Perdita (Xerophasma) Cockerell

Griswold, Terry & Miller, Wensdae, 2010, A Revision of Perdita (Xerophasma) Timberlake (Hymenoptera: Andrenidae), Zootaxa 2517 (1), pp. 1-14 : 3-4

Perdita (Xerophasma) Cockerell

Xerophasma Cockerell 1923: 1 . Type species: Xerophasma bequaerti Cockerell 1923 .

Diagnosis. Xerophasma can be distinguished from all other subgenera of Perdita by the enlarged ocelli (each about 1/5 to 1/3 width of interocular distance at level of median ocellus) and from all except some members of the subgenus Alloperdita Viereck , (restricted to the eastern United States) by the small triangular, petiolate submarginal cell intercalated between the two submarginal cells normal for Perdita . This third submarginal cell is likely a derived character not homologous to the second submarginal cell found in many Andrenidae ( Michener 2007) . It is unclear whether it is a synapomorphy for the two subgenera ( Danforth 1996, Michener 2007). In Xerophasma , the body color is largely pale caramel-colored, with extensive dark markings on the head and mesosoma in some species, and all species have some degree of light to dark brown tergal banding.

Description. Female. Length: 6.5–11.5 mm; forewing length: 4.5–8.3 mm. Body off-white to caramelcolored except dark brown pygidial plate and tergal bands and sometimes on face and mesosoma. Pubescence white, fine, mostly short and inconspicuous except long on gena, legs, mesepisternum. Sculpture finely reticulate, shallow on anterior third of mesoscutum. Head slightly wider than long, no wider than mesosoma. Mandible slender, tapering to acute apex (except with subapical tooth in P. celadona ), base pale caramelcolored, apex brown. Inner eye orbits parallel to slightly convergent below. Antenna long, slender, with length of flagellomeres equal to or greater than their width. Facial fovea shallowly impressed, dull, linear or elliptical, darker than rest of face. Ocelli enlarged, median ocellar diameter 1/5 to 1/3 width of interocular distance at level of median ocellus. Gena in lateral view about ½ as wide as eye (except as wide in P. rhondae ), widest above middle of eye. Tibial spurs long, straight, slender, tarsal claws with medial tooth. Scopal hairs of hindtibia long, straight, rather sparse, hair on outer side of hindbasitarsus shorter but otherwise similar. Forewing extending to or beyond apex of metasoma. Stigma large, width equal to or slightly broader than first submarginal cell. Marginal cell as long as stigma but not quite reaching halfway to apex of wing. Small triangular, petiolate intercalary submarginal cell almost always present between the normal first and second. Wings hyaline, veins and stigma light brown, except subcostal vein dark brown. Branched hairs surrounding pygidial plate, long hairs on gena and mesepisternum. Pygidial plate acutely angled.

Male. Length: 5.5–10.5 mm. Forewing length: 4.0– 7.1 mm. Similar to female except body sometimes darker colored, gena slightly wider in lateral view; tarsal claws bifid, pygidial plate absent.

Variation. Occasional specimens of P. vespertina and P. celadona are missing the petiolate intercalated submarginal cell on one or both wings. Such specimens of P. vespertina from Riverside, Nevada, May 1983 are as follows: 3 females and 1 male missing on left wing only, 1 female incomplete on right wing only, 2 females with incomplete right and missing left, 1 female incomplete left, 4 males missing cell on both wings. One P. vespertina male from Mesquite, Nevada 1998 is missing the third submarginal cell on both wings .

Distribution. Previously known only from the Sonoran and Chihuahuan Deserts ( Timberlake, 1953, 1954, 1958), Xerophasma is now known to occur in the Colorado Plateau and the Mojave Desert and on the western margin of the Great Plains ( Figs. 26–28 ). All Xerophasma are crepuscular visitors to Onagraceae of the genera Camissonia and Oenothera in desert and semi-desert regions of southwestern North America. They are frequently found associated with sand dunes and vegetated sands.

Figures

FIGURES 26–28. Distributions of Perdita (Xerophasma) in the southwestern United States and adjacent Mexico. Perdita celadona (26), P. vespertina (27), P. rhondae (), P. pallida (), and P. bequaertiana () (28). Bar equals 100 km.