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.|
P. exilis resembles austini in many ways, but the male has much more yellow on the head and thorax, the legs almost entirely yellow, and the abdomen orange yellow. The female's head and thorax are entirely dark and shining, and the abdomen ferruginous. This species lives in the deserts of southern California and collects pollen from the flowers of Petalonyx thurberi.
Female.—Head and thorax bluish green, without light markings; clypeus, anterior corners of face, supraclypeal area, disk of mesoscutum, and scutellum, almost black. Abdomen reddish ferruginous, base of tergite 1 more or less infuscated, apical part of tergites 3 or 4 and 5 a little dusky, pygidial plate concolorous. Legs blackish or tinged with brown, front tibiae and tarsi yellow. Antennae fuscous, flagellum more brownish beneath, scape testaceous at base. Labrum and proboscis brown, galeae and glossa testaceous. Mandibles ferruginous, a little dusky at base and red at apex. Base of tegulae fuscous, outer margin broadly subhyaline. Wings clear hyaline, nervures pale testaceous, subcosta and margins of stigma brown.
Form slender. Head barely longer than wide; clypeus strongly projecting, convex, prominent, and apex of disk truncate. Facial foveae well impressed, about their own width from margin of eyes and reaching from level of upper margin of antennal sockets about two-thirds of distanceto level of anterior ocellus. Mandibles rather stout, acute at apex, with a small inner tooth, and reaching approximately to far margin of proboscidial fossa. Proboscis of moderate length, apex of galeae falling slightly short of base of stipites when folded in repose. Pterostigma about three times as long as wide and about three-fourths as wide as first submarginal cell; marginal cell shorter than stigma, with part beneath stigma generally longer than part beyond, and apical truncation equaling or slightly greater than the metacarpus. Pygidial plate longer than wide, with moderately wide rounded apex. Head and thorax impunctate, shining, very weakly tessellate, with tessellation almost obsolete on disk of mesoscutum and scutellum. Face, mesonotum, metanotum, and propodeum, nude; sides of thorax almost nude; cheeks with sparse, short, erect whitish hair; front coxae and mesopectus with comparatively long dense hair. Length: about 3.6-4.2 mm.; anterior wing, 2.8-2.9 mm.
Male.—Head and thorax bluish green. Anterior half of underside of head, cheeks generally to above middle of eyes, mouth-parts except red tips of mandibles, labrum, and face to level of foveae, clear lemon yellow. Upper margins of yellow on face usually bisecting foveae but uneven and notching the green in median line, with the green forming a broad lobe on each side of middle and sometimes sending a narrow streak to antennal sockets. Prothorax, including sternum, yellow; but notum with a dark band from flank to flank. A broad-limbed, yellow T-mark on mesosternum, with outer ends of arms narrowed and somewhat deflected backward. Lower margins of flanks of propodeum sometimes broadly yellow, or with two yellow spots. Abdomen orange yellow, basal half of tergite 1 more or less dusky or infuscated. Legs yellow, outer margins of hind tibiae and tarsi tinged with brown. Antennae yellow, pedicel and flagellum pale brown above. Tegulae and wings as in female, except base of tegulae definitely yellow.
Head usually rather small, a little longer than wide, with cheeks rounded beneath; but sometimes enlarged and quadrate, with broad cheeks obtusely angled anteriorly. Clypeus rather small with disk somewhat broader than high, moderately convex with lateral extension not greatly reflexed and visible in frontal aspect. Mandibles with a subquadrate expansion on outer margin at base, tapering and acute at apex, and reaching slightly beyond far margin of proboscidial fossa. Facial foveae oval, about twice as long as wide. Occiput shallowly concave, with width of concavity distinctly less than width of space between summit of eyes. Flanks of pronotum only moderately impressed even in the most macrocephalous examples. Sculpture about as in female, but tessellation on frons and mesonotum slightly more evident. Undersurface of head, front coxae, and mesosternum with thin, rather short, white hair; cheeks, mesopleura, and anterior part of mesoscutum with very sparse short hair; head and thorax otherwise virtually nude. Sides of tergite 7 converging to moderately narrow and rounded apical lobe. Subgenital plate about twice as long as wide, moderately tapering to rounded apex, and with fine short hair on apical part of disk. Caulis of aedeagus as broad as long; dorsal lobes somewhat divergent, obtusely angled at apex in dorsal view and rounded in lateral view; volsellae very unequal, inner or ventral pair slightly surpassing dorsal lobes of caulis; parameral lobes slender as seen from above and clavate in lateral view; sagittae elongate fusiform, widest about one-fourth of length from apex, thickest dorsoventrally near middle, and with apex very acute in both dorsal and lateral views. Length: 2.5-3 mm.; anterior wing, 2.3-2.5 mm.