THE CANADIAN ENTOMOLOGIST 369 



lines (the dorsal pleural air tubes). A few species arc marked on 

 the dorsum and some on the pleura adjacent to the spiracles of 

 certain segments by large yellow patches, which are due to lobes 

 of adipose tissue or fat, which show through the cuticle. Many 

 species are marked with pigmented colours; only one so far as ob- 

 served has a median dorsal line, Cimbex. There is great variation 

 in the arrangement and time of appearance of these colours. The 

 entire body may be black or brown, or consist of longitudinal or 

 tranverse rows of spots. Larvae that are white when they emerge 

 from the egg, may be entirely or almost black or chocolate brown 

 in the latter part of their larval life, while those that are black 

 w^hen they emerge from the egg, may be almost entirely light- 

 coloured when mature. 



The larva?, when fully fed, moult their skins and seek a place 

 for pupation. This last moult may take place before they leave 

 the host plant or after that time. There is no striking difference 

 in the form and appearance of the body of most of the green or 

 white larvae, but those with prominent spines and black spots loosen 

 the spines and spots and become opaque white; some that are white 

 become distinctly spotted; some that are black or black-spotted 

 become green, white, or glassy green, and still others that are 

 opaque white through all the preceding stages have black spots 

 about where the setae were located. This diversity in form in the 

 different stages makes it very difficult, until both stages have been 

 recognized for a given species, to determine whether you are work- 

 ing with one or two species. This last larval stage has been 

 designated as the ultimate stage by Dyar, who has done more 

 toward elucidating the life-histories of the American species of 

 sawflies than all the other workers together. 



After the assumption of the ultimate stage some larvae remain 

 quiet for a time, resting upon the food plant; but the great ma- 

 jority leave the host plant and wander about in search of a place 

 to prepare for pupation. The xyelids, pamphiliids, and blenno- 

 campids form cells in the ground, the emphytids and selandriids 

 bore into rotten wood; also some nematids, which have the same 

 habit, and so far as observed all these have a striking ultimate 

 stage. The end of the tunnel is plugged with frass and the cavity 

 left unlined with silk except a few species, which make a very thin 



