Reprinted with permission of the American Entomological Society from:
LaBerge, W. E., Ribble, D. W. 1975. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VII. Subgenus Euandrena. Transactions of the American Entomological Society 101: 371-446.
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This small California species is another annectant species between the more extreme type of Euandrena such as caerulea and the Thysandrena. It resembles closely caerulea except for the simple scopal hairs of the female and the presence of weak but distinct pale apical fascia on the first tergum. The female of dissimulans has an exaggeratedly broad head and the male has an unusually short first flagellar segment relative to the second segment.
FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-10 mm; width, 2.5-3.5 mm; wing length, M = 3.37 ± 0.257 mm; FL/FW, M " 0.89 ± 0.005; FOVL/FOVW, M = 3.44 ± 0.048.
INTEGUMENTAL COLOR. — Black except as follows: with green to bluish-green metallic reflections; tergal apical areas often with violaceous reflections; clypeus with faint to bright violaceous reflections; mandible largely rufescent; flagellum reddish-brown below; wing membranes slightly infumate, veins reddish-brown to dark brown; tegula testaceous to reddish-brown; terga 1-5 with narrow apical hyaline apices colorless; legs slightly rufescent, tibial spurs testaceous.
STRUCTURE. — Antennal scape equal in length to first four and one-half flagellar segments; flagellar segment 1 equal in length to segments 2 plus 3; segments 2-8 at least slightly broader than long. Eyes each about four and one-third times as long as broad, inner margins converging slightly towards mandibles. Mandible and galea as in caerulea but galea moderately shiny, shagreening extremely fine. Maxillary palpus as in caerulea but segmental ratio about as 0.9:1.0:0.8:0.8:0.6:0.8. Labial palpus as in caerulea but ratio about as 1.0:0.7:0.4:0.7. Labral process entire, trapezoidal, about one and one-half times as long as broad, rarely extremely gently emarginate apicomedially; labrum below process shiny, without cristae. Clypeus as in caerulea but obscure punctures slightly more evident and crowded, mostly confluent. supraclypeal area dulled by minute crowded punctures and coarse shagreening. Face above antennal fossae with longitudinal rugulae (slightly coarser than in caerulea) and interrugal punctures. Facial fovea as in caerulea. Vertex short, above lateral ocellus equals half an ocellar diameter or slightly more, facial rugulae extend to area beside lateral ocellus. Genal area as in caerulea but slightly broader.
Thoracic structure and sculpturing as in caerulea except as follows: hind wing with vannal lobe moderately broad, equal in width at base of excision to about one and one-half times end of cell Cu; hind tibia normal, not cuneate.
Metasomal tergum 1 with punctures separated mostly by two puncture widths but slightly more crowded along base of apical area; terga 2-4 with basal area punctures usually distinct, separated largely by one puncture width; surfaces terga often dulled by coarse reticular shagreening, but frequently almost without shagreening except at extreme bases. Pygidial plate as in caerulea. Sterna as in caerulea but often shiny.
VESTITURE. — Generally white to pale ochraceous except as follows: facial fovea with short hairs often brown; vertex often with long dark brown to brown hairs; basitibial plate and surrounding area with hairs brown. Thoracic dorsum with hairs denser than in caerulea. Terga 2-4 with complete apical white bands (occasionally extremely narrowly interrupted medially on tergum 2); tergum 1 with weak apical white band often interrupted medially. Scopal hairs simple, long. propodeal corbicula incomplete anteriorly with several long simple internal hairs. Femoral dorsal hairs plumose but not so densely as in caerulea. Trochanteral flocculus weak.
MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7-9 mm; width, 1.5-2.0 mm; wing length, M = 2.84 ± 0.136 mm; FL/FW, M = 0.92 ± 0.005; FS1/FS2, M = 1.03 ± 0.016.
INTEGUMENTAL COLOR. — Generally as in female but metallic reflections tend to be greenish-blue or blue rather than green.
STRUCTURE. — Antenna long, reaching posterior margin of metanotum in repose; scape length equal to first two and one-third flagellar segments; flagellar segment 1 about equal in length to segment 2, segments all one and one-half to two times as long as broad. Eyes each slightly less than four times as long as broad, inner margins strongly converging towards mandibles. Mandible and galea as in female. Maxillary palpus as in female but segmental ratio about as 1.0:0.8:0.7:0.7:0.5:0.7. Labial palpus as in female but ratio about as 1.0:0.5:0.3:0.4. Labrum as in female but process often emarginate apicomedially. Clypeus, supraclypeal area, face, vertex and genal area as in female.
Thoracic structure and sculpturing as in female but propodeum outside of enclosure with punctures slightly more distinct.
Metasomal terga sculptured as in female but punctures slightly sparser (separated mostly by one and one-half puncture widths). Sterna 2-5 weakly punctate, usually shiny. Sternum 6 flat, emarginate.
Terminalia as in Figures 55-59; note the following: as in subdepressa but dorsal lobe gonocoxite shorter; gonostylus less hairy.
VESTITURE. — Generally white with long brown hairs on vertex, on face along inner margins of compound eyes, and below ocelli. Sterna 1-5 with pale apical fasciae but that on tergum 1 weak and often interrupted medially. Sterna without subapical fimbriae.