Extracted from: Timberlake P.H., (1962). A Revisional Study of the Bees of the Genus Perdita F. Smith, with Special Reference to the Fauna of the Pacific Coast (Hymenoptera, Apoidea) Part V. University of California Publications in Entomology Editors, Volume 28, No. 1, pp. 1-124.|
The female of this species is distinguished from its closest allies by its entirely dark head, thorax, and abdomen, and by its unusually narrow pterostigma; the male by the scape of its antennae, which is about three times as long as wide.
Female,—Head and thorax dark blue; anterior corners of face, clypeus, supraclypeal area, disk of mesoscutum, and scutellum, black. Mandibles testaceous yellow, becoming red at apex. Abdomen dark fuscous or blackish; pygidial plate testaceous brown. Legs blackish; apex of front femora and anterior side of front tibiae, yellow. Antennae fuscous; flagellum brownish beneath. Tegulae testaceous subhyaline, becoming opaque and dark at base. Wings dusky hyaline, nervures brown, subcosta and margins of stigma fuscous.
Head distinctly broader than long; inner orbits slightly converging below. Proboscis rather short, with galeae two-thirds as long as stipites. Mandibles with a small inner tooth. Facial foveae about their own width from margin of eyes and reaching from upper level of antennal sockets about two-thirds of distance to level of anterior ocellus. Pterostigma slender, between four and five times as long as wide, and about half as wide as first submarginal cell; marginal cell about as long as stigma, with parts beyond and beneath stigma equal in length and longer than wide; second submarginal cell narrowed one-half above and receiving both recurrent nervures. Pygidial plate with apex narrowly blunt or subacute. Head rather weakly tessellate and shining; face closely and minutely punctured, punctures becoming sparser and coarser on clypeus. Thorax mostly polished, except basal area of propodeum, with minute sparse punctures on mesonotum. Pubescence thin, whitish and erect, becoming denser on underside of head and longer and denser on undersurface of thorax. Length: 4.5-5 mm.; anterior wing, 3.2 mm.
Male,—Head and thorax blue-green. Mandibles except red tips, labrum, and all (or nearly all) of face below level of antennae, ivory-white; a narrow line on posterior orbits, nearly to middle of eyes, sometimes expanding at base of mandibles, also more or less distinctly whitish. Lateral face marks extending broadly above level of antennae, obliquely truncate, and ending on orbits close to foveae. Supraclypeal mark with a broad intrusion between antennae and ending acutely on f rons somewhat below level of upper end of lateral marks. Dark color of f rons reaching antennal socket on each side and sometimes intruding between socket and lateral mark to upper end of subantennal plate. Collar of pronotum, large triangular mark on posterior corners of disk, and large mark on tubercles, pale yellow. Abdomen fuscous, more or less tinged with brown, and with a yellow band at base of tergites 2 to 4; band on tergite 2 generally broader than others and that of tergite 5 generally narrow and sometimes obsolete; sometimes a transverse yellow mark on disk of tergite 1. Legs brownish fuscous, apex of femora, front and middle tibiae, front tarsi, middle basitarsi, and underside of hind tibiae, yellow. Antennae fuscous above, more or less brownish toward apex; nagellum broadly yellow or brownish yellow beneath; scape pale yellow or whitish beneath at base, or sometimes with pale color extending entire length. Tegulae and wings as in female.
Head considerably broader than long, with cheeks narrower than eyes; but sometimes greatly enlarged with cheeks very broad and rounded, widest somewhat above middle of eyes. Lateral plates of face in macrocephalous specimens wider than space between them, but in ordinary specimens hardly more than half as wide as space. Disk of clypeus much broader than high, lateral extensions weakly inflexed; in macrocephalous specimens clypeus very strongly transverse. Face below antennae weakly convex from side to side; in macrocephalous specimens nearly evenly depressed except for more prominent supraclypeal area. Facial foveae punctiform but rather large and becoming oval in macrocephalous specimens. Mandibles tapering from base to acute apex and reaching far margin of proboscidial fossa. Antennae moderately long, scape nearly three times as long as thick and somewhat tapering toward base. Flanks of pronotum rather strongly impressed in macrocephalous examples, with posterior corners of disk moderately prominent. Head and thorax polished and shining, except for frons being minutely tessel-late and slightly dullish; punctures on frons extremely minute and indistinct but close, on mesonotum more distinct but sparse. Pubescence thinner than in female but otherwise similar except for hair of face being very short and inconspicuous. Tergite 7 with very narrow and truncate apical lobe. Subgenital plate about twice as long as wide; sides moderately convergent to slightly rounded apex; disk minutely hairy on apical half and on lateral margins. Dorsal lobes of caulis acute, falling short of apex of volsellae, and minutely fimbriate beneath as seen from side; parameral lobes slender in dorsal view and almost hairless; fused part of sagittae thickly fusiform, elongate oval and acute at apex as seen from above, and with tip turned slightly upward in lateral view. Length: 3.5-4.5 mm.; anterior wing, 2.8-3 mm.