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Thesis.

Some Coccidas of the Green House,

. ABE /

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Clara M. Steele.

Class '98.
 

THES!

2.2.
384
THS
‘

Some Green House Coccidae,

In considering subjects for a thesis there seemed to be nothing
more worthy to be worked up than that of the Coccidae of the green house.
TMese insects. if not well understood and properly cared for, make life
Miserable for the florist who is trying to keep his plants free from
pests. The ease with which they are carried from one place to another,
and the rapidity with which they multiply make them very difficult to
keep in cheok. For some of them proper and efficient remedies are diffi-
cult to find. When once they get a good start, there is scarcely any
hope of keeping them in check, and if they become very numerous, they
will destroy the plants. |

These insects are not only of economic importance in conservatories
but are of immense importance in orchards. Perhaps there is no pest
which is more difficult to control. and which is now attracting more
attention than the San Jose scale.

It is to some of the species found in the Michigan Agricultural
College green house. however, that we have directed our attention. An
attempt was made to differentiate the Coccidae by the character of the
scales alone. But the determination of the species was made by use of
the microscopic characters.

It is interesting. and indeed, necessary to know the position
these insects have in nature before we make a study of them.

The sub-families Diaspinae to which belong the true scale insects
Lecaninae to which belong the lecaniums. and others, and the Coccinae

to which the mealy bugs and others belong are the three principal
L088 65
WN

Il.

sub-families of the family Coccidae.

The Coccidase constitute a family belonging to the group Homoptera
of the order Hemiptera.

Interesting and valuable as it undoubtedly would have been to have
worked out the life history of these troublesome insects, we decided
at the outset of this work that owing to the limited amount of time, it
would be wiser to omit all such experiments. For this reason we quote
priefly from other works on the subject.

The newly hatched scale insect is oval in outline much flattened,
with six legs, a pair of antennae, and an apparatus for sucking the
juices from plants. After wandering about for a few hours, the young
scale insect settles on some part of the plant and inserts its beak,
and drawing its nourishment from the plant begins its growth. After a
short time there appears over its body a slight covering of waxy or
cottony material which serves both for protection and concealment. Soon
afterward the larva commences to secrete a rirm papery shieldlike
covering which afterward becomes the permanent scale. During the comple-
tion of this scale tho skin is shed once by the male and twice by the
female. Both sexes lose their legs and antennae in shedding the skin
thus becoming mere immovable scales capable only of feeding and secreting
the scrle.

After a time the insect molts a second time “nd changes to the
pupa stage during which time the wings, legs. antennae and other appen~
dages are formed inside the pupa sxin. Before long the male emerges as
a delicate two winged insect with one or two long, tail like appendages.
As its life is vory short thus requiring no food the adult male has no
mouth parts well developed, and the two pairs of eyes take their place.
Me female always remains under the scale. After union of the two sexes

the male dies and the female commences to lay her eggs, retiring tnto
Iil.
one end of the soale and gradually shrinking during the process to a
mere shriveled skin. The time when the eggs are laid varies in different
species, many laying them during the autum, but some remaining in a
partly grown condition during the winter, deposit them in the spring.
In order that we may study the Coccidae to eny advantage, we must
have some method of classifying them. In classifying the sub-family

Diaspinas we generally use the charactersof the scales and not those of

 

the insects. The form of the scales, the position of the exnviae, are

the ones most used. The difference in form and color between soales of
the different sexes is important. The presence or absence of the central
carina and the cpmpatative size of the exuviae are also important charac-
ters.

When the female scaie is circular, or nearly so, with the exuviae
more or less nearly marginal or central and the male scale is similiar,
the insects are of the genus Aspidiotus.

When the female scale is circular with the exuviae in same posit-
ion as other and the male scale elongated with exuviae at one end, the
insect may belong to either of two genera: If the male scale is white
with a central carina the insect is a member of genus Diaspis;

If the male scale is not white and with no central carina the gems
is Parlatoria. |

On the other hand, if the female scale is elongated with the
exuviae at one end and the exuviae are small, the male scale being white

and carinated. we have the genus Chionaspis.

 

If the male scale is white but not carinated we have the genus
Poliaspis.
If the male scale is similiar in form to the female scale we have

genus Mytilaspis.

 

If the exuviae are large and two molted skins visible on female
 

cn

soale, the genus is Parlatoria.

If the exuvia are large and second skin is covered with a secretion
we have Uhleria. |

Following we give a description of each of the species found and
studied:

Ischnaspis fildformis
(Plate I A. I and 2)

This is in this latitude, a green house scale. It is not widely
distributed but when found is very troublesome. It was introduced into
this country from Europe. Scale of the female is long, narrow, almost
the same width throughout though slightly narrowed at the anterior end.
The exuviae is small and at one end of the scale. It has a rather promi-
nent ridge running lengthwise and has seversl small cross lines. The
exuviae varies in color from light brown to dark brown whtle the remain-
der of the scale is black. sometimes with a very narrow and delicate
margin of white or lirhter brown. The veutral scale is well developed;
It is greyish white in color and is attached at ths sides. Scale of male
is about one third the length of the female scale and is also straight
and narrow. It is usually the same color as the female scale although
sometimes it varies from a light brown to black. On the scales of both
sexes fine lines are found indicating different stages of growth. The
edges of both scales are even and clean out and not irregular. This
speoies is quite abundant here and is found especially on the Date Palm.

Mytilaspis citricola (Packard)
(Plate I B. I and 2)

The female scale is light brown in color. very narrow anteriorly
but greatly developed at the posterior end. The edges are curved and
“ivregular. The exuviae are small in size and about game color as the

rest of the scale. It has the ridge running lengthwise with the minute
oross lines as in Ischnaspis filioformis. The veutral scale is present
well developed, white in color. Sometimes it is thinly developed in the
center of the posterior end. The female scale has a thin delicate margin
of white also. The shape of these scales vary greatly owing to the
different positions on the leaf or stem. The male scale is about one
half the length of the female scale but is very different in shape.
Instead of being much larger at the posterior end it is nearly liniar
very slightly enlarged at the posterior end. The male scale resembles
the female in color and the exuviae are very similiar. Both mle and
female scales show the fine lines indicating growth. This species is a
very troublesome one to the orange growers in Florida and elsewhere.
It is very abundant, being found mostly on Citrus auriantica in our
conservatory.
Aspidiotus ficus (Riley MSS)
(Plate II A. I and 2)

This species is the most abundant of any found in the green house.
It will grow on nearly all plants and is very troublesome indeed. The
female scale is circular or very nearly so, with the exuviae more or
less central. The main part of the scale is black. It has, however, a
margin of white. This margin varies in width in different stages of
growth being narrowest when the insect is adult. The position of the
first skin is shown by a slight prominence, the skin when fresh is white
The second skin is brick red sometimes, covered with a thin film of
white. The scales vary in size but the largest are about one-eighth of
an inch in diameter. The male soale is about one-fourth the size of the
femaldscale and often has a thin flap developed from one side, which is
white or pale green in color. Otherwise, the scale resembles that of the

female. This species has a long host plant list. being found on the
 

 

following plants in our green house:

I. Aralia sieboldi 5. Raphis flabelli formis
2. Areca paneria 6. Areca rubra

3. Kentia fosteriana 7. Cycas revoluta

4. Kentia belmoriana 8. Cypripedium insigne

9. Coelogyne cristata
Aspidiotw’s nerii Bouche’.

(Plate II B. I and 2) +

The female scale is quite iFregular in shape, varying from ocir-

cular to nearly rectangular in some cases. The position occupied on
the leaf has much to do with this. The first skin which is small, makes
@ slight prominence and the second skin which is larger and is muoh
darker, has the appearance of surrounding the first one. The scale has
&@ thinner margin around the edge which varies in width. The veutral
scale is not well developed. The male scale is similiar but is very
much smaller in size. Its outline is very irregular. having the thinner
margin also. The texture and color of the male and female scales are
alike. This species is not as abundant as A. ficus. It is found on two
plants in our conservatory, Chamaerops prascox and Corypha australis.

Aspidiotus ancylus, Putnam.
(Plate III B. I and 2)

This scale was found quite rarely in the conservatory here, being
found on Hypericum and on Evonymus only. It is quite abundant in open
air however, having there a large host pinnt list. The female scale is
rather irregular in shape, resembling A. nerii in this respect. It is
usually wider than long with the exuviae sligntly lateral of the center.
The exuviae are covered with a thin film of white which oan be easily
removed leaving the exuviae, which are brick red in color, exposed. The

remainder of the scale, which is white, is grey in color, sometimes,

however, it is nearly black. The veutral scale is present. being very
VII.
thin and delicate. The male scale is similiar to the female scale, but
is much smaller and slightly more elongate.

Diaspis cacti Comstock

 

(Plate III A. I and 2)

This scale which is very injurious, takes its specific name from
the host plant. It is found on nearly all cacti. The male scale is long,
glender, white and unincarinated. The exuviae vary in color from pale
yellow to brown, while the remainder of the scale is white, tius making
a very striking appearance. The outline is quite regular, being nearly
straight. The female scale varies from white to pale green in color
with the exuviae of a dark color, varying from yellow to dark brown.

The female scales of the genus Diaspis, are ciroular with the exuviae

more or less central, while the male scales are long, white. and carinated
with the exuviae at one end. While in the genus ChioRaspis, the female
scales are also long with the exuviae at one end. The female scale of
Diaspis cacti is somewhat larger than most circular scales.

Chionaspis evuonymi Comstock,

 

(Plate IV A. I and 2)

The female scale is a dull brown in color. The scale, like all
those in this genus, is long with the exuviae at one extremity. In this
species, the first skin is yellow in color, the second is darker. nearly
as dark as the rest of the scale. The anterior end is narrow, but near
the center of the second skin, the scale begins to widen very much, and
is three or four times as wide at the posterior end as at the anterior
end. It has quite a regular margin. The scales differ much in shape
owing to the different positions occupied on the plant. Some of the
scales are straight and some more or less gently curved. The veutral scale
is well developed being joined to the dorsal scale at the sides, but

free at the posterior extremity. The male scale is long, with parallel
 

VIII.
sides, white and tricarinated. The exuviae is pale yellow. The outline
of these scales is quite regular. and they do not vary much in shape.
This species takes its specific name from its host Enouynius.
Chionaspis aspidistrae Signoret
(Plate IV B. I and 2)

Tis scale is found on ferns in our conservatory. The female scale
varies from clear yellow to brown in color and is rather regular in
outline. The exuviae is small, of the same color as the other part of
the scale. The first skin is of the normal size but the second skin is
larger and has quite a prominent ridge, which is absent in the species

euonymi belonging to the same genus. The female scale. instead of being
straignt or gently curved as in euonymi, is very abruptly curved in
most of the specimens examined. The female scale is slightly smaller in
this speoies than in euonymi. The male scale is white and ocarinated as
in the other species. The outline of male scale of aspidistrae is mich
more irregular than that of suonymi. In some species it is very irregular
more so than the male socales of any other species studied. This speoies
is found mainly on Pteris serrulsta cristata but it is also found on
Cycas revoluta.

The sub-family Lecaninas is classified as follows:

 

A. Body naked or nearly so.
I. Female secreting a mass of cottony material in which the

ergs are laid---------- Pulvinaria

 

2. Female not secreting a cottony material. and laying her

eges peneath her body ---------- Lecanium

 

B. Body covered with a layer of wax.---------~- Ceroplastes

 

The genus Lecanium is the only one studied. We found, we believe,

 

three species. two which we determined and one which we could not.
1O

Lecanium tesellatum (Signoret )

 

(Plate V. B.)(Plate VII, 1.2 $.and 4)

This lecanium is flat, much longer than broad, and usually narrowed
anteriorly. Somtimes the shape which is usually oval, is much varied
owing to different positions on the leaves. The color is usually a
chestnut brown but is lighter along the margin. The surface is distinctly
reticulated. Under the microscope the surface appears to be covered
with quadrilateral figures which are connected with transparent lines.
These figures become longer nearer the edge and the lines wider. When
seen under a higher power, the legs antennae, the anal plates and the
mout!: parts can be plainly seen. The antennae are eight jointed and vary
in length as follows: The first is rather short, the second is much
longer, the third is longer than the second. the fourth is slightly
longer than the first hyxt shorter than the second, the fifth is same
length as second, the sixth is same as fourth, the seventh is shorter
than first and the eighth is about the same length as the third but is
mich narrower and is notched in three places on each side. The legs are
four jointed, having three digitules arising from the base of the tarsal
Claw. Two of them are long. slender and pointed. The other one is stout
with a knob on the end. This species is found on Latania also very
abundantly on Dactyllifera. the Date Palm.

Lecanium hemisphaegricum ( Targioni-Tozzetti )
(Plate V. A.)(Plate VI.I, 2 and 3)

This species is very abundant on the Sago Palm (Cycas revoluta)
and is also found on Pteris serrulata, The specific name was suggested
by its form. This is hemisphaerical with a flattened margin. The lon-
gitudinal carina is sometimes very prominent but more often is rather
obscure or entirely wanting except at the ends of the body. The trans-—
verse carinae are usually present and quite prominent when the longi-

tudinal carina is prominent, but when it is indistinct, they are usually
wanting. When under the microscope. the surface is ssen to be covered
with numerous pits, usually circular or elliptical but sometimes oval
and quite large. The antennae are eight jointed and the joints vary in
length as follows: The first is rather short, the second is a little
shorter, the third is longest, the fourth is slightly shorter then the
‘thira,: the fifth is about the same length as second, the sixth is
shorter then the second, the seventh is shorter then sixth and the
eighth is next as long as the third, being narrow with three notches on
each side opposite each other. The legs are four jointed, having four
digitules arising near the base of the tarsal claw, two long slender
ones knobbed and two rather short, stout ones having a larre knob on
the ends. This species varies in color from a chestnut brown to a seal
brown.

Lecanium species(?)

 

(Plate VIII)( Plate IX.I.2.and 3)
We found on Pittosporium tobira a lecanium which is quito different
‘from the other two species found in our conservatory. It is very muoh
smaller in size and lighter in color, being nearly tan in some specimens
and varying to chestnut brown.The longitudinal carina is present and
quite distinct. The transverse carinae are always well developed, tmis
 @aiffering from hemispnaericum in this respect. Ths scale is nearly as
wide as long and is flatter than hemisphaericum. The antennae are eight
jointed. The first is short. the second is slightly longer. the third
longest the fourth longer than second but shorter than third, the fifth
is about the same as first. the sixth is slightly longer than fifth,
the seventh is shortest, the eighth is shorter than third, narrow with
the edges three notched on each side opposite each other. The leg in
this species has three digitules, two short, stout ones with large knobs

and one long.slender one with a small knob.
Second Report of the Cornell University Experiment Station, I882-3.
Agrioultural Report of the Entomologist for 1880.

List of Works Consulted During the Fore-going Study.

Comstock's Manual of Insects.

Comstock's Introduction to Entomology.

Report of Agricultural Experiment Station of University of

California for 1894-6.

Essai sur les Cochenilles, Par M. le docteur V. Signoret.

First Annual Report of State Entomologist of Minnesota for 1895.

Il.

IIt.

VIII.
IX.

Explanation of Plates.

Ischnaspis filoformis I.

e

 

Mytilaspis citricola

 

Aspidiotus ficus

 

Aspidiotus nerii

 

Aspidiotus ancylus

 

Chionaspis euonymi

 

I
I.
I.
Diaspis cacti I.
I.
I.
I.

. Chionaspis aspidistrae

 

Lecanium hemisphaericum

 

Gr oe DP oD PP oe

Lecanium tesselatum

 

Female
Female
Female
Female
Female
Female
Female

Fenale

Details of Lecanium hemisphaericum

 

I. Antenna. 2. Leg. 3. Anal Plates.

Details of Lecanium tesselatum

 

I. Antenna. 2. Leg. 3. Anal plates. 4. Insect mich enlarged,

showing tesselations.

Lecanium species?

 

Detail of Lecanium species?

I. Antenna. 2, Leg. 3. Anal plates.

scale,
scale,
scale,
scale,
soale.
scale,
scale,

scale,

Male
Male
Male

. Male

Male

. Male

Male

. Male

scale.
scale.
scale,
scale.
scale.
scale.
scale.

scale,
Table Showing Difference Between the Three Species

of Lecaniums Studied.

 

 

 

 

 

Species L. Tesselstum L. Hemisphericum Species(?)

Size 4 x 3,1/2 m.m. 3.x 3, 1/2 m.m. 2,1/2 x 2mm.

Color Chestnut brown Varies from light Varies from tan to
brown to nearly chestnut brown.
black.

Form Very flat. sometimegVery convex,slight- |Somewhat convex,

convex.

ly emarginate.

emarginate.

 

Skin Texture

Tesselate

Evenly punctuate.
Rather oval.

Punctuate around
edges, not in
center.

 

Slightly reticulate,

 

 

Surface Dull, evenly sprink~Carinated medially
led with very fine {dull, evenly sprink-
points. led with fine
Sometimes carinatedjpoints.
T.longitudinal
2.transverse.

Antennae

Number of

joints in 3-8-2-5-8-4-2-1-7 3-8-4-I-5~-2-7 3-8~2-4-6-5-I-7

order of

size.

Legs | I Club shaped. 2 Club shaped ones |2@ club shaped ones

digitules digituls knobbed. Knobbed. knobbed.

 

2 long narrow ones
pointed.

2 long,slender ones
obbed.

 

I long, slender
one knobbed.

 

 

 
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