368 THE CANADIAN ENTOMOLOGIST 



The embryo requires from twelve days to three weeks to com- 

 plete its development, the length of time varying considerably 

 with the species. While the larva of each species passes through 

 a definite number of instars, the number varies considerable among 

 the different groups of species. The larvae usually require about 

 fifteen days for the completion of their growth. 



There is great variation in their method of feeding. The 

 great majority of the nematids are edge feeders; they cling to the 

 edge of the leaf with the thoracic legs and when disturbed, bend 

 their abdomen back onto the thorax in an S-shaped curve. Many 

 emphytids and selandriids rest wnth their body stretched out flat on 

 the underside of the leaf and eat holes in the leaf or feed from the 

 edge; others, while feeding in a similar manner, rest with the body 

 curled helix-like, with the anal prolegs forming the apex of the helix. 

 This is also true of the cimbicids, Cimhex and Trichiosoma, which 

 are edge feeders, resting curled on the upper surface of the leaf. A 

 few nematids and selandriids also feed on the upper surface — some 

 with the body helix-like, others extended. The phyllotomids, in- 

 cluding the genus Caliroa, are leaf skeletonizers, feeding only on 

 the parenchyma of the under surface. The very young larvae of 

 many of the groups are also skeletonizers during the first or second 

 instars. The lophyrids, which feed only on conifers, begin at the 

 the free end of the needle, clasping it between the prolegs, and eat 

 towards its base until only a stub is left. The dolerids, or what I 

 believe to belong to this group, for none of the American species 

 have been bred, feed on sedges (Carex), feeding on the ends of the 

 blades; the same is true of some of the grass-feeding nematids. 

 The pamphiliids are either gregarious, when they fasten several 

 leaves together into a nest with threads of silk, or solitary, when 

 they roll the edge of the leaf and fasten it together with silk. 

 These larvae are the only ones, so far as I know, that use silk in 

 this way. The fenusids and scolioneurids are leaf miners. 



The body of the larva may be either black, white, green, 

 spotted or banded. A large proportion of the species are white or 

 green. In the green species the colour is due, in great part, to the 

 colour of the blood and the food contained in the alimentary canal. 

 They are also usually banded dorsally (the dorsal blood vessel) and 

 marked on each side of this band and along the pleura by frosted 



