Description of
Nebritus tanneri (Hardy)
(Diptera: Therevidae: Therevinae)

Zionea tanneri Hardy (1938:144); Cole (1965:349); Irwin and Lyneborg (1981a:249). Type locality: Zion National Park, Utah.

Nebritus tanneri (Hardy); Irwin and Lyneborg (1981a:249).

Derivation of name.This species was named in honor of Dr. V. M. Tanner.

Diagnosis. Males and females of Nebritus tanneri are very similar to N. powelli in having the scape cylindrical, dark reddish brown, gray pruinose; the length of the scape less than 0.80 mm; the length/width ratio of the scape greater than 3.5. Unlike Nebritus powelli, N. tanneri has scattered, dark reddish brown setae on the median area of thorax; a lateral patch of gold setae on the scutellum; and sternite 8 in males is broad, bilobed; the gonocoxite has a distinctive posteromedial patch of black setae as seen in ventral view; and the ejaculatory apodeme is broadly expanded anteriorly.

Description of holotype female
(MEI 007000). Body length 6.5 mm.

Head. Length 1.0 mm. Ocellar tubercle dark reddish brown, glossy; ocellar setae dark yellow, elongate, scattered. Eye reddish brown; median margin sinuate. Frons (Fig. 29) pollinose on dorsal two-thirds, ventral third dark reddish brown, glossy; a black pruinose area exists dorsolaterally and silver pile extends laterally from antennal bases to margin of eyes; setae variable, gold, elongate, scattered over pollinose area and dark reddish brown on dark reddish brown area of frons. Antenna (Fig. 30). Dark brown, gray pruinose; setae dark brown, scattered over scape and pedicel and basally on flagellum; macrosetae dark brown, scattered on scape; length of antenna 1.2 times head length; scape cylindrical, elongate, length 0.62 mm, 5.2 times width, 7.8 times length of pedicel; length of pedicel 0.08 mm, 0.7 times width; length of flagellum 0.54 mm, 4.5 times width, 0.9 times length of scape; style length 0.04 mm. Parafacial pollinose, median and tentorial pit areas dark reddish brown, glossy. Genal setae white. Maxillary palp dark yellow; length 0.52 mm, 5.2 times width; setae dark yellow.

Thorax. Macrosetae: np 3, sa 2, pa 1, dc 1, sc 2. Dark brown, gray pruinose; setae dark brown, fine, scattered with a broad lateral band of gold lanceolate setae; vittae dark brown, dorsocentral and dorsolateral vittae separated by broad yellowish brown pruinose stripe. Postpronotal lobe concolorous with thorax; setae gold, lanceolate. Prosternal setae white. Pleuron dark brown, dense gray pruinose; setae white, elongate, abundant on propleuron, scattered over entire anepisternum and katepisternum. Scutellum dark brown; setae pale yellow, dense laterally. Laterotergite dark brown, dense gray pruinose; setae white.

Wing. Length 4.5 mm, 2.6 times width; pale brown, concolorous, costal cell darker; pterostigma dark brown. Halter brown, stalk pale yellow.

Legs. Coxae dark brown, dense gray pruinose, apical macrosetae dark reddish brown. Fore and middle femora dark reddish brown, gray pruinose, apical fourth dark yellow; hind femur dark yellow; setal pattern a mixture of scattered, white, and dark brown, elongate setae and white, appressed, lanceolate setae, hind femur lacks white, elongate setae. Tibiae dark yellow, apex reddish brown; tarsomere 1 dark yellow, apex dark reddish brown; tarsomeres 2-5 dark brown.

Abdomen. Dark brown, gray pruinose; lateral margins dense gray pruinose; dorsal setae dark yellow, subappressed; lateral setae white, fine.

Terminalia as in Figures 37-38. Furca, as in Figure 38, oblong; posterior margin truncate; anterior margin broadly rounded; lateral margins parallel.

Variation. Body measurements given in table.Thorax. Macrosetae: np 2-4, 3, sa 2-3, 2, pa 1, dc 1, sc 2.

Description of Male.
Similar to female with following exceptions. Body measurements given in table.

Head. Frons (Fig. 29) with mixture of dark yellow and dark brown setae on pruinose area, black setae on dark reddish brown area.

Thorax. Macrosetae: np 3-4, 4, sa 1-2, pa 1, dc 1 sc 2. Gold setae across anterior margin of mesonotum.

Legs. Tibiae and tarsi dark reddish brown.

Abdomen. Terminalia (Fig. 31-36). Tergite 8 broad, bilobed. Sternite 8 bilobed, constricted medially. Gonocoxite with distinct posteromedian patch of black setae in ventral view . Ejaculatory apodeme broadly expanded anteriorly.

Immature Stages. Unknown.

Seasonal Activity. In the specimens examined, adults were collected from 11 April to 27 July. Adults have been collected on Pinus monophylla, on dunes and sandy creek bottoms, and in Malaise traps.

Distribution. Nebritus tanneri ranges from Baja California Norte to north-central California, and eastward to western Nevada and southwestern Utah. (Map)

text from Webb & Irwin 1991a

[ Nebritus tanneri index | Begin key to Nebritus ]