AMERICAN DIPTERA. 66l 



with small hairs arranged in transverse rows, largesl al the edges of 

 the segments. 



Only the wingless female of this genus is known, represented by 

 the type species ./•;. blattoides Mein., from Denmark, ami by .11. 

 schwartzii Coq., from Arizona in tins country. 



Table of Species. 



Abdomen with four free segments schwartzii Coq, 



Abdomen with five free segments I»lal luidcs Mein. 



J3nigmatias schwartzii Coq. 

 Coquillett, Canadian Entomologist, xxv, 20. 



D;irk yellow, the posterior part of the body segments In-own, most extended 

 on the apical part of the abdomen, where it covers the genitalia and the greater 

 portion of the last two segments ; upper side of body opaque, distinctly whitish - 

 pruinose, and with a short, sparse, yellowish-white pubescence, a row of short 

 black bristles along the hind margin of each abdominal segment and a few 

 shorter ones scattered over the last two segments; first thoracic segment (which 

 comprises the prothorax and mesothorax) slightly over twice as long as the sec- 

 ond, the latter almost twice as long as the first abdominal segment and subequal 

 to the second, about two-thirds as long as the third, the fourth segment deeply 

 emarginate in the middle, at which point it is slightly shorter than the first 

 abdominal segment ; greatest vertical diameter of abdomen scarcely more than 

 that of the thorax, venter convex (and without the blackish protuberance shown 

 in Dr. Meinert's figure 2); head sparsely clothed with a short, yellowish-white 

 pubescence, a row of black post-ocular bristles extends from the upper end of 

 each eye to the oral margin, apices of palpi beset with a dense cluster of black 

 bristles; legs beset with short, black, bristly hairs, femora very robust. 



Length 1.5 mm. 



Type locality, Flagstaff, Arizona. Type No. 6703, U. S. National 

 Museum. 



In regard to its habits, Mr. Coquillett gives the following note : 

 "Of its habits nothing is known beyond the fact that it occurred on 

 low vegetation in a locality where no ant-nests could be found, al- 

 though search was made for them. No stones or rocks occurred in 

 the immediate vicinity, the nearest approach being the small pieces 

 of lava scattered about, but these were too small to conceal an 



ant-nest." 



ECITOMYIA Braes. 



1901. Brues, American Naturalist, p. 347. 



Male. Small, rather slender species. Head with large antenna! 

 cavities; antennae with spherical third joint and apical arista; an- 

 terior frontal bristles porrect. Front broader than long, with three 



TRANS. AM. KNT. SOC. XXIX. DECEMBER. 1903 



