II.] 



METAMORPHOSES OF INSECTS. 



35 



Ganin met with the larvae of Platygaster in those 

 of a small gnat, Cecidomyia. Sometimes as many as 

 fifteen parasites occurred in one gnat, but as a rule 

 only one of these attained maturity. The three 

 species of Platygaster differ considerably in form, as 

 shown in Figs. 23 25. They creep about within 

 the larva of Cecidomyia by means of the strong 

 hooked feet, kf> somewhat aided by movements 

 of the tail. They possess a mouth, stomach, and 

 muscles, but the nervous, vascular, and respiratory 



FIG. 17, Egg of Platygaster (after Ganin). 18, Egg of Platygaster 

 showing the central cell. 19, Egg of Platygaster after the division of 

 the central wall 20, Egg of Platygaster more advanced. 21, Egg of 

 Platygaster more advanced. 22, Egg of Platygaster showing the rudi- 

 ment of the embryo. 



systems do not make their appearance until later. 

 After some time the larva (Fig. 23) changes its 

 skin, assuming the form represented in Fig. 26. In 

 this moult the last abdominal segment of the first 

 larva is entirely thrown off: not merely the outer 

 skin, as in the case of the other segments, but also 



D 2 



