Extracted from: Timberlake P.H., (1969). A Contribution to the Systematics of North America Species of Synhalonia (Hymenoptera, Apoidea). University of California Publications in Entomology Volume 57|
This species is most similar to aceroa and is distinguished from all other species in that the female has long, antrorse, ferruginous hair on the blades of the maxillae. It is now very common in California at flowers of Amsinckia and was probably increased enormously in population during the present century, as Amsinckia has become a vernal weed in disturbed soils and cultivated fields.
Female.óBlack; legs more piceous; apical joints of tarsi brown. Pubescence ochreous, paler on face and beneath, and rather long and dense on thorax. Hair of tergite 1 of abdomen long and whitish, and that of following segments mostly very short and black; tergite 4 with an apical white band, and on each side of tergites 2 and 3 a white spot; disk of tergite 2 with thin, short, erect whitish hair, but apical depression with black hair forming a band, broad at middle and narrowed to the white spot on each side; hair of tergites 5 and 6 black, with apical band of tergite 5 white interrupted with brown at middle. Hair at base of sternites black, but long apical fringes white, that on sternite 5 brown in middle. Hair of legs white, but ferruginous on inner side of basitarsi, pale brown on outer side of front and middle tibiae, and chocolate brown on dense tuft at apex of hind femora and hind basitarsi. Tegulae clear amber, fuscous at base. Wings dusky hyaline, nervures piceous, subcosta black.
Head much broader than long, inner orbits parallel, vertex only slightly impressed on each side. Lateral ocelli their distance apart from nearest eye. Proboscis long, galeae long, taper¨ing, and clothed with long, antrorse, pale ferruginous hair. Clypeus rather finely rugoso-punctate; head otherwise and thorax very finely shagreened, subopaque, mesonotum with close, obscure punctures. Second submarginal cell receiving recurrent nervure about one-fifth of its length from apex. Pygidial plate moderately wide and rounded at apex. Length 11-13 mm, anterior wing 8-8.5 mm, width of abdomen 4.3-4.8 mm.
Male.óBlack, tarsal claw ferruginous, tibial spurs pale testaceous. Labrum and clypeus, except on lateral margins, yellow; clypeal mark moderately well separated from margin of eyes, much broader than high, broadly truncate at summit, and usually very obtusely emar-ginate on each side. Pubescence rich fulvo-ochraceous, varying to pale ochraceous, and paler beneath, and dense on cheeks and thorax. Hair at base of abdomen, including basal half or more of tergite 2 pale fulvous or ochraeeous, varying to whitish, and black beyond, becoming more or less whitish across apex of tergite 6 and sometimes with small patch of light hair on apex of tergite 5; hair on tergite 1 long and erect, that on tergite 2 moderately long and on following segment short with many long, erect hairs interspersed. Hair of venter long and white, but black on sternite 5, or sternites 4 and 5. Hair of legs whitish, and pale ferruginous on inner side of basitarsi; fringe of hairs on hind basitarsi very long and white. Tegulae and wings as in female.
Head much broader than long, inner orbits moderately divergent above. Vertex moderately impressed between ocelli and margin of eyes. Galae of proboscis virtually bare and shining. Antennae long, moderately slender, reaching base of tergite 3, joint 3 about one-fourth as long as joint 4. Legs normal, middle and hind tarsi long and slender. Sculpture similar to that of female; clypeus moderately shining, with close shallow punctures. Sternite 6 with strong longitudinal impression on each side near base, not terminating in marginal lobe; disk with short, erect black hair from base back to middle of disk, and sparse submarginal hair on apical margin. Parameral lobes of genital armature unusually slender, somewhat bowed and very slightly dilated at apex. Length 9-13 mm, anterior wing 7.5-9.5 mm.