April, 1910.] 
Four Genera oj Horseflies. 
149 
A COMPARATIVE STUDY OF FOUR GENERA OF HORSEFLIES 
James S. Hixe. 
The dipterous family Tabanidae contains a number of genera 
which are not well known on account of the scarcitv of material 
in the museums of the country. A group of four American genera 
which are nearly related in some respects and which have not 
been studied in a comparative wav are known as Lepidoselaga, 
Selasoma, Bolbodimyia and Snowiellus. As I have the tvpical 
species of all of these genera I have selected about a dozen points 
upon which to make comparison and a brief statement of the 
results is offered for the purpose of extending acquaintance with 
these rather extraordinary members of our American fauna. 
1. Female of Snowiellus atratus, enlarged two diameters; 2, side 
view of the head of Lepidoselaga lepidota : 3, same of Selasoma tibiale; 
4, same of Bolbodimyia bicolor: 5, same of Snowiellus atratus. 
The species of all these genera agree in having the wings 
largely black, the body wholly black, subcalius denuded, pro- 
boscis short and fleshy, third segment of the antenna composed 
of five annuli of which the basal is plainly longer than the others 
taken together, anterior tibia distinctly enlarged, hind tibia 
ciliate and the anal cell closed and petiolate. Although there 
are several characters common to all many differences exist and 
these are best pointed out by considering each genus separatelv. 
Lepidoselaga. Type species L. lepidota from Central and 
South America. Length about seven millimeters, bodv shining 
black with sparse green-reflecting scale-like hairs. The genus 
was first called Lepiselaga by Macquart in 1838 and later emend- 
ed by Loew, according to Osten Sacken. Hadrus of Perty, 
