270 



narrowly interrupted on middle line ; prothoracic spiracle elevated, the 

 protuberance nearly twice as long as thick. Membranous portions of 

 thorax and abdomen covered with numerous very short spinules ; 

 chitinized plates on dorsum with a number of long hairs and many 

 short spines (Fig. 8) ; anterior and posterior annuli of abdominal seg- 

 ments each with long lateral hairs, the median one with a short, stout 

 lateral protuberance which has the appearance of a rudimentary spir- 

 acle; ventral segments with a transverse series of long hairs on each 

 of the intermediate (4) and posterior (4-6) annuli, those on the 

 former inserted in small round dark plates; apical segment about 1.5 

 as long as wide, armed with a number of dorsal and lateral hairs, ven- 

 tral surface with a large chitinized plate, the rounded apex of which 

 is armed with a fringe of long stiff hairs ; laterad of this plate and 

 near its margin is a small rounded plate upon which are 2 long hairs; 

 apex of segment above terminating in 4 short clubbed processes which 

 are fringed with a number of long radiating hairs (Fig. 15). 



Pupa (PI. XXXIX, Fig. 10). — Length, 3.5 mm. Brownish tes- 

 taceous, not shining. 



Prothoracic respiratory organs (Fig. 6) slightly tapering at base 

 and apex, surfaces honeycombed or shagreened and with a number 

 of small tracheal openings. Ventral aspect of pupa as in Figure 10, 

 the transverse abdominal armature in 2 rows on each segment, the 

 anterior row consisting of 4 widely placed spinules on disc and one 

 on each lateral margin, the posterior row of numerous closely placed 

 spinules, the apices of some of which are irregularly dentate ; dorsal 

 segments, except basal, each with a single transverse series of spinules 

 on posterior margin which is similar to that on ventral segments, and 

 also, like that series with 4 longer hairs (Fig. 4) ; apical segment with 

 tlie upper posterior margin armed with 2 very short thorns, the lower 

 posterior margin with 2 long, curved thorns (Fig. 2). 



The foregoing descriptions are drawn from larval and pupal ma- 

 terial obtained from water in a tree-hole in the forestrv of the l^ni- 

 versity of Illinois at Urbana June 2, 1916. The duration of the pupal 

 stage averaged three days under laboratory conditions. 



The species was originally described from imagines obtained at 

 Sea Cliff, N. Y., and has been recorded from Battle Creek, Mich. I 

 took imagines on tree-trunks at Urbana in July and August, 191 5. 



The larva bears a striking resemblance to that of Pcricoma caues- 

 cens Meigen as figured by Miall and Walker*, but differs in the ar- 



*Trans. Ent. Soe. London, 1895, PI. III. 



