THE SAW-FLIES. 229 



formation that the insect passes into the pupa state. 

 The largest British species of the group, Cimbex 

 femorata, is said to remain two years in its cocoon 

 before appearing in the perfect state ; it varies greatly 

 in colour, from yellow, with dark or black markings, 

 to black, with the clavate antennae and the tarsi yel- 

 low, and the hinder thighs are much thickened in the 

 male. The commonest of the species with clavate 

 antennae is the Trichiosoma lucorum, an insect about 

 half an inch in length, of a very stout form, and a 

 blackish- brown colour, clothed with greyish-brown 

 hair. Its larva occurs frequently in August upon 

 the White Thorn, and the cocoon, which is of very- 

 large size, may often be seen attached to the bare 

 branches of this tree in the spring. The perfect 

 insect is usually to be met with about hedges in 

 May. 



Although the majority of the larvae of this tribe 

 feed boldly upon the leaves of plants, the action of 

 the ovipositor in some instances causes the growth 

 of an excrescence or gall at the part of the plant 

 wounded by it, in the interior of which the larva 

 feeds and comes to maturity. These galls are gene- 

 rally found in the leaves, and most of those hitherto 

 observed have been upon different kinds of willows : 

 the insects producing them belong to the same genus 

 as the gooseberry-grub. 



Many other species besides the one just mentioned 

 are exceedingly destructive to the produce of our 

 gardens, fields, and woods. The Nematus Caprea, a 

 species which feeds on the leaves of willows, has 

 occasionally done great mischief to osier-beds ; several 

 species of Lophyrus (L. Pini, &c.) feed upon the leaves 

 of Pine and Fir trees, to which they are exceedingly 



