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.... rufus. 

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



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 pictus. 



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 (lives. 



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 argentatus. 



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



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



semulator. 

 Nicocles abdominalis. 



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



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

 "cT- — 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. Antennae 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 



