ATTACKING THE LEAVES. 151 



the United States and Canada, injuring more or less seriously 

 the foliage of our pear, cherry, quince, and plum trees every 

 year. 



This insect passes the winter in the chrysalis state under 

 ground ; the flies, the progenitors of the mischievous brood 

 of slugs, appearing on the wing in the Northern States and 

 Canada from about the third week in May until the middle 

 of June. The fly (Fig. 159) is of a glossy black color, 

 with four transparent wings, the front pair 

 being crossed by a dusky cloud ; the veins ^i^. 159. 

 are brownish, and the legs dull yellow, with 

 black thighs, except the hind pair, which are 

 black at both extremities, and dull yellow in 

 the middle. The female fly is more than 

 one-fifth of an inch long ; the male is somewhat smaller. 

 When the trees on which these flies are at work are jarred 

 or shaken, or if the flies are otherwise disturbed, they fall to 

 the ground, where, folding their antennae under their bodies 

 and bending the head forward and under, they remain for a 

 time motionless. 



The saw-flies liave been so called from the fact that in most 

 of the species the females are provided with a saw-like ap- 

 pendage at the end of the body, by which slits are cut in the 

 leaves of the trees, shrubs, or plants on which the larvae feed, 

 in which slits the eggs are deposited. The female of this 

 species begins to deposit her eggs early in June; they are 

 placed singly within little semicircular incisions through the 

 skin of the leaf, sometimes on the under side and sometimes 

 on the upper. In about a fortnight these eggs hatch. 



The newly-hatched slug is at first white, but soon a slimy 

 matter oozes out of the skin and covers the upper part of the 

 body with an olive-colored sticky coating. After changing 

 its skin four times, it attains the length of half an inch or more 

 (see Fig. 160, a), and is then nearly full grown. It is a dis- 

 gusting-looking creature, a slimy, blackish, or olive-brown 

 slug, with the anterior part of its body so swollen as to re- 



