HYMENOPTERA. ~ 377 



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 dirty 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 yellowish. 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 trans- 

 verse wi'inkles, is not rough, and, with a magnifying glass, a few 

 short hairs may be seen scattered over it. After the last moult- 

 ing their color fades, and they become almost yellow. The 

 greater part of them then suddenly leave the trees, either by trav- 

 elling 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 ^nd into other crevices ; but most of those which reach 

 the ground bury themselves under decayed leaves, or among the 

 roots of the grass, and, in such secure places, make their co- 

 coons. The latter are oblong oval cases, of tough grayish silk, 

 and measure nearly three tenths of an inch in length. In due 

 time the insects change to savi^-flies, and come out of their co- 

 coons, one end whereof separates, like a lid, to allow of their 

 escape. Although some of them are found to finish their trans- 

 formations in August, it is probable that the greater part of them 

 remain unchanged in the ground till the following spring^ 



No means for the destruction of the caterpillars of the fir saw- 

 fly have been tried here, except showering them with soap-suds, 

 and with solutions of whale-oil soap, which has been found ef- 

 fectual. They may also be shaken off or beaten from the trees, 

 early in the morning, when they are torpid and easily fall, and 

 may be collected in sheets, and be burned or given to swine. 

 For other means to check their depredations the reader may con- 

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