6l2 THE STUDY OF INSECTS. 



true caterpillars have only ten.* Most saw-fly larvae have 

 the curious habit of curling the hind end of the body side- 

 wise. 



The saw-fly larvae make parchment-like cocoons which 

 they sometimes attach to the plants on which they have 

 fed ; but they often burrow in the ground and spin their co- 

 coons there. The adult saw-fly lays its eggs upon the food 

 plant, and in some strange way, perhaps by the absorption 

 of moisture, the eggs increase in size before they hatch. 

 The saws of the female are set side by side in a groove un- 

 der the end of the body like the blades of a penknife in the 

 handle. These saws can be shoved out and moved up and 

 down. Here we have at least one instance where the fe- 

 male wielding of a saw is done most skilfully, for the female 

 saw-fly uses these nice tools in a very efficient manner to 

 make slits in the leaves and stems of plants in which she 

 places her eggs. 



The American Saw-fly, Ciuibcx aniericaiia (Cim'bex 

 p-mer-i-ca'na). - This is the largest of our common saw-flies. 

 The female is about three fourths of an inch long and has a 

 black head and thorax, a steel-blue or purplish abdomen, 

 with four yellowish spots on each side, smoky brown wings, 

 ind black legs, while her feet and short, knobbed antennas 

 are pale yellow. The male is longer and slenderer, and dif- 

 fers somewhat in color. The eggs are laid in June in cres- 

 cent-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 dis- 

 turbed it spurts forth a fluid from glands just above the 

 spiracles. There is but one brood each year. After the 

 larva is grown it burrows in the ground, makes an oval brown- 

 ish cocoon, and there spends the winter, not changing to a 

 pupa until spring. The adult appears in May or June. These 

 saw-flies have been known to injure willows by biting inci- 



* Except in the Megalopygidae, see p. 219. 



