the fact

that there is no dust or tunneling present.

Rearing of Lyctus Sp.

The results from the various methods used in the at—

tempted prOpagation Of lyctids are as follows:

Glass lamp globe type cagg. From these cages fifteen
powder—post beetles emerged. -Thirteen of these were from
the two cages kept in the constant temperature room. The
other two emerged from the sample held at room temperature.
Many environmental factors could have acted upon the larvae,
but the most probable factor causing the low emergence rate
was the heavy parasitism. From these three cages a total Of

81 hyrnenOpterouS parasites were taken.

36

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750 ml. jar with cloth covgr. Six adult beetles emerged

 

within one month after enclosure of the infested chips. No para-
sites were taken. The small number Of beetles obtained from
this container may be due to injury of some larvae in cutting

the chips or to the fact that only a few larvae were present,

as the sample was small.

The six beetles were all considerably smaller in size
than those emerging from the larger pieces of wood. The
chips used were taken from the hickory samples in the lamp
globe cages, making the diet Of the two groups approximately
the same. From this it may be assumed that possibly the
growth of these six beetles was retarded by the difference in
the external environment of the chips._ The temperature (240
C.) at which the wood samples were kept would cause more

rapid reduction Of moisture content in the small pieces.

750 ml. jar with glass cover. Three weeks after the
chips were enclosed, mold was noted. NO adults or parasites

were taken from this jar.

Large battery jar; water; hickory. Results similar to

those from the small glass covered container were obtained.

38
Within a month mold was formed, and soon afterwards it was
noted that the production of powder had ceased; No adults or
parasites were taken. On examination of the galleries, they
were found to have mold running through them. The moisture
content Of a sample from the same piece used in this jar, but
that had been kept at room temperature, was 9.1 percent.
After two months and twenty—six days the moisture content
of the enclosed sample had raised to 22.8 percent. The beetles
seldom attack wood with a moisture content greater than 15

percent.

Lalge battery jar; water; black ash. NO mold was noted

 

on the enclosed wood until late June. On July eighteenth only
a small amount was present, all of this protruding from the

eme rgence hole 3 .

Largibatteryfir; salts; hickory. The results here
were identical to those obtained in the large battery jar con—
taining hickory with water. The moisture content of this sam—

ple after enclosure raised to 19.3 percent.

39

Although it was impossible to conduct the experiment
as planned because large numbers of adults were unobtainable,
some conclusions may be drawn from the work.

There would be little direct effect of changes in humid—
ity on the develOpment of organisms enclosed within a block of
wood. It seems that the relative humidity of an environment
would have to remain constant long enough to change the mois—
ture content of the wood before it would affect the organism.
Humidity would undoubtedly have the greatest effect on devel—
Opment of the egg, either lengthening or shortening the period
between oviposition and hatching, or making them non—viable.
'It may also be a factor in the length of pupation, since this
takes place near the surface.

Infestation Experiments with Monarthrum mali
(Fitch) and M. fasciatum (Say)

 

From Table V, it can be seen that only one of the Spe—
cies tested, M. mali, made an attempt to establish new burrows
in the partially seasoned samples. The results from the indi—

vidual cages are as follows.

TABLE V

DATA FROM SCOLYTID EXPERIMENT

40

 

 

 

 

Sam- Num-
ple ber Number Date Date
and of
. of Emer— En—
Containers Bee— Bee-
t1 t1 Beetles gence trance
es es Emerged Began Noted
En— En—
closed closed
With Sand
Cage 1
M. mali Oct. 18 10 - — Oct. 29
Cage 2
M. mali Oct. 18 - 8 Oct. 20 Oct. 29
Cage 3
M. fasciatum Oct. 18 - 0 — .-
With Water
Cage l
M. mali Oct. 18 10 — - —
Cage 2
M. mali Oct. 18 — 0 — —
Cage 3

M. fasciatum Oct. 18 — 6 Oct. 21

 

 

41

Containers with moist sand:

Cage 1.

One burrow was begun on the bottom Of the
sample Of wood, the surface nearest the moisture.
Two adults appeared to be working together at
beginning the burrow. The other beetles in the
cage simply crawled about On the wood, and
within two weeks all appeared dead except those
in the new burrow from which fresh dust was
being pushed. After four weeks of enclosure the
dust production ceased, probably indicating that
the enclosed beetles could not survive as the
moisture content Of the wood was lowered. The
moisture content Of the sample after enclosure
at 240 C. was 10.3 percent, while that of a
sample from the same stock kept at room tem—
perature was 14.2 percent, a loss of 3.9 percent
during the time of the experiment. This loss
could possibly have brought the moisture content
below the threshold Of the beetles.

On examination of the burrow, it was found

to be 1.9 cm. long, with no dead adults inside.

Cage 2.

Cage 3.

42
Because Of the small number Of beetles used and
the fact that they were selected without examina—
tion for sex, the sex ratio may not have been
even. Since this species is reported to be mo-
nogamous, other burrows may not have been
started because of a lack of mates.

Eight adult beetles emerged about the
twentieth of October. Most of them died within
a few days. New boring dust Showed where one
beetle had attempted to enter. When the wood
was cut Open for inspection the new burrow was
found to be 4.5 m1. long. Many dead adults were
found in the old galleries.

The new entrance hole was formed in the
center Of a patch of fungus on the bottom surface
of the wood just above the moist sand.

Nothing emerged in. this cage. When the
wood was examined many dead adults were found

in the niches where the eggs had been placed.

43
Containers with water:

Cage 1. For the first few days after the insects
were enclosed, they crawled actively about, but
after approximately three weeks all were dead.

Cage 2. NO scolytids emerged in this cage. Dead
adults were recovered from the galleries when
the sample was cut Open and examined.

Cage 3. Six adults emerged about the twenty—first
Of October; after crawling about the surface Of
the wood for a few days all died.

Although this experiment was not carried out under the
conditions present in mill yards, it is evident that the adults
of M. Mali will attack partially seasoned lumber in Michigan,
and that under more favorable conditions M. fasciatum may

still be a threat to seasoning lumber.

V. SUMMARY AND CONCLUSIONS

During the fall of 1950 two problems were undertaken:
(l) a survey of insects infesting seasoning lumber, and (2) the
effects of different humidities on lyctid powder-post beetles.

Early in the survey much lumber was found damaged
by scolytid beetles; Because Of this a third problem was in—
vestigated, i.e. , the possible re—infestation Of partially seasoned
lumber by mature ambrosia beetles.

Of the insects collected, those causing a reduction in
grade to lumber were members of the following families:
Lyctidae, Cerambycidae, Scolytidae, and Formicidae. The
most important pests to seasoned or seasoning lumber were
the lyctids. The other three families appeared to cause their
greatest damage before the 10gs reach the sawmills.

One species Of Scolytidae, Xyleboris affinis, was taken

 

from soft maple. NO record could be found of this insect
having been taken before in Michigan.
Attempts at rearing lyctids did not produce a sufficient

number of beetles for the planned investigations. Heavy

 

45
parasitism by a minute braconid wasp was thought to be the
reason for the low number emerging.

Several types Of containers were tried for rearing lyc—
tids. From the results it is impossible to state which was
the most satisfactory. Cutting infested wood into small pieces,
instead of introducing large ones, showed the greatest possibil—
ities.

When lyctid infested wood was placed in small closed
containers at high humidities, the wood samples took on much
moisture. This brought the moisture content Of the wood above
that which lyctid beetles could survive, and made conditions
advantageous for mold formation. It has been reported that
powder—post beetles seldom attack wood with a moisture con-
tent above fifteen percent. The high humidities used in the
experiment caused the moisture content to rise above twenty
percent.

It seems possible to make the assumption from the re-
sults, that slight variation of air humidity, such as occurs in
nature, would have little effect on lyctid forms. To display

marked effects on develOpment, a given percentage of relative

46
humidity would have to remain constant long enough to alter
the moisture content of the infested wood.

In two instances Monarthrum mali re—entered partially

 

seasoned wood samples. M. fasciatum did not enter but may

 

be capable of doing so under more suitable conditions. It ap—
pears possible tO predict that whenever infestations Of M. mali

or M. fasciatum are present undamaged lumber is in danger Of

 

attack.

LITERATURE CITED

Anonymous
1939 Chemical Dip Tests Against Lyctus Powder Post
Beetles, Lyctus paralleIOpipedus (Melsh.) and Lyctus
planicollis (Le Conte). Southern Lumberman 159
(2009»105_109.

 

Blatchley, W. S.
1910 ColeOptera Of Indiana. Nature Publishing CO., Indi-

anapoli S , Ind.

, and C. W. Leng
1916 RhynchOphora or Weevils of North Eastern America.
Nature Publishing Co. I Indianapolis, Ind.

Bureau of Entomology and Plant Quarantine
1949 Preventing Damage to Buildings by Subterranean
Termites and their Control. USDA Farm. Bul.
NO. 1911.

Buxton, P. A., and K. Mellanby
1934 The Measurement and Control of Humidity. Bull.
Ent. Res. 25:171—177.

Chamberlin, W. J.
1949 Insects Affecting Forest Products and Other- Materials.

Published by the author at Oregon State College,
Corvallis, Oregon.

Christian, M. B.
1939 Experiments on the Prevention Of Ambrosia Beetle
Damage in Hardwoods. Southern Lumberman 159

(2009k110—112.

 

1940 Lyctus Beetle Damage Prevention. Southern Lumber-
man l60(2021):47-—49.

48

Comstock, J. H.
1948 An Introduction to Entomology. 9th ed. ComstOck
Publishing CO., Ithaca, N. Y.

Craighead, F. C.
1950 Insect Enemies Of Eastern Forests. USDA Misc.

Pub. NO. 657.

Doane, R. W.., E. C. Van Dyke, W. J. Chamberlin, and
1936 H. E. Burke. Forest Insects. McGraw—Hill, N. Y.

Essig, E. ‘O..
1942 College Entomology. Macmillan CO. , New York.

Fall, C. H.
1905 Revision of the Ptinidae of Boreal America. Trans.

Amer. Ent. Soc. 31:97-297.

Fisher, R. C.
1940 Beetles Injurious tO Timber and Furniture. Forest
Products Research Bul., No. 19, London.

Graham, 5. A.
1929 Principles of Forest Entomology. McGraw—Hill, N. Y.

Handbook of Chemistry and Physics
1949 3lst ed. Chemical Rubber CO., Cleveland.

Hansens, E. J.
1944 Humidity in Relation to the Ovicidal Effects Of Pow—
ders Used Against the Body Louse. Jour. of Econ.
Ent. 37:750—755.

Le Conte, J. L., and G. H. Horn
1883 Classification of the ColeOptera Of North America.
Smithsonian Misc. C011. No. 507. Vol. 26:1-567.

Leng, C.' W.
1920 Catalogue Of the ColeOptera of America, North Of
Mexico. John D. Sherman, Jr., Mount Vernon, N. Y.

49

Mallis, A.
1945 Handbook of Pest Control. MacNair—Dorland CO. .
N. Y.

Martin, E. C.
1939 The HygrOSCOpic PrOperties of Honey. Jour. Econ.

Ent. 32(5):ooo_oo3.

Panshin, A. J.
1949 Lumber Dry Kilns and Their Operations. Mich. State
Col., Agr. Exp. Sta. Spec. Bul. 359.

Peterson, A.
1934 A Manual of EntomolOgical Equipment and Methods.
Published by the author at Ohio State Univ., Columbus,

Ohio.

Snyder, T. E.

1924 Determination Of Temperatures Fatal to the Powder-
post Beetle Lyctus planicollus (Le Conte), by Steam-
ing Infested Ash and Oak Lumber in a Kiln. Jour.
Agr. Res. 28:1033-1038.

 

Snyder, T. E.
1927 Defects in Timber Caused by Insects. USDA Bul.

1490, p. 46.

 

1938 Preventing Damage by Lyctus Powder—Post Beetles.
USDA Farm. Bul. NO. 1477.

Swaine, J. M.
1918 Canadian Bark—beetles. Dom. of Can. Dept. Agri. Ent.

Br. Bul. 14, part 11.

Wilson, R. E.
1921 Humidity Control by Means of Sulphuric Acid Solutions

with Critical Compilation of Vapor Pressure Data.
Jour. Ind. and Chem. Eng. 13:326—31.

Von Schrenk, H.
1900 Fungous Diseases of Forest Trees. Yearbook USDA

pp. 199—210.

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