28 STRUCTUKE OF CERTAIN DIPTEROUS LARV^. 



form areas not prominent, a transverse line on ventral middle of 

 most segments; the anal area shows four hispid tubercles in a trans- 

 verse row; stigmal plates black, a little elevated, each with three 

 short pointed slits, and a button; a pair of cones above and a pair of 

 smaller cones below stigmal plates. 



In orange from Mexico, with Trypeta ludens, No. 4242. 



^ Muscid D. 



(Plate II, figs. 34, 35.) 



Body long and slender, the bilobed head with small papilla; two 

 great hooks; anterior spiracles with about six lobes; a narrow, 

 fusiform, swollen area on the ventral base of the segments beyond 4, 

 each with transverse ridges; a transverse line on ventral middle of 

 these segMients; lateral fusiform areas distinct; tip of body large and 

 truncate, no distinct tubercles but two low humps above and less 

 distinct ones below the stigmal plates; latter small, about their 

 diameter apart, each with three rather short, subparallel slits, and 

 directed toward those of opposite plate, the button distinct. Anal 

 area with three smooth, rounded tubercles each side, and a less 

 distinct median one, each tubercle with a few fine grooves on tip; 

 a transverse granulatetl ridge in front of the anal tubercles. 



From Alaska, probably taken on cabbage. 



HOMALOMYIA GROUP. 



The larva of Homalomyia has long been known because of its 

 peculiar appearance, and the frequency with which it is associated 

 with human food. These larvae are flat and fusiform, each segment 

 provided with long bristly processes. The mouth parts are obscure, 

 and the stigmal plates occupy a dorsal position on the last segment of 

 the body. 



So very different are these larvae from the ordinary anthomyiid 

 larvae that they should stand in a group by themselves. 



Homalomyia sp. 

 (Plate VI, fig. 106.) 



The larva of the genus Homalomyia is entirely dift'erent in general 

 appearance from any of the other forms considered in this paper. 

 The body is flattened, and bears above a pair of long spinous processes 

 on each segment, forming two submedian rows; there is a row of 

 similar processes on each upper and lower side, making six rows of 

 these processes on the body; on the head is a pair of anteriorly- 

 directed processes, and the last segment, whose posterior surface is 

 apparently turned upward, has two of these processes on each side. 



