PROC. ENT. SOC. WASH., VOL. 20, NO. 7, OCT., 1918 135 



with a coarse outer network of strands. At the upper end of 

 the cocoon the suspending strand forms a coil of several turns. 

 This little coil is the clever feature of the cocoon and holds the 

 secret of its construction. 



At one time during the past summer I had a number of colonies 

 of the fall webworm (Hyphantria cunea Drury) that had been 

 exposed to the attack of Meteorus hyphantriae, and from which 

 I had already secured a few cocoons. I examined a large number 

 of these caterpillars in the hope of rinding a parasite larva in the 

 act of emergence and finally found one that had a slight swelling 

 on one side near the caudal end. Examination of this showed 

 that the swelling was caused by the pressure of the parasite larva 

 that was about to issue from within the body of the caterpillar. 

 It had cleared away all the soft tissue at that point, and its face 

 could be distinctly seen through the integument of the host. 

 In this condition it remained for two hours or more, during which 

 time I placed the caterpillar in a phial and carried it home with 

 me. It was nearly dark when the parasite finally issued. Before 

 entirely emerging from its host the larva reached over with its 

 head and fastened the end of its thread to the cotton plug of the 

 phial. It then released its hold on the host and swung down at 

 the end of the strand, hanging head up. It now curled up the body 

 and twisted the silk about its caudal end, grasping it in the deep 

 constriction between the last two segments and then straightened 

 out, thus lengthening the strand. It repeated this operation 

 several times until the thread was about an inch long. Taking a 

 new hold on the strand it proceeded to wind it several times 

 about its caudal end, thus forming the coil referred to. With 

 the support thus formed and hanging head downward it began 

 the construction of the outer loose-meshed layer of the cocoon by 

 alternately straightening out its body, thus pulling out the 

 silk, and curling up to fasten the end to the loops already formed. 

 After making a few courses of these loops it released its hold 

 on the coil about the last segment and thereafter held to the 

 meshes by the short, finger-like cauda. At the beginning, when 

 most of its body was not yet enclosed, it worked from the outside, 

 fastening the ends of the loops on the outside of those above; 

 but as the work progressed to a point where the body was mostly 

 enclosed it worked entirely from the inside. When finished this 

 meshed outer layer still had a hole at the lower end correspond- 

 ing in size to the emergence hole of the adult. The outer struc- 

 ture completed,, the larva proceeded to the building of the inner 

 layer. 



At this point darkness prevented further observations, but a 

 few days later another larva was caught just after it had started 

 its cocoon, and the construction of the inner layer was watched. 



