Geron elachys Hall & Evenhuis

Hall, Jack C. & Evenhuis, Neal L., 2003, Review of the subgenus Geron (Geron) Meigen in the Nearctic Region (Diptera: Bombyliidae: Toxophorinae), Zootaxa 181, pp. 1-72 : 27-28

Geron elachys Hall & Evenhuis , sp. nov.

Description. Male. Head. Small species, 2–5 mm in length. Front silvery tomentose, hair wanting; antenna black; scape with short white hair; pedicel with shorter and less white hair; first flagellomere parallel sided from base to near midpoint, then tapering to acuminate apex; antennal ratio: 7:3:14; face cinereous pollinose, white pilose, bare medially; silvery tomentum lateral to antennal base; oral margin pale; proboscis projects beyond oral margin for a distance approximately one and one­half times head height; gena and occiput white pilose and tomentose, occipital tomentum confined to lower half of occiput; ocellar tubercle with dark (not black) hair.

Thorax. Mesonotum dull black; side and anterior margin slightly cinereous pollinose; median longitudinal stripe vague, narrow, extending beyond transverse suture; notum white pilose, tomentum wanting; pleura white pilose and tomentose; legs black with white hair and scales; halter with stem and knob white; scutellum white pilose, tomentum wanting.

Wing. Hyaline; venation normal; crossvein r­m at middle of cell dm; crossvein m­cu at most only slightly curved; basicosta with white hair.

Abdomen. White pilose, dorsum with scattered pale yellow tomentum, white tomentum elsewhere; tergites with lateral margins narrowly pale; sternites with posterior margins narrowly pale.

Genitalia ( Fig. 37 ) with gonocoxa in ventral view flat without depressions or ridges; gonocoxa in lateral view rectangular, about two times longer than high; gonostylus normal, broadly rounded apically; lateral ramus narrow, narrowly rounded apically, nearly coextensive with gonostylus; dorsolateral ramus short, stub­like aedeagus short.

Female. As in male except as follows: Head. Eyes at vertex separated by approximately one and one­half times width of ocellar tubercle; front with white hair and silvery white scales; occiput with silvery white scales. Thorax. Mesonotum and abdomen white pilose and tomentose, however, that on abdomen often yellow; fore tarsi with palynophilic setae. Genitalia with posterior projection of tergite VIII black; vaginal furca ( Fig. 8 ) simple, upper half narrowly V­shaped; lower half with slender arms straight, then bent slightly inward on apical third, apex not swollen.

Types. Holotype male and allotype (Indian Ranch, Panamint Valley, Inyo County , California, 29.iv.1975, J.C. Hall) on Prosopis . Paratypes. California. Inyo County : 7, topotypic, taken with types; 8, Warm Sulphur Springs, 15.viii.1985 (J.C. Hall); 7, 13 mi. N Shoshone, 29.viii.1979 (J.C. Hall & N.L. Evenhuis). San Bernardino County: 3, 3 mi. N. Hinckley, 13.x.1982 (J.C. Hall); 2, Mesquite Springs, 12.iv.1984, 25.v.1982 (J.C. Hall, J. LaSalle). Los Angeles County: 1, 3 mi N. Lancaster (P.H. Timberlake); 7, 2.3 mi. E Little Rock, 13.ix.1950 (P.H. Timberlake), San Diego County: 1, Borrego Valley, 18.iv.1957 (J.C. Hall). Imperial County: 1, Salton Sea Beach, 30.iv.1953 (J.C. Hall). Arizona. Carrizo Creek, 18.vi.1950 (P.P. Cook). Nevada. Nye County: 1, 9 mi. N Warm Springs, 7.vii.1980 (J.C. Hall). Holotype and allotype deposited in USNM. Paratypes deposited in USNM and UCR.

Variation. This species is one of the few that expresses little variation. The tomentum on the female varies from pale yellow to yellow. The vaginal furca varies slightly depending upon the degree of sclerotization.

Discussion. Geron elachys , sp. nov. is very similar to G. prosopidis , sp. nov.; the two are often taken together. The configuration of the genitalia of both sexes amply separates the two species. Geron elachys is frequently taken on flowers of Heliotropium curvassavicum . This is one of the few species that has the legs entirely black.

Biology. Immature stages unknown. Adults have been taken at flowers of Prosopis sp., Heliotropium curvassavicum , Chrysothamnus sp., and Gutierrezia lucida .

Distribution. United States (Arizona, California, Nevada).

Etymology. The specific epithet derives from the Greek “ ” = small; referring to the relatively small size of this species as compared to most species in this region.

Figures

FIGURES 34 – 37. Geron male genitalia. 34, G. borealis Hall & Evenhuis, sp. nov.; a, lateral view; b, tip of gonocoxa, ventral view. 35, G. confusus Hall & Evenhuis, sp. nov.; a, lateral view; b, tip of gonocoxa, ventral view. 36, G. cressoni Hall & Evenhuis, sp. nov.; a, lateral view; b, tip of gonocoxa, ventral view. 37, G. elachys Hall & Evenhuis, sp. nov.; a, lateral view; b, gonocoxa, ventral view.

FIGURES 7 – 12. Geron vaginal furcae. 7, G. cressoni Hall & Evenhuis, sp. nov. 8, G. elachys Hall & Evenhuis, sp. nov. 9, G. eriogonae Hall & Evenhuis, sp. nov. 10, G. halli Evenhuis, sp. nov. 11, G. holosericeus Walker. 12, G. infrequens Hall & Evenhuis, sp. nov.