Extracted from: TImberlake P. H., (1958). 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 III. University of California Press Berkeley and Los Angeles 1958, Volume 14, No. 5, pp. 303-410, plates 4-15.|
The characters separating rivalis from swezeyi and both species from zonalis are given in the preceding synoptic key. Although both rivalis and swezeyi fly from late June into August and zonalis in late August and September, the flight range must overlap to a certain extent. Perhaps both species hybridize with zonalis, which would help to explain the puzzling intermediate specimens, especially certain almost indeterminate specimens found flying with zonalis bernardina in the San Bernardino Mountains.
Female.—Head and thorax dark green, the propodeum more bluish. Base of mandibles, clypeus, lateral marks, and usually a supraclypeal mark, often divided into two spots, yellow. Mandibles shading into testaceous at middle and red at apex. Labrum usually more testaceous than yellow. Clypeus with two brown or blackish stripes on upper half of disk, which are sometimes confluent to form a large blotch that engulfs the clypeal dots. Subantennal plates and supraclypeal area except for the more or less evanescent yellow mark or spots black. Rarely (as in female from Sequoia National Park) the face entirely dark, except lateral marks and an evanescent yellow streak in middle of clypeus. Apex of tubercles, a mark on each side of hind border of pronotal disk, and sometimes the collar yellow. Abdomen blackish, with a pale yellow band on tergites 1 to 5; light band on tergite 1 represented by four small spots or dots, or reduced to a spot on lateral margins; bands on following segments arcuate and curved back¬ward at outer ends, interrupted medially at least narrowly and sometimes broadly, with the band on tergite 2 represented by an oblique mark far toward sides; band on tergite 5 sometimesabsent or concealed by preceding segment. Legs fuscous or blackish, the tip of front and middle femora, and anterior side of their tibiae yellow. Antennae fuscous, the flagellum brownish yellow beneath, and scape clear yellow except narrowly above. Tegulae pale testaceous, with the extreme base brown. Wings dusky hyaline, the nervures brownish testaceous, the subcosta fuscous.
Structual characters about as in zonalis, but head more distinctly broader than long, the frons more strongly punctured, and the pygidial plate narrower, less arcuate on margins and more weakly notched at apex. Marginal cell also shorter, hardly more than twice as long as wide, with part beyond stigma scarcely longer than the part beneath. Length, 4.5-6 mm.; anterior wing, 3.5-3.9 mm
Male.—Dark blue-green. Mandibles except red tips, labrum, and face below level of antennae yellow, except subantennal plates entirely black or with a yellow mark usually not covering more than half the surface. Abdomen more or less fuscous or blackish above, with a yellow band on tergites 2 to 6; light bands interrupted medially, that on tergite 2 sometimes interrupted also 8ublaterally, or reduced to four small spots, but those on tergites 5 and 6 usually very broad and often entire; tergite 7 generally yellowish, with a brown mark on each side of disk. Venter of abdomen dull yellow, more or less suffused with brown at junction of segments. Pronotum, antennae, tegulae, and wings about as in female; legs similar, but front and middle femora generally broadly yellow in front, the hind femora yellow in front and beneath, and the hind tibiae narrowly yellow beneath.
Structurally much the same as the male of zonalis. Head slightly more transverse, with punctures of frons more distinct. Marginal cell shorter and broader. Aedeagus similar, but caulis with a narrower oval form as seen from above, with margin of dorsal part of parameral lobes somewhat overriding the inferior margin; fused body of sagittae from base to the subapical angulations about three times longer than broad. Length, 4.25-5.5 mm.; anterior wing, 3.1-3.5 mm.
Nine males, 16 females (holotype male, allotype, and paratypes), Big Pines Camp, about 6,000 feet, San Gabriel Mts., Los Angeles County, California, on Erigeron foliosus var. stenophyllus, July 13-16, 1927 (Timberlake). Additional paratypes as follows: 9 males, 30 females, Big Pine Camp, on same flower, Aug. 2, 1944; 5 males, 7 females, Big Bear Lake, Bear Valley, San Bernardino Mts., on 'Aster canescens, and 5 males, 1 female on Erigeron divergent, Aug. 11, 1933 (Timberlake); 1 male, Three Rivers, Tulare County, (Culbertson); 4 males, 1 female, Tokapah Valley, Sequoia National Park, on Aster adscendens, Aug. 23,1933 (C. D. Michener); 2 males, 4 females, Mineralking, Tulare County, July 25 to Aug. 1, 1935 (Q. E. Bohart) ; 4 males, 4 females, General Grant Park, 5,500 feet, Aug. 25, 1946 (H. A. Scullen); 1 female, Frazier Park, Kern County, July 14,1946; and 7 females, Lake Arrowhead, San Bernardino Mts., on Aster, July 9,1956 (P. D. Hurd, Jr.).
Types in the U. S. National Museum (No. 43,419); paratypes in the collections of the University of California at Berkeley, Davis, and Riverside, Oregon State College, and the University of Kansas.