196 DISEASES OP THE ROSE. 



one-fifth of an inch or more, and the wings expand nearly or quite 

 two-fifths of an inch. These saw-flies come out of the ground, at 

 various times, between the twentieth of May and the middle of 

 June, during which period they pair and lay their eggs. The 

 females do not fly much, and may be seen, during most of the 

 day, resting on the leaves ; and, when touched, they draw up 

 their legs, and fall to the ground. The males are more active, 

 fly from one rose-bush to another, and hover around their slug- 

 gish partners. The latter, when about to lay their eggs, turn a 

 little on one side, unsheathe their saws, and thrust them oblique- 

 ly into the skin of the leaf, depositing in each incision thus made, 

 a single egg. The young begin to hatch in ten days or a fortnight 

 after the eggs are laid. They may sometimes be found on the 

 leaves as early as the first of June, but do not usually appear in 

 considerable numbers till the twentieth of the same month. How 

 long they are in coming to maturity, I have not particularly ob- 

 served ; but the period of their existence in the caterpillar state 

 probably does not exceed three weeks. They somewhat resemble 

 the young of the saw-fly in form, but are not quite so convex. 

 They have a small, round, yellowish head, with a black dot on 

 each side of it, and are provided with twenty-two short legs. 

 The body is green above, paler at the sides, and yellowish 

 beneath ; and it is soft, and almost transparent like jelly. The 

 skin of the back is transversely wrinkled, and covered with mi- 

 nute elevated points ; and there are two small, triple-pointed 

 warts on the edge of the first ring, immediately behind the head. 

 These gelatinous and sluggish creatures eat the upper surface of 

 the leaf in large irregular patches, leaving the veins and the skin 

 beneath untouched ; and they are sometimes so thick that 

 not a leaf on the bushes is spared by them, and the whole foliage 

 looks as if it had been scorched by fire, and drops off soon after- 

 ward. They cast their skins several times, leaving them ex- 

 tended and fastened on the leaves ; after the last moulting they 

 lose their semi-transparent and greenish color, and acquire an 

 opake yellowish hue. They then leave the rose-bushes, some of 

 them slowly creeping down the stem, and others rolling up and 

 dropping off, especially when the bushes are shaken by the wind. 

 Having reached the ground, they burrow to the depth of an inch 

 or more in the earth, where each one makes for itself a small oval 

 cell, of grains of earth, cemented with a little gummy silk. Hav- 

 ing finished their transformations, and turned to flies, within 



