TRIOGMA. 303 



forceps, as I have already alluded to above (p. 294), seems to 

 have a different structure. 



Gen. XLII. TRIOGMA. 



First longitudinal vein incurved at the tip towards the second and end- 

 ing in it (and not in the costa) ; a marginal, a subrnarginal, a discal, and 

 four posterior cells ; the small cross-vein is wanting, the subrnarginal cell, 

 at its inner end, being in immediate contact with the discal cell. Antenna^ 

 16-jointed; first joint elongated; joints of the flagellum short subcylin- 

 drical or subglobular, attenuated at the basis ; broader in the male than 

 in the female. Eyes glabrous, separated by a rather broad interval above 

 and below. Tibiae with distinct spurs at the tip. Empodia distinct. 

 Forceps of the male analogous to that of Cylindrotoma ; the aculeus is 

 three-branched, the single branches with a knob at the tip. The ovipositor 

 of the female has short, broad valves, obtuse at the tip. Coloring dull 

 brownish or grayish ; head and thorax conspicuously sculptured with deep 

 punctures. 



Head rather broad posteriorly ; proboscis and palpi rather 

 short. The antennae of the male have more rounded joints of 

 the flagellum than those of the female ; they are clothed on the 

 under side with a delicate pubescence ; in the female these joints 

 are rather subcylindrical ; in both sexes each joint is attenuated 

 at the basis, and there are short verticils about the middle of 

 each (I possess only the male of T. trisulcata, and the female 

 of T. exsculpta). The collare is moderately developed, in the 

 shape of a transverse fold. The thorax of the two species at 

 present known is sculptured in a manner quite unusual among 

 the Tipulidse, and even among the Diptera in general ; there is 

 a more or less distinct groove running from the collare backwards-, 

 along the middle of the mesonotum ; on each side of it, there is 

 a densely rugoso-punctate stripe ; the upper part of the meta- 

 thorax is also densely rugoso-punctate. Feet rather strong, fore 

 coxae short, spurs at the tip of the tibiae of moderate length ; 

 empodia large, distinct ; last joint of the tarsi in the male only 

 slightly excised at the basis on the under side, and its shape not 

 modified. The forceps of the male is very much like that of 

 Cylindrotoma. Although I have not had the opportunity to 

 examine the forceps of living specimens, I could perceive in the 

 dry specimen of a male T. trisulcata the presence of a three- 

 branched aculeus, with knobs at the end of the branches, similar 



