522 HYMENOPTERA. 



become almost yellow. The greater part of them then sud- 

 denly 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 roots of the grass, and in such secure 

 places make their cocoons. 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 

 saw-flies, and come out of their cocoons, one end whereof 

 separates, like a lid, to allow of their escape. Although 

 some of them are found to finish their transformations 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 soapsuds, and with solutions of whale-oil soap, which 

 has been found effectual. 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 consult the arti- 

 cles on the pine and fir saw-flies of Europe, contained in 

 Kollar's "Treatise." 



The following account of a kind of saw-fly which at- 

 tacks the grape-vine is chiefly extracted from my Discourse 

 before the Massachusetts Horticultural Society, in 1832, 

 where the insect is named Selandria Vitis. The saw-fly 

 of the vine is of a jet-black color, except the upper side 

 of the thorax, which is red, and the fore legs and under 

 side of. the other legs, which are pale yellow or whitish. 

 The wings are semitransparent, of a smoky color, with 



