158 



ENTOMOLOGY 



are probably carried by the host to flowers or other places where they 

 are able to attach themselves to the bodies of their future hosts. After 

 penetrating into the body of the host the larva grows rapidly; with the 

 first molt the eyes and legs are lost, the second instar being scarabae- 

 idoid in form; after the second molt the male and female larvae differ 

 in development. 



The most extraordinary metamorphoses have been found among 

 parasitic Hymenoptera, as in Platygaster, a proctotrypid which infests 

 the larva of Cecidomyia. The egg of Platygaster, according to Ganin, 



FIG. 221. Stages in the hypermetamorphosis of Platygaster. A, first larva; B, second 

 larva; C, third larva; a, antenna; b, brain;/, fat-tissue; h, hind intestine; m, mandible; mo, 

 mouth; ms, muscle; n, nerve cord; r, reproductive organ of one side; s, salivary gland; t, 

 trachea. After GANIN. 



hatches into a larva of bizarre form (Fig. 221, A), suggesting the crusta- 

 cean Cyclops, rather than an insect. This first larva has a blind food 

 canal and no nervous, circulatory or respiratory systems. After a 

 molt the outline is oval (B) , and there are no appendages as yet, though 

 the nervous system is partially developed. Another molt, and the 

 third larva appears (C), elliptical in contour, externally segmented, with 

 tracheae and a pair of mandibles. From now on, the development is 

 essentially like that of other parasitic Hymenoptera. 



Equally anomalous are the changes undergone by Polynema, a proc- 

 totrypid parasite in the eggs of dragon flies, and by the proctotrypid 

 Teleas, which affects the eggs of the tree cricke\(Ecanthus) . In all 

 these cases the larvae go through changes which in most other insects are 

 confined to the egg stage. In other words, the larva hatches before its 

 embryonic development is completed, so to speak. 



