The Chalcis Flies 



appearance. Usually their growth is uniform. A retardation in 

 the development of individuals in the group results in death. 

 When full grown they turn white and relax their hold. 



The poor caterpillar, which up to this time has shown no signs 

 of being affected, except by its sickly yellowish color and by its 

 very slow growth, collapses and dies as soon as a single one of the 

 parasitic larvae withdraws, and the same fate overtakes those 

 parasitic maggots which are at the time less advanced in their 

 development. If one of the larvae be removed by hand, Schwarz 

 found, both the victimized worm and the remaining parasites 

 quickly dry up. After the larva turns yellowish white and relaxes 

 its hold on the caterpillar, it works its way around underneath the 



Fig. 34. — Euplectnis comstockii, How. Adult. 

 (From Fourth Report U. S. Ent.Com.) 



belly of the host and spins a series of silk threads attaching the 

 caterpillar, which is now a mere empty skin, to the leaf. Then 

 the parasitic larvae take their places side by side across the under 

 side of the caterpillar skin, fasten it for nearly its whole length to 

 the leaf, spin a little more loose silk of yellowish white color, and 

 transform to pupae. This silken web does not form a series of 

 cocoons since it is so loose that the black pupae can plainly be 

 seen between its strands. The caterpillar skin protects these 

 pupae just as a roof would do. After first transforming, the pupa is 



59 



