18 PROCEEDINGS OF THE NATIONAL MUSEUM tol. G8 



metapneustic. Tho buccopharyngeal apparatus (pi. 5, figs. 30, 31, 

 32, 33) is moderately strong, the mouth hooks being much shorter and 

 less massive than the basal piece. The median hook is heavily chitin- 

 ized; the lateral hooks are not fused at the tip with the median hook, 

 but terminate in well defined tips, similar to the tip of the median 

 hook, in outline, but much less strongly chitinized. The median 

 hook articulates with a slender intermediate region which is in turn 

 firmly fused to the basal piece. The sides of the intermediate region 

 are joined ventrally by a sclerite, which in lateral view appears barb- 

 like, and which viewed from above gives the region an H-like appear- 

 ance. The large basal piece consists of a single ventral and two 

 dorsal wings which are not cleft on their posterior margins. This 

 agrees in every particular with Thompson's description of the first 

 instar maggot of SpJiecapata conicaP 



S. trilineata is the only species in which the second instar maggot 

 has been studied. The body is Vvdiite, with transparent cuticle 

 through which the internal organs are plainly visible. The cuticle 

 of the first four segments bears irregular rows of minute black spines 

 confined to an encircling belt on the anterior third of the segment. 

 In this instar, the maggot is amphipneustic, the anterior spiracle 

 terminating in several fingerlike papillae spread fanlike and pro- 

 truding conspicuously from the body. The buccopharyngeal ap- 

 paratus differs from that of the first instar maggot in several par- 

 ticulars (pi. 5, fig. 34). There are two strong lateral hooks but no 

 median hook ; the intermediate piece articulates freely with the basal 

 piece as well as the bucal hooks ; the superior wing of the basal piece 

 has at its posterior margin, two prolongations separated by a deep 

 cleft ; and dorsal to the intermediate region is a weak vestigial sclerite 

 called the dorsal accessory piece. 



The puparia of three species have been studied (pi. 4, fig. 21). 

 They arc characterized as follows: Yellowish to chestnut-brown in 

 color, rather smooth and thin-walled; with minute brown spines on 

 the anterior third or less of the segment, spiniferous areas encircling 

 the segments anteriorly, limited to the ventral surface posteriorly; 

 round in cross section; from the lateral aspect, oval save for the ex- 

 treme posterior margin which is truncate. Anterior spiracle pro- 

 truding, terminating in several fingerlike papillae, radiating fanlike 

 from the base; posterior spiracles located in distinct shield-shaped 

 pit (pi. 5, fig. 27), centered on the longitudinal axis; spiracles located 

 at the upper part of the pit, separated by at least their diameter, 

 broadly rounded above, tapering to a point below; button indistinct; 

 anal opening large and located at some distance below the pit. 



Several species of this genus are widely distributed over North 

 America, at least one of which occurs as far southward as Peru, in 



•' Recherches Sur. Ics Diptercs parasites, p. 105, fig. 109. 



