THE HESSIAN-FLY 



135 



(Cecidomyia), exhibit this peculiarity, and pupate without 

 casting the larval skin. So also do the blow-fly and its near 

 allies, the higher Diptera. 



Mr Enock has worked out the changes which take place 

 within the flax-seed. The body of 

 the insect first shrinks away from 

 its envelope, "just as a ripe nut 

 shrinks from its shell." Next it 

 turns itself about, head for tail, 

 within the husk — a task of some 

 difficulty, for the space is Uttle fv . d r u • a 



1 ■ W. ii. i_ J 1 • 1 '^^- 75-— Pupa of Hessian-fly, 



Digger tnan the body which OCCU- escaping from larval skin, magni- 



pies it. This reversal of the ''"^■ 

 two ends of the body facilitates the subsequent escape 

 of the pupa. So long as the insect was feeding on the 

 fluids sucked from the joint it kept the original attitude, 

 with head directed downwards — the attitude in which it 

 quitted the egg, and crept down the sheath. But the first 

 thing which the pupa has to do is to crawl up the sheath 



Fig. 76. — Hessian-fly. X 10. 



again, and work its way out. To prepare for this, it brings 

 the head round till it points upwards. Mr Enock believes 

 that the two-pronged scale on the under side of the prothorax 

 finds its special use in this turning movement. When all 



