94 NORTH AMERICAN DIPTERA. 



their large, spherical heads. They are not active in flight, 

 and are easily captured. The larvae of this family are para- 

 sitic so far as is known, those of Pipunculus fuscipes having 

 been observed by Boheman in the abdomen of Thamnotettix 

 (Cicadata) virescens. They are elliptical, thick, depressed, 

 narrowed at either end, naked, about three millimeters in 

 length, and somewhat broader in the middle. The puparia 

 are somewhat smaller, oval, obtuse at either end, shining, 

 pitchy black. 



But a single genus, Pipunculus Latreille, is known to in- 

 habit North America. 



3i. PLATYPEZIM:. 



Small, thinly pilose or bare flies, especially characterized 

 by the ornamentation or enlargement of the hind tarsi. Head 

 hemispherical, as broad or broader than the thorax and closely 

 applied to it. Face usually short and broad. Eyes bare, con- 

 tiguous in the male, and in some genera in the female also. 

 Ocelli present. Antennae; porrect, the tirst two joints short, 

 the third somewhat elongate, circular, pear-shaped or conical, 

 with a terminal arista. Scutellum without bristles. Abdo- 

 men comparatively short, the male genitalia projecting in 

 Callomyia only. Legs short and strong; hind legs more or 

 less thickened and the hind metatarsi thickened or variously 

 ornamented, the following joints often partaking in the pecu- 

 liar structure. Wings rather large; third longitudinal vein 

 simple, the fourth sometimes furcate; basal cells small, the 

 anal usually reaching to the margin; discal cell sometimes 

 wanting. 



The flies of this small family are often found dancing in 

 the air in small swarms or running about on the leaves of 

 underbrush. The most remarkable thing connected with 

 them is the extraordinary ornamentation sometimes seen in 

 the hind tarsi of the males, which are always different in 

 structure from those of the females. The flies are not often 



