232 American Midland Naturalist Monograph No. 3 



slightly elevated, each bearing several weak setae. Tenth sternite (X-S) lightly 

 sclerotized. Phallosome (Ph) small, narrowest near base, open dorsally and 

 ventrally, consisting of two heavily sclerotized plates bearing strong teeth api- 

 cally. Claspette stem (Cl-S) stout, pilose, capitate, fused to basistyle and 

 crowned with numerous short setae; claspette filament absent. Basistyle (Bs) 

 about three times as long as basal width, curved, becoming narrower beyond 

 basal third, rounded at apex, clothed with scales and long setae (setae more 

 numerous on outer aspects and along inner ventral margin) ; basal and apical 

 lobes absent. Dististyle (Ds) broad, flattened, about two-thirds as long as 

 basistyle, with tip densely pilose and bluntly pointed; claw (Ds-C) stout, 

 borne on a small thumb-like projection at apical fifth of dististyle. 



larva. (Fig. 128). — Head broader than long. Antenna half as long as 

 head, curved, spinose; antennal tuft multiple, inserted near middle of shaft, 

 nearly reaching tip. Head hairs: Preantennal (A) multiple, reaching beyond 

 insertion of antennal tuft; lower (B) 2 to 3-branched; upper (C) 3 to 5- 

 branched (hairs A, B, and C not inserted in a straight line) ; postclypeal (d) 

 small, multiple; sutural (e) single; trans-sutural (f) and supraorbital single 

 or double. Upper lateral abdominal hairs double or triple on segments I to 

 V. Comb of eighth segment of about 9 to 12 thorn-shaped scales in an irregu- 

 lar single or double row; individual scale with a long apical spine and short 

 lateral spinules. Siphon about three to three and one-half times as long as wide; 

 pecten reaching to middle of the siphon or beyond, with the last two or three 

 teeth somewhat longer and widely spaced; subventral tuft small, multiple, in- 

 serted beyond pecten. Anal segment longer than wide, with dorsal plate extend- 

 ing ventrally nearly to mid-line; lateral hair single; dorsal brush consisting of a 

 long lower caudal hair and a shorter upper caudal tuft of 4 or 5 branches on 

 either side; ventral brush large, with 4 or 5 smaller tufts preceding the barred 

 area; gills 4, longer than the segment. 



distribution. — A widespread species occurring throughout the Palearctic, 

 Nearctic and Oriental regions. It is common in southern Canada and through- 

 out most of the United States, but less abundant in the extreme South. South- 

 ern States: Alabama (170); Arkansas (30); Florida and Georgia (52); 

 Kentucky (140); Louisiana and Mississippi (52); Missouri (1); North Caro- 

 lina (166); South Carolina (64); Tennessee (170); Virginia (49). Other 

 States: Arizona, California, Colorado and Connecticut (52); Delaware (106); 

 District of Columbia, Idaho, Illinois and Indiana (52); Iowa (155, 156); 

 Kansas (79); Maine (137); Maryland and Massachusetts (52); Michigan 

 (88); Minnesota and Montana (52); Nebraska (178); New Hampshire, New 

 Jersey, New Mexico, New York, North Dakota and Ohio (52); Oklahoma 

 (159); Pennsylvania (8); Rhode Island (99); South Dakota (129); Texas 

 (108); Utah (142); Vermont (90); West Virginia (52); Wisconsin (48); 

 Wyoming (129). 



bionomics. — The females are troublesome biters, feeding in shady places 

 during the day and becoming especially annoying at dusk and after dark. 

 Adults are able to migrate long distances from their breeding places. Rees 

 (142) found that this species has a flight range of 5 to 8 miles in Utah, while 

 Hearle (78) claims that in British Columbia it can migrate a distance of ten 

 miles with ease. The larvae occur in rain-filled depressions and flood waters. 



