412 INSECTS INJURIOUS TO VEGETATION. 



My specimens of this kind of saw-fly, which were raised from 

 the caterpillars in the summer of 1838, came out of their 

 cocoons towards the end of July in the same year; but I have 

 also found them on pines and firs early in May. The Euro- 

 pean pine saw-flies lay their eggs in slits which they make 

 with their saws in the edges of the leaves ; and it is probable 

 that our fir saw-flies proceed in the same way. In June and 

 July the false caterpillars of the latter may be found on firs ; 

 and, according to notes made by me many years ago, the same 

 insects, or some very much like them, were observed on the 

 leaves of the pitch-pine also. They are social in their habits, 

 living together in considerable swarms, and so thick that some- 

 times two may be seen feeding together on the same leaf, and 

 sitting opposite to each other. In order to lay hold of the leaf 

 more firmly they curl the hinder part of the body around it; 

 and, if they are disturbed, they throw up their heads and tails 

 with a jerking motion. When fully grown, they are from five 

 to six tenths of an inch in length ; they are nearly cylindrical 

 in form, thickest before the middle, and tapering behind, and 

 have twenty-two legs. The head, and the first three pairs of 

 legs, are black. The body is of a pale and du'ty green color 

 above, with a light stripe along the top of the back, separating 

 two of a darker green color; there are two dark green stripes 

 on each side of the body; and the belly and proplegs are yel- 

 lowish. When young, the two stripes on the back are much 

 darker, and those on the sides are nearly black. The skin, 

 though covered with very fine transverse wrinkles, is not rough, 

 and, with a magnifying glass, a few short hau's may be seen 

 scattered over it. After the last moulting their color fades, 

 and they become almost yellow. The gi'eater part of them 

 then suddenly leave the trees, either by travelling down the 

 trunks, or by falling from the branches to the ground. A few, 

 either from weakness or from some other cause, remain on the 

 trees, make their cocoons among the leaves, and rarely finish 

 their transformations, most of them perishing from the internal 

 attacks of ichneumon-grubs. Some creep into cracks in fences 

 and into other crevices; but most of those which reach the 

 ground bury themselves under decayed leaves, or among the 



