Extracted from P. H. Timberlake. 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 Press Berkeley and Los Angeles 1962|
This species and acaciae are the two lightest members of the subfasciata group. The light markings of michelbacheri are more creamy white than yellow, and include a large part of the head and thorax of the male. In the female the abdomen is light with dark bands, although in michelbacheri the bands are so broad and the white intervals on the lateral margins of segments so constricted that the abdomen may appear mainly dark above when much contracted.
Female.—Head and thorax dark green. Mandibles except red tips, clypeus, and small lateral marks between clypeus and anterior end of eyes, creamy white or pale testaceous; disk of clypeus often with two more or less faint brown stripes not reaching dorsal margin. Collar of pronotum and tubercles, white. Abdomen creamy white, with a broad blackish band on tergites 1 to 5, bands on tergites 2 to 4 curving forward on lateral margins and so constricting the white that light bands may appear enclosed when segments are retracted. Legs pale yellow, hind tibiae and tarsi, fuscous. Antennae blackish, scape white except at apex above, flagellum narrowly whitish beneath. Tegulae hyaline, becoming white at base. Wings whitish hyaline, nervures pallid testaceous, margins of stigma and apex of subcosta slightly brownish.
Head as wide as long; inner orbits subparallel. Proboscis moderately long, included within fossa in repose, with apex of galeae reaching base of stipites. Mandibles, reaching about to middle of each other, with a well-developed inner tooth. Facial foveae a little wider than interval between them and eyes and reaching from slightly above level of antennal sockets somewhat more than halfway to level of anterior ocellus. Pterostigma broad and rounded beneath; part of marginal cell beneath stigma nearly one and one-half times as long as part beyond, with metacarpus longer than apical truncation. Pygidial plate somewhat longer than wide at base and narrowed moderately to rounded apex. Head and thorax rather strongly tessellate and moderately dull; punctures fine and rather distinct, sparse on clypeus, rather close-set on sides of face opposite antennae and on mesonotum. Pubescence white, moderately abundant: fine and short on face, rather close-set and subsquamiform on mesonotum, longer and denser on cheeks and underparts of thorax. Length: 4.5-5 mm.; anterior wing, 3.5-3.7 mm.
Male.—Head and thorax creamy white or somewhat tinged with yellow. A large mark across vertex more or less narrowed to summit of eyes and toward occiput, transversely quadrate mark on disk of pronotum, mesoscutum except lateral margins, scutellum, metanotum, dorsal part of propodeum, and orbicular mark on each side of posterior part of mesopectus, dark green. Abdo¬men whitish; a brownish or fuscous band at apex of tergites 1 to 5 or 6 either abbreviated or reaching lateral margins (on tergite 1 sometimes covering most of dorsal surface of segment). Legs yellowish white, a spot at apex of hind femora, outer margin of hind tibiae and basitarsi, and four apical joints of hind tarsi, brown or pale fuscous; sometimes a dark line on middle tibiae. Tegulae and wings much as in female, but subcosta and margins of stigma more brownish.
Head as broad as long; cheeks very broad and widest opposite middle of eyes. Mandibles tapering, very acute at apex, and reaching for margin of proboscidial fossa or beyond. Facial foveae oval, twice as long as wide. Face below antennae strongly convex from side to side; subantennal plates small and oblique. Antennae rather short; scape oviform, about twice as long as wide and narrowed toward base; flagellum nodose beneath, with joints, except apical four, slightly wider than long. Pronotum normal, flanks only slightly impressed. Head and thorax finely tessellate, slightly dullish, almost impunctate; tessellation distinct only on green parts. Pubescence whitish, thinner than in female but subsquamif orm on mesonotum; face nude, cheeks nearly nude, but underside of head with dense hair increasing gradually in length posteriorly. Tergite 7 with apical lobe truncate and wider than long. Subgenital plate somewhat longer than wide, sides slightly converging to rounded apex, apical half of disk with very finepubescence. Dorsal lobes of caulis very acute, with volsellae well exposed in dorsal view; parameral lobes more dilated toward apex than in allied species and with a long but thin fringe of hair; sagittae with fused apical part very broad but longer than wide as seen from above, somewhat narrowed to apex, and in lateral view moderately thiek and fusiform. Length: 3.5-4.5 mm.; anterior wing, 2.8-3.2 mm.