A laboratory method for the study of insects in their cocoons

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Title:
A laboratory method for the study of insects in their cocoons
Physical Description:
Mixed Material
Creator:
Fife, L. Courtney
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030345466
oclc - 781636411
System ID:
AA00017458:00001


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ET-155 Feb.;uary 1940

United States Department of Agriculture
Bureau of Entomology and Plant Quarantine


A LABORATORY METHOD FOR THE ZfUDY OF INSECTS IN THEIR COCOONS

By L. Courtney Fife,
Division of Cot4oon I'sect Investigationsi



In m.;y studies of insert4 it is essential to make daily ob-
servatinnq on the development of larvae and pupae in their cocoons
without disturbing them. A cocooning roc!. for this purpose was
devised by E. R, Van Leeuwen, 1 and later a similar rack was devised
by Rodney Cecil.2 However, these racks are rather large and could
not be used in desiccators for studying the effect of humidity on
larvae and pupae of the pink boll'.v.orm (Pectinojph2or, gopssyp la
(Saund.)) ii, their cocoons. The method devised to overcome this
difficulty may be useful to other workers in the study of insects
that spin cocoons during their development.

Method and Procedure

As shown in figure 1, larvae are permitted to spin up between
the bottom surface of a petri dish and a thin disc of absorbent
cotton. This cotton disc can be easily made by stripping a thin
layer from a roll of absorbent cotton obtained in a drug store.
A disc of toilet tissue is placed over the cotton disc. These
discs are cut to fit the inner surface of the dish.

From 30 to 50 larvae are placed in the dish and given a few
shakes to distribute them somewhat evenly over the surface. Thp
disc of absorbent cotton is quickly placed over the larvae, and -hen
the disc of toilet tissue is placed over the cotton disc. A heavy
cardboard disc is placed over the other tw.o discs, and a light
weight is placed on top. The cardboard and weight act as a thig-
motropic stimulus to the larvae in spinning their cocoons. Soon
after the larvae start to spin their cocoons, the weight and disc
of cardboard are removed.


SSiegler, E. H., and Plank, H. K. Life history of the
codling moth in the Grand Valley of Colorado. U. S. Dept. Agr.
Bull. 932, 119 pp. Sept. 1921.

a Cecil, Rodney. A cocooning, rack. Bur. Ent. and PI. Quar.,
ET-94 (multigraphed). March 1937.






2 -

In the studies made by the writer very few larvae left their
cocoons when exposed to various high or low temperatures or a wide
range in humidity.

If individual records are desired, each insect can be num-
bered by the use of India ink on the outside bottom surface of the
petri dish. A tight-fitting lid of copper screen can be substituted
for the glass cover of the petri dish, if desired.

From figure 1 it will be noted that the various stages of
the insect can be easily recognized without disturbing them when
the dish is held up to the light.









































Figure 1.--Spin-ups of the pink bollworm between the bottom
surface of a petri dish and a thin disc of absorbent cotton.




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