342 



THE STUDY OF IX SECTS 



short, knobbed antennae are pale yellow. The male is longer and slen- 

 derer and differs somewhat in color. Several varieties of this species, 

 differing in color, have been described. The eggs are laid in June in 

 crescent-shaped slits made in leaves. The food plants are elm, birch, 

 linden, and willow. The larva is greenish-yellow, with black spiracles 

 and a black stripe down its back. When disturbed it spurts forth a 

 fluid from glands just above the spiracles. It clings to the upper surface 

 of a leaf and feeds on the edge of the leaf. When not feeding it rests on 

 one side with the body curled up in a spiral form. There is but one 

 generation each year. When the larva is full-grown it burrows in the 

 ground, makes an oval, brownish cocoon, and there spends the winter, 

 not changing to a pupa until spring. The adults appear in May or June. 



Family Tenthredinid^e 



The Typical Saw/lies 



This is a very large family, including more than seven-eighths of all of 

 the members of the suborder Chalastogastra. 



Fig. 579. — The locust sawfly, Pleronidea Irilineala: 

 a, egg; b, young larva; c, full-grown larva; d, anal seg- 

 ment of full-grown larva; e, cocoon; /, adult. 



The larvae are caterpillar-like; the thoracic legs are always present 

 and are usually well developed, but are vestigial in some species. Prolegs 

 are usually present; these are borne on abdominal segments 2-7 and 10 

 or 2-8 and 10, rarely the prolegs are vestigial. The larvae of the different 

 species differ greatly in size varying from f to if inches in length. 



The larvae of the majority of the species live free on the foliage of 



