HABITS AND LIFE HISTORIES OF TABANID^. 33 



Female: Palpi light yellow; front wider aliove than below, frontal callosity shining 

 black, almost as wide as the front and with a narrow extension above. Al^domen 

 with three rows of gray spots extending for its whole length; in this sex the gray 

 spots are small but well defined. 



Male: Palpi nearly black, much darker than in the female. The general arrange- 

 ment of colors on the abdomen is the same as in the other sex, but the lateral gray 

 spots are larger. 



Egg-s are placed on stones that project above the water in ritfles of 

 streams. They do not ditier in particular from the eggs of other 

 species of the genus, but the masses observed were not so convex as 

 those of the black horsefly, and being placed on stones of a color simi- 

 lar to themselves are rather difficult to see. Females have been 

 observed ovipositing as early as June S, but most often eggs are 

 deposited after this date. 



Larvae occur in the streams in the fall. In September and October 

 each year we collect the larvte of the dobson fl}' {Coi'ijdaJls cornuta L.) 

 for study in the laborator^^ Whether we obtain these larva3 by turn- 

 ing stones at the edge of swift riffles, or by means of a net stretched 

 across the riffles to catch such specimens as are dislodged by turning 

 stones behind the net in the stream, we find plenty of the larvie of 

 this horsefl}\ I have collected much in streams, but the larva of the 

 river horsefl}^ is the only tabanid larva taken in riffles so far. I have 

 not found it difficult to rear these larv{>?, when taken at the season 

 mentioned, by placing them in damp sand and feeding them on angle- 

 worms. As winter approaches they refuse to eat and take up a posi- 

 tion in the sand and remain quiet until the following spring; then the}" 

 feed actively for a few days and change to the pupa. Like other 

 tabanid larvae the}" are not particular as to their food; all that appears 

 to be necessary is^ that they obtain small, soft-bodied animals. Crus- 

 taceans serve them as well as insects and their own species as well as 

 some other species — whatever, in fact, is in the sand of the breeding- 

 cage. 



Larva (fig. 8, e) , when full grown, about 25 mm. long. General color yellowish 

 white, anterior margin of each thoracic segment and a narrow l^and, including the 

 prolegs, on the anterior half of the first seven abdominal segments opaque, and 

 aijpearing darker than the other parts, which are more or less shining and usually 

 finely striate longitudinally. Prothoracic segment divided by longitudinal grooves 

 into four nearly equal parts, which may be called the dorsal, ventral, and lateral 

 areas. The lateral areas are shining and finely striated on the posterior third and 

 opaque on the anterior two-thirds; the dorsal and ventral areas are opaque on about 

 the anterior fourth and distinctly shining on the remaining parts. The ventral space 

 is plainly divided into two equal parts by a longitudinal groove. In order to see the 

 character of this segment, it must be fully extended. The mesothoracic and metatho- 

 racic segments have a numl>er of longitudinal grooves, some of which are very nar- 

 rowly bordered by opaque darker coloring, which proceeds backward from the narrow 

 anterior border of these segments. Each of the first seven al;)dominal segments has 

 on its anterior part a transverse row of eight tubercles which encircle the segment. 

 These all bear short spines or claws at the apex, excepting a dorsal pair on each of 



