6 l2 
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, Cimbex americana (Cim'bex 
a-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, 
and black legs, while her feet and short, knobbed antennae 
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. 
