J. R. MALLOCH • 149 



The male differs from typical species placed in Linmophoro 

 less conspicuously than does aeqidfrons Stein or arcuata Stein, 

 and until it is possible for some one to revise the group thor- 

 ouojily I consider it advisable to leave the species in Limnophora, 

 the more so as I do not clearly understand the subdivisions of 

 the genus proposed by recent European authors. 



I append a brief description of the male of hrevicornis. 



Male. — Color as in female, grayish white, basal dorsal segment of abdomen 

 black on a large portion of disc, second segment witli a pair of large subtri- 

 angular lilack spots, third segment with a pair of small blackish spots which 

 are at times indistinct. Orbits, face and cheeks silvery. 



Eyes separated by a little more than width across i)osterior ocelli, orbits 

 almost or quite obliterating interfrontalia, each with five or six bristles along 

 inner margin, otherwise bare. Acrostichals two-rowed. Hind femur with 

 loTig slender bristles on basal half of posterior surface, postero-ventral sur- 

 face bare. Otherwise as female. Length, 4 mm. 



Allotype. — cf ; Waukegan, Illinois, August 24, 1917, (J. R. 

 Malloch), [Illinois]. Three other specimens with same data. 



The species occurred on the bare sand on tiie shore of Lake 

 Michigan. 



Limnophora argentiventris sji. n. 



Male. — Differs from the preceding species in having the ocellar triangle 

 black and the abdomen silvery, with smaller black dorsal spots. 



Structurally similar to brevicorrm, but cheek slightly higher than width 

 of })arafrontal at base of antennae. In addition to the elongated fourth 

 torgite this .species differs from brevicornis in having the basal portion of 

 hypopygium with a long bristle on each side close to central cleft, all sternites 

 with more numerous hairs, the fifth distinctly produced at apex of each 

 process, and the hind femur with a few slender bristles at base on postero- 

 ventral surface and without the posterior bristles. Length, 3.5 mm. 



Type. — cT; Gallatin County, Montana, August 23, 1917, 

 [Mont. Exp. Sta.]. 



Limnophora obsoleta sj). n. 



Mail'. — Black, subopaque, tlie abdomen slightly shining. Orbits, face 

 and cheeks with .silvery gray pruinescence. Thorax with slight gray pruines- 

 cence, which is most distinct on lateral margins and on the narrow vittae 

 on each side of the median line on disc. Abdomen almost entirely black, 

 the posterior margins of the tergites brownish, the dorsal spots indistinguish- 

 able. Legs entirely black. Wings slightly and evenly browned, veins thick, 

 dark brown. Calyptrae obscurely yellowish. Halteres pale brown. 



Ej'es bare, se]iarated at narrowest i)art of frons by a distance about 1..5 

 as great as width across posterior ocelli, the interfrontalia as wide as one 



TH.\NS. A.M. KXT. SOC, XLVI. 



