OF THE SAW-FLIES (TENTHREDINID^). 133 



Lyda inanita is another species of saw-fly, which in its 

 larva state attacks the leaves of the roses, but it is peculiar 

 on account of the remarkable instinct with which it is en- 

 dowed, which leads it to construct a moveable case, formed 

 of small strips of the leaves arranged in a spiral direction, 

 within which it resides, and which gives it a general resem- 

 blance, not only to the Caddis-larvas of the Trickoptera, but 

 also to the aquatic larva of the China-mark moths {Hydro- 

 campa). The larvae of the genus Lyda are the only ones in 

 the family which are destitute of the false or ventral prolegs. 

 Towards the end of June and through the month of July 

 I observed, upon different varieties of roses in my garden at 

 Hammersmith, the cases of these larvae of various sizes, each 

 being a cylinder or rather an elongated cone, the slender 

 extremity being free, whilst the other end is often still con- 

 nected with the leaf by the strip not being entirely severed 

 from it. The larva, in fact, by degrees cuts off one edge of 

 the leaf, thereby forming a strip about one-eighth of an inch 

 wide, at the same time eating a portion of the leaf imme- 

 diately adjoining the slit which it has made ; the free end of 

 the strip is gradually fastened in a whorl round the insect's 

 body by the help of slender threads of silk, whilst the other 

 end of the strip is only detached from the leaf when the 

 larva has arrived at its extremity ; it has the further instinct 

 to twist the strip downwards, working beneath it, hidden from 

 above ; it moreover arranges the serrated edge of the leaf on 

 the outside of its case, so that wet is thrown off, just as by 

 the tiles of the roof of a house. The roll, when the insect is 

 full grown, is nearly two inches long ; it is then, however, 

 formed by the addition of strips cut from several leaves. 

 The full grown larva is nearly an inch long, of a dirty- 

 green colour, with three pairs of jointed legs, and a pair of 

 laterally projected, slender, 3-jointed feeler-like organs, at- 



