AMERICAN DIPTERA. 273 



On account of the rarely fuscous base of the abdomen, tliis spe- 

 cies may become confused with basalts Loew, from which it may be 

 readily distinguished by the brownish thoracic bristles. 



This species, together with nugax sp. nov., is the Hilara men- 

 tioned by Mr. Wheeler in his paper on "Anemotropism and other 

 Tropisms in Insects, p. 875,"* as dancing in swarms. 



Hilara nugax sp. nov. 

 This species differs from congregaria as follows : 



1/ate.— Thoracic and cephalic bristles slightly longer and stouter, darker, 

 piceous or black. Antennal style more slender. Palpi piceous, with darker 

 hairs. Hypopygial lamellse not serrated. Legs darker testaceous, piceous or 

 black from the middle of the tibife ; anterior metatarsi without long hairs above, 

 underside straight. Halteres fuscous. Wings cinereous hyaline ; veins darker 

 fuscous, stigma dark fuscons. 



Female. — Differs from the male thus: legs lighter in color, tibife with more red- 

 dish, metatarsi not incrassate. The hind tibiae of the female are not at all thick- 

 ened. 



Twenty nine males and twenty-four females; Monterey Co., Cali- 

 fornia, July 3 to 23, 189B. Collected by Dr. Wheeler. 



H<»RIVIOPEZA Zetterstedt. 



Rather small species. AntennsB much shorter than the head, 

 apparently two-jointed, the terminal joint ovate, compressed, with 

 a short, thick end- bristle. Eyes of the male contiguous above. 

 Hypopygium of the male rounded, consisting of two convex, shin- 

 ing, hemispherical plates, between which reaches a short hairy pro- 

 cess. Legs simple. Wings as in Hilara. 



The species are distinguished from Hilara by the contiguous eyes 

 of the males, the simple metatarsi of the males, and by the structure 

 of the antennse. 



Stigma and veins fuscous; third antennal joint oval ; knob of halteres blackish. 



nigricans Loew. 



No stigma, veins pale 2. 



2. Third antennal joint oval ; halteres and legs luteous bullata sp. nov. 



Third antennal joint globose; halteres and legs fuscous. 



breTicornis Loew. 



Horniopeza brevicoruis Loew (Fig. 87). 

 Cent. V, 65. 



Head black, eyes of the male contiguous. Front shining above the antennae. 



* Archiv fuer Entwickelungsmechanik der Organismen. 8th Band, 3rd Heft. 

 1899. 



TRANS. AM. ENT. SOC, XXVIII. (35) AUGUST, 1902. 



