APPENDIX. 



705 



Fig. 654. 



temporary hook-like jaws (md) , moving about like a Cestodes 

 embryo with its well known six hooks. The tail moves up and 

 down, but is scarcely used in 

 locomotion. The nervous and 

 vascular systems and tracheae 

 are wanting, while the alimen- ng 

 tary canal is simply a blind 

 sac, remaining in an unorgan- 

 ized state. 



mt 



The second larval state 

 (Fig. 654, o>, oesophagus ; iig, 

 supracesophageal ganglion; 

 ft, nervous cord ; ga and g, 

 genital organs ; ms, bands of 

 muscles) is attained by means 

 of a moult, as usual in the 

 metamorphoses of insects. ffa 

 The cells of the inner layer of g 



Fig. G55. 



the skin 

 ( hypoclcr- 



Second larva of Platygaster. 



mis) now multiply greatly, and give rise to 

 what corresponds to the primitive band of 

 the embryos of other insects. The third 

 larval form is of the usual shape of ich- 

 neumon larvae. 



In Polynema the larva in its first stage 

 is very small and motionless, and with 

 scarcely a trace of organization, being a 

 mere flask-shaped sac of cells. After five 

 or six days, it passes into a worm-like stage 

 and subsequently into a third stage (Fig. 

 655, tg, three pairs of abdominal tubercles 

 destined to form the ovipositor ; /, rudiments 

 of the legs ; /&, portion of the fatty body ; 

 at, rudiments of the antennae, jfl, imaginal 

 discs, or rudiments of the wings). 



The larva of Ophioneurus is at first of 

 the form indicated by Fig. 656 E. It differs from the genera 

 already mentioned, in remaining within its egg membrane and 



Third larva of Polynema. 



