Species account taken from: "A Revision of the Genus Ashmeadiella (Hymen., Megachilidae) Author(s): Charles D. Michener Source: American Midland Naturalist,Vol. 22, No. 1 (Jul., 1939), pp. 1-84"
This is a small and highly variable, finely punctate, species, closely related to altadenae, from which it differs by its smaller size, position of the ocelli (anterior one being well behind midpoint between antennal bases and posterior edge of vertex), and the somewhat more slender median teeth of the sixth tergite of the male. The female of altadenae is unknown, but the female of rufitarsis is similar to sonora, from which it differs by finer punctation and slightly broader cheeks.
Female: Pubescence pale brownish, that of sides of face, cheeks, and sides of thorax wlMtter; inner margins of eyes distinctly converging toward clypeus; transfacial line longer than facial; flagellum light brown beneath; clypeus finely and rather closely punctate, anterior margin reddish brown, narrowly impunc- tate, truncation slightly concave, shorter than distance from its end to eye, ends of truncation prominent and slightly elevated; mandibles red, except black bases and darkened teeth; distance from first to third mandibular tooth much less than width of eye, less than length of last three antennal segments together; cheeks more finely punctate than clypeus, a little more than one- half width of eyes seen from side; anterior ocellus much farther from antennal bases than from posterior edge of vertex; distance between posterior ocelli hardly greater than distance to eye or to posterior edge of vertex; vertex and frons slightly more coarsely punctate than clypeus. Scutum distinctly more sparsely punctate than vertex, without spots of pubescence anteriorly; tegulae testaceous; mesepisterna more finely punctate than scutum; wings slightly dusky; inner margins of inner hind tibial spurs finely serrate with about six- teen small teeth, outer margin with about fourteen very small teeth; outer margin of outer spur with about eight very small teeth, inner margin with fewer similar teeth; tarsi, extreme apices of femora, inner sides of hind tibiae, and to a lesser degree, femora, testaceous. Abdominal tergites distinctly punc- tured, more finely so than scutum, punctures on dorsum of second tergite separated by about one puncture width; sides and posterior margins of first two tergites, and extreme sides of other tergites, red; posterior margins of other tergites testaceous (in paratypes varying from abdomen almost entirely black except for testaceous margins of tergites to abdomen red except for last two tergites which are black); tergites one to five with apical bands of white pubescence; scopa thin, whitish. Lenlgth nearly 4 mm. (fully 4 mm. in some paratypes).
Male: Similar to female; clypeus slightly more finely punctate than vertex; emargination of apical edge of clypeus much shorter than basal width of clypeus and demarked by rather distinct angles; face largely covered with brownish pubescence; distance between posterior ocelli slightly greater than distance to eye or to posterior edge of vertex; tibial spurs similar to those of female; tarsi, extreme apices of femora, and inner sides of apices of hind tibiae rufotestaceous, contrasting more conspicuously with rest of legs than in female. Abdomen black, posterior margins of tergites and teeth of sixth tergite rufotestaceous; lateral teeth of sixth tergite broader than long (longer in some paratypes); median teeth nearly twice as long as broad, rather broad, parallel sided, separated subapically by nearly three times subapical width, emargination between them deeper than a semicircle. Length 31/2 mm. (varying to 4 mm)
The punctation, especially in the male, varies considerably, that of scutum being often distinctly finer as well as sparser than that of vertex.
Holotype female, allotype male, and eleven paratypes: Mount Diablo, Contra Costa County, California, 3800 feet elevation, June 14, 1933, on Eriogonum gracile (P. H. Timberlake). Mr. Timberlake has taken one addi- tional specimen from each of the following localities: one and one-half miles west of Perris, California, June 21, 1938, flying over ground; San Lucas, August 20, 1935, on Eriogonum gracile. Except for two paratypes in my collection, the types have been returned to the Timberlake collection at the Citrus Experiment Station, Universtiy of California, Riversi