858 



Head slightly higher than long; face concave in center; upper half 

 of back of head concave; post-vertical bristles very weak, cruciate; 

 frons in profile slightly buccate, viewed from above nearly one half 

 the width of head, slightly narrowed anteriorly; orbit not differen- 

 tiated from center stripe ; two distinct orbital bristles present on each 

 side which are slightly reclinate and of moderate size ; anterior to the 

 lower one is a short setula ; ocellar bristles f orwardly directed, diverg- 

 ent; surface of center stripe with numerous short setulose hairs; an- 

 tennae rather small, third joint rounded, arista almost as long as frons, 

 bare ; cheeks with numerous rather distinct hairs and 2—3 stronger 

 bristles along mouth margin anteriorly; cheek at middle half as high 

 as eye, the latter slightly longer than high. Mesonotum with 2 pairs 

 of widely separated dorso-central bristles, the anterior pair much 

 weaker than the posterior and preceded by a closely placed series of 

 short setulse which extend along the inner margin of the lateral vittse 

 almost to anterior margin of disc; acrostichals two-rowed anteriorly, 

 irregularly four-rowed posteriorly; no bristles between posterior 

 dorso-centrals ; scutellum slightly flattened on disc, 4 subequal mar- 

 ginal bristles present, the posterior pair located on margin very close 

 to base. Abdomen slightly elongated, pointed at apex. Legs rather 

 slender ; tibiae without preapical bristle. Wings narrow, auxiliary vein 

 complete but indistinct ; costa unbroken, first division one fifth as long 

 as second ; second vein distinctly arcuate, the cell between it and third 

 vein conspicuously narrowed apically; inner cross-vein about as far 

 beyond apex of first as it is in front of outer cross-vein ; outer cross- 

 vein short, not much longer than inner; last section of fourth vein four 

 times as long as penultimate; last section of fifth, one and a half times 

 as long as penultimate. 



Length, 2 mm. 



Type locality, Urbana, III., June 19 to July 9, 191 5 ; on window in 

 Natural History Building, University of Illinois (J. R. Malloch). 



The range of variation in color in this species includes forms in 

 which the back of the head is entirely gray, and the dorsum of thorax 

 and abdomen almost entirely blackish gray. 



The genus Aphantosoma was described by Becker in 1903*, who 

 distinguished it from Chyroniyia by the concave occiput, the latter 

 genus having the occiput convex. The characters of the two genera 

 are very similar, but the shape of the head should readily separate 

 them. The Egyptian species, approximatum Becker, differs from the 

 above species in having the disc of the mesonotum opaque gray dusted 

 and the pleurae with gray spots. It is also considerably smaller — 

 •5-75 mm . 



"Aegyptische Dipteren. Mitt. Zool. Mus. Berlin, II Bd., 3 Hft. 



