AMERICAN DIPTERA. 385 



SYNOPSIS OF SPECIES.* 



1. Third and fourth abdominal segments wholly black 3. 



Third and fourth abdominal segments largely or wholly red 2. 



2. Body red, a black spot on the second abdominal segment. ...riif lis. 

 Body black, abdominal segments 3-6 largely red....jibrtoiniiialis. 



3. Antennal style one-half as long as the third segment 4. 



Antennal style only one-fourth as long as the slender third seg- 

 ment; Eastern species pictiis. 



4. Fifth abdominal segment in the male more than three times as 



wide as long 5 . 



Fifth abdomenal segment in the male less than three times as 

 wide as long; California species 6. 



5. Inhabits the Atlantic States politus. 



Inhabits California dives. 



6. Brown spot at tip of wing not crossing the first and second poster- 



ior cells; hind tibiae and tarsi of the male densely silvery 



within arg'eutatiis. 



Brown spot at tip of wing crosses the first and second posterior 

 cells; hind tibiae and tarsi of the male not silvery. 



seinulator. 

 Nicocles abcloininalis. 



Nicocles abdominaUs Williston, Trans. Am. Ent. Soc, XI, 17, 



PI. I, figs. 14, 14a, 14b, 1884. 



"S'. — Length 11-12 mm. — Black, moderately polished; the third, 



fourth, fifth and sixth abdominal segments, except the narrow lateral 



margins, yellowish-red; fifth segment about four times broader than 



long. Wings variegated with dark brown. 



"Head much broader than high, much flattened, the face scarcely 

 more than one-fourth the entire width, the inner margins of the eyes 

 nearly parallel throughout. Face flattened, but very slightly project- 

 ing in profile below, black, somewhat polished, whitish dusted below, 

 a row of brown bristles along the oral margin, intermixed with sparse 

 long whitish pile, which extends upon the face nearly to the antennas. 

 Front more opaque black; the bristles on the ocellar tubercle brown 

 or blackish. Antennas black; the first two segments with blackish 

 hairs; first segment a little longer than the second, the latter short; 

 third segment nearly twice as long as the first two combined, slender, 

 of nearly equal width throughout; style divergent, rather slender, 

 acuminate, less than half as long as the third segment, terminating in 

 a microscopic bristle. Occipito-orbital bristles brown; pile below soft, 

 white, rather long and abundant. Dorsum of thorax black, with two 

 broad, velvety opaque black stripes, narrowly separated by a slightly 



* As I have had very little material in this genus for study, I am 

 using Mr. D. W. Coquillett's key, partially modified, which appeared 

 an the Canadian Entomologist, vol. XXV, 119; 1893. 



TRANS. AM. ENT. SOC, XXXV. (49) SEPTEMBER, 1909 



