Species account taken from "A Revision of Perdita (Xerophasma) Timberlake (Hymenoptera: Andrenidae) Authors: TERRY GRISWOLD & WENSDAE MILLER Source: Zootaxa, Vol 2517 (June 24, 2010) pp. 1-14"
Perdita pallida Timberlake 1954:349. Holotype female, Hopkins Well, Riverside Co., California. (San Francisco) (examined).
Female. Length: 7.5–9.5 mm. Forewing length: 5.4–6.7 mm. Head, mesosoma, legs entirely pale caramel-colored, except: face cream-colored; facial fovea dark golden brown; fine dark line sometimes present on vertex medially between lateral ocelli. Costal vein dark, prestigma light, stigma evenly stained, without dark margins. Terga pale caramel-colored except light brown subapical bands on T1–4. Frons, mesoscutum, scutellum shiny; propodeal triangle dull with finely carinulate triangular area basally. Mesoscutum moderately densely punctate, covered with moderately dense hair. Forecoxa, mesepisternum with long apically straight hair, sparse on forecoxa, dense on mesepisternum.
Mandible simple, without preapical tooth. Labrum with apical margin obtusely angled. Clypeal width dorsally equal to or slightly greater than width of each subantennal area. Frontal line strongly raised halfway to median ocellus then strongly depressed to median ocellus. Facial fovea sparsely pubescent, linear, shiny to dull, extending from ventral margin of median ocellus to middle of antennal socket. Ocellar area inflated. Median ocellar diameter 1/4 interocular distance at level of median ocellus. Length of vertex behind lateral ocellus less than ocellar diameter. Forecoxa with long, erect, slightly plumose, straight hair; mesepisternum ventrally with short, obliquely directed, straight hair. Length of marginal cell on wing margin twice apical width. Pygidial plate narrowly to broadly rounded.
Male. Length: 8.0–8.5 mm. Forewing length: 5.2–5.7 mm. Head, mesosoma, legs pale caramel-colored except: entire head slightly yellow; golden antenna; light brown integumental line on vertex medially between lateral ocelli; dark brown facial fovea, terga without preapical bands except sometimes quadrate brown mark on T1. T2 lateral fovea forming fine undarkened line. Sculpture, punctation, pubescence as in female.
Clypeus dorsally as wide as subantennal area. Supraclypeal area not protuberant, without tuft of hair. Facial fovea tear-shaped, extending half distance from ventral margin of median ocellus to dorsal margin of antennal socket, indistinct ridge defining fovea. Frontal line, ocellar diameter, forewing as in female. T7 with pygidial plate ill-defined, without apical tuft of hair protruding from beneath apical margin. S8 as in Fig. 17. Genitalia as in Figs. 7, 12.
Diagnosis. Perdita pallida can be distinguished from all other P. (Xerophasma) except P. bequaertiana by the entirely pale integument. It differs from P. bequaertiana by the smaller ocelli. Females further differ in the presence of very short hair on the facial fovea and the greater postocellar distance on the vertex; males in the cream to pale yellow frons and the shape of S8.
New material. MEXICO SONORA: El Golfo, 6 mi N, 10 Apr 1975, M. Wasbauer. USA NEVADA Clark County: 2 females, 2 males, 0.4 mi E St. Thomas Gap, 11S E760620 N4032979, 12 May 2005, fluorescent blue pantrap, D. Allen, E. Ahlstrom, R. Andrus, S. Higbee; 2 males, 1 female, same except fluorescent yellow pantrap; 2 males, same except white pantrap; 4 males, 3 females, same except 25 May 2005, fluorescent yellow pantrap, E. Ahlstrom, S. Higbee; 1 male, 1 female, same except 25 May 2005, white pantrap, E. Ahlstrom, S. Higbee; 1 female, same except 20 May 2004, fluorescent blue pantrap, S. Higbee, E. Ahlstrom, D. Skandilis, L. Saul; 1 male, same except fluorescent yellow pantrap; 1 male, white pantrap; CALIFORNIA Imperial County: 1 male, 23 females, Algodones Dunes, 3.5 mi SE Glamis, 28 Apr 1978, at light, A. Hardy, F. Andrews; 1 female, Algodones Dunes, 9.5 mi NW Glamis, Site 37, 32°4'27"N 115°12'45"W, 19 Apr 1979; 1 female, Algodones Dunes, S Ruthven, 32°55'30"N 114°59'34"W, 6 Apr 2000, at light, D. Yanega; Riverside County: 1 female, Blythe, 22 May 1969, at light, J. Johnson, R. Gill; San Bernardino County: 2 males, 1 female, Kelso Dunes, Mojave National Park, 770m, 34°35'20"N 115°43'02W, 19 May 2001, Oenothera, D. Yanega; 1 male, 1 female, Palen Dunes, 27 Apr 1978, at light, F. G. Andrews, A. R. Hardy; 2 males, Parker Dam, dunes SW, 150m, 34° 155’N 114°08’W, 8 Apr 2005, L. Packer. New records are from the following institutions: Riverside, Sacramento, Davis, and Toronto.
Range. Northwestern Sonoran Desert and eastern Mojave Desert in California and adjacent Nevada (Fig. 28).
Variation. Two females in poor condition from north of the known range of P. pallida (California, San Bernardino Co., near Saratoga Springs; Davis collection) may represent this species. They differ by the presence of dark markings on the head. These include a stripe above the antennal socket connected with markings in the interocellar region, and markings on the vertex behind the eye.