Rachicerus obscuripennis (Loew 1863)

Rachicerus obscuripennis Loew
1863. Rachicerus obscuripennis Loew, Berl. Ent. Zeitschr., vn, p. 4. 1905. Rhachicerus obscuripennis Aldrich, Cat. N. Am. Dipt., p. 212.
1 Reported from the foot of Pickett Mountain by Johnson (1927: 178). Antennae black, twenty-six to twenty-seven-segmented, strongly pectinate in the male, the processes often paler, somewhat pectinate in female, often reddish towards base of flagellum; front about one-third width of head ; thorax brownish in male to almost blackish in female; abdomen blackish; legs mostly yellowish; wings tinged with grayish, more so in female; female more distinctly marked and darker than male.
Fig. i. Rachicerus obscuripennis Loew, head and antennae. (X 16)
Male. — Length, 6.5 to 8 mm. Head: Vertex, front and face shining black, except the usual silvery pollinose band just above the antennae, the front broadened below so that at its widest point (about two-thirds the distance from the ocellar tubercle to the base of the antennae) it is about one-third the width of the head; palpi yellowish; proboscis black in type, yellowish to reddish in most other specimens I have seen and with short blackish hairs; antennae a little longer than thorax, strongly pectinate below with a long process from each segment (except two basal ones) which is curved at the apex and becomes shorter on the apical segments; twenty-seven-segmented but sometimes apical two or three segments are more or less fused into one; the segments blackish and the processes concolorous, except the basal ones more or less yellowish brown, or sometimes the basal four or five segments and their processes wholly yellowish brown; each segment with black hairs around the apex which are much longer on the two basal segments; the processes with fine pale hairs.
Thorax: Mesonotum subshining, and of a somewhat variable darker or lighter yellowish brown, sometimes with two or three more or less distinct darker stripes; with rather thick somewhat appressed pale hairs, hardly visible except in certain lights; pleura and scutellum yellowish brown, the latter with several darker spots; halteres pale yellowish.
Abdomen: Blackish, subshining, the first and last segments often more or less brownish; above and below with numerous fine appressed pale hairs.
Legs: Pale yellowish, the coxae sometimes tinged with brownish especially the posterior pair; the posterior femora brownish except base or basal half; posterior tibiae brownish at apex, sometimes broadly so; last three tarsal segments more or less brownish.
Wings: Membrane slightly tinged with grayish, broadly and more distinctly so on the apex; veins dark brownish.
Female. — Length, 8 to 12 mm. Differing from the male as follows: antennae pectinate but the processes only about one-half as long as in the male, the third segment wholly and the processes of about two to five of the basal segments of the flagellum reddish; palpi and proboscis usually brownish yellow; thorax darker, usually with two or three blackish stripes; pleura sometimes almost entirely blackish; abdomen, hairs shorter and almost black; legs, coxae wholly and femora except extreme tip blackish, the front femora usually however somewhat more brownish ; otherwise legs much as in male but inclined on the whole to be somewhat darker; wings, darker than in male, tinged with grayish brown.
Type. — The Museum of Comparative Zoology has the following: One male labelled "111. Type Loew, obscuripennis m." in Loew's hand writing; one female labelled " 111. Type Loew" ; three females labelled "Osten Sacken," one of them from Illinois.
Specimens Examined: About 35 males and females.
Maryland: i cf , Plummer's Island, June 29, 1913, (R. C. Shannon), [Shannon];
1 cf, June 29, 1913, (R. C. Shannon); 1 9, July 18, 1916, (R. C. Shannon); 1 9, July 11, 1909, (W. L. McAtee), [all U. S. N. M.]. 1 cf, Cabin John, June 30, 191 1, (Wm. T. Davis), [A. N. M. H.]; 1 d June 25, 1917, (R. M. Fouts), [U. S. N. M.]. 1 cf, Cabin John Run, June 17, 1910, (Wm. T. Davis), [Davis].
Virginia: 2 9 , Great Falls, June 20, (N. Banks), [Pa. Dept. Agr.]; 1 9 , [A. N. S. P.]; 2 cf, 1 9, June 21-29, (N. Banks), [Leonard, ex Banks]; 2 9, June 20 and 21, [A. M. N. H.J; 1 d July 5, 1920, (Bridwell), [U. S. N. M.]; 4 d 3 9, June 27, 1913 and June 29, 1915, (C. T. Greene), [U. S. N. M., Div. Forest Ins.];
2 9, June 27, (N. Banks), [U. S. N. M., ex Aldrich]; 1 9, July 15, 1913, (Wm. T. Davis), [Davis]. 1 cf, Chain Bridge, June 14, (N. Banks), [Daecke]. 1 9, Alexandria County, June 19, 1910, (Wm. T. Davis), [Davis] . 1 cf , Falls Church, July 3, 1916, (J. N. Knull), [U. S. N. M. Div. Forest Ins.].
Indiana: i 9, Lafayette, July 14, 1915, (J. M. Aldrich), [U. S. N. M., ex Aldrich].
Illinois: 1 cf, 1 9 "111.," [M. C. Z.; types]. 1 9, "111.," (Osten Sacken), Michigan:' 2
Missouri: i 9, Atherton, June 20, 1901, [U. S. N. M., ex. Aldrich].
Kansas: i cf , Riley County, July 21, (Kimball), [Kansas]. 3
In addition to the above are two females in the Museum of Comparative Zoology, determined by Osten Sacken, but without locality label; also one female in the Kansas Agricultural College labelled only "No. 5."
Rachicerus sp.
In the United States National Museum is a single specimen
2 Recorded from Detroit by Osten Sacken in Cat. N. Am. Dipt., Ed. 2, p. 42, (1878).
3 Also repotted from Douglas County, by Snow (1903: 212). which undoubtedly represents a new species. It was collected in Los Angeles County, California and is from the Coquillett Collection. Since the end of the abdomen is broken off I am unable to determine its sex but think it is probably a female. The halteres are also lacking. I hesitate to name the specimen but give the following brief description in case a perfect specimen should later turn up.
Length, (only five segments of abdomen present) 6 mm. Wholly shining, brownish, except mesonotum which is blackish and legs which are yellowish; antennae dark brownish, not pectinate and about fifteen or sixteen-segmented ; wings pale brownish.

Rachicerus obscuripennis is a North American Diptera of the Rachicerinae family. It is the only North American species with pectinate (comblike) flagellomeres (antenna segments).