Eruciform Larvae— Larval Types 109 



or the Bees. The bodies of maggots are highly con- 

 tractile ; the head can be drawn far back within the 

 body. In the most degraded types a definite chitinised 

 head capsule is no longer to be found, and the head is 

 merely a fleshy, protrusible " proboscis " armed with 

 hook-like jaws (fig. 68 e,f). The caterpillar, living 

 openly on leaves, breathes through nine pairs of spir- 

 acles (fig. 66\ one prothoracic and eight abdominal 

 pairs. But the fly-maggot, buried in dung, breathes 

 only through a pair of large spiracles on the hindmost 



Fig. 69. — a. Leaf-beetle (Criocerts aspara^t) ; b. egg ; c. young larva ; d. full- 

 grown larva ; e. pupa. Magnified s times. From Chittenden, Yearbook, 

 U.S. Dept. Agr., 1896. 



segment (fig. 68 d). A pair of projecting, fan-shaped 

 spiracles, on the thorax (fig. 68 h) are closed up and 

 useless (4). 



Transition between Larval Types. — The dis- 

 tinction between the campodeiform and eruciform 

 types of larvae, though convenient, cannot be rigidly 

 maintained. Among the Beetles (2, 136) an almost 

 complete transition can be traced from the one to 

 the other. The grub of a Ground-beetle (as described 

 above) or of a Rove-beetle is an active, six-legged 



