PROCEEDINGS OF THE 



ENTOMOLOGICAL SOCIETY OF WASHINGTON 



VOL. 20 OCTOBER, 1918 No. 7 



THREE HUNDRED AND FIFTEENTH MEETING OCTOBER 2, 1918. 



NOTES ON THE COCOON SPINNING HABITS OF TWO SPECIES 



OF BRACONIDS (HYM.). 



BY R. A. CUSHMAN, 

 Bureau of Entomology. 



The cocoon spinning habits of insects have been for a long 

 time of greatest interest to me, especially of those that construct 

 their cocoons 'under apparently difficult conditions, such as 

 Apanteles congregatus Say, the cocoons of which stand on end on 

 the surface of the parasitized caterpillar, and Meteorus hyphan- 

 triae Riley, which suspends its cocoon at the end of a long strand 

 of silk. It was with great pleasure, therefore, that I watched 

 both of the above named species spin their coccoons during the 

 past summer. 



Apanteles congregatus Say. 



On June 20th I secured a larva of the catalpa sphinx (Cerato- 

 mia catalpae Boisd.), which bore on its back a single cocoon of 

 Apanteles. Other parasite larvae very shortly began to emerge 

 from the host. Placing the caterpillar under my binocular micro- 

 scope I watched the entire operation from emergence to the 

 completion of the cocoon to the point where it becomes too 

 opaque to see through. 



In emerging from the host the parasite larva first clears away 

 with its mandibles the muscle tissue from a small area under 

 the integrement, moving its head about until the inner surface is 

 entirely clean. Then by repeated back and forth motion of the 

 head with the mandibles projecting it gradually wears a rupture 

 in the skin, through which it slowly issues by a peristaltic-like 

 motion. At this time the larva can be seen to swallow large 

 bubbles of air. When from a fourth to a third of its body is 

 free the skin of the parasite ruptures just back of the head, the 

 hole rapidly enlarging to permit the body of the larva to pass 

 through. That portion of the cxuvium that covers the face 



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