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.
Please report text errors to: leah at discoverlife dot org.
This small dark species is closely related to Andrena nigrihirta and resembles the darker specimens of the latter. A. hamulata can be distinguished from nigrihirta in both sexes by the more coarsely punctate, shinier terga, mesoscutum and antennal scapes and by the robust, hooked, tibial spurs of the middle and hind legs. The face of hamulata is somewhat longer than that of nigrihirta and approaches that of lawrencei.
FEMALE. MEASUREMENTS AND RATIOS. — N = 12; length, 9-12 mm; width, 2.5-3.5 mm; wing length, M = 3.69 ± 0.244 mm; FL/FW, M = 1.14 ± 0.010; FOVL/FOVW, M = 4.24 ± 0.091.
INTEGUMENTAL COLOR. — Black except as follows: mandible with apical half rufescent; flagellum dark brown to reddish-brown below; tegula dark rufescent; wing membranes infumate, brownish, veins dark reddish-brown; tergal apical areas often moderately rufescent; sterna often rufescent; tarsi usually dark brown (occasionally legs slightly rufescent but hind tibiae never orange); tibial spurs testaceous to yellow.
STRUCTURE. — Antennal scape about as long as first four flagellar segments; flagellar segment 1 about as long as segments 2 plus 3 or slightly longer, segment 2 shorter than 3 and broader than long, segment 3 quadrate, remaining segments slightly longer than broad. Eyes each about three and one-half times as long as broad, inner margins parallel or converging slightly towards mandibles. Mandible as in lawrencei. Galea as in lawrencei but shorter. Maxillary palpus moderately long, segmental ratio about as 0.9:1.0:0.9:0.9:0.9:0.8. Labial palpus as in lawrencei but shorter, ratio about as 1.0:0.6:0.5:0.6. Labral process large. entire or slightly indented apically (as in holotype). shiny, trapezoidal or rounded; labrum below process often with several short cristae near process. Clypeus as in nigrihirta but punctures more regularly coarse. Supraclypeal area with minute crowded punctures, often moderately shiny, interpunctural shagreening fine. Face above antennal fossae as in nigrihirta. Vertex as in nigrihirta but slightly longer, above lateral ocellus equal to about three-fourths an ocellar diameter; with distinct punctures and dulled by dense shagreening. Genal area and facial fovea as in lawrencei.
Thoracic sculpturing as in nigrihirta except mesoscutal and scutellar punctures deeper, coarse, separated mostly by half a puncture width or less, surfaces finely shagreened, moderately shiny. Wings as in lawrencei. Middle tibial spur and anterior hind tibial spur distinctly hooked at apices, tibial spurs shorter and more robust than in nigrihirta or lawrencei. Tarsal claws normal.
Metasomal terga 2-4 with discs closely and deeply punctate, punctures mostly separated by half a puncture width or less; apical areas similarly punctate but punctures sparser in median thirds; tergum 1 similar to 2 but discal punctures separated by two or more puncture widths. Pygidial plate and sterna as in nigrihirta.
VESTITURE. — Generally dark brownish-black except dorsum of thorax ochraceous at least on scutellum (as in holotype) or ochraceous but with a broad transverse brown patch on mesoscutum, or entirely pale; tergum 1 often with sparse long pale hairs near apex of disc (not in holotype); tibial scopal hairs mostly white (except along posterior margin below basitibial plate). Pollen-collecting hairs as in lawrencei and nigrihirta.
MALE. MEASUREMENTS AND RATIOS. — N = 14; length, 8-10 mm; width, 2-3 mm; wing length, M = 3.31 ± 0.261 mm; FL/FW, M = 1.17 ± : 0.008; FS1/FS2, M = 1.62 ± 0.049.
INTEGUMENTAL COLOR. — Black with exceptions as in female but mandible with apical third or less rufescent and wing membranes less infumate, yellowish-brown.
STRUCTURE. — Antennae, eyes, mandibles and galeae as in nigrihirta but scapes with distinct crowded punctures, moderately shiny. Maxillary palpus as in female but segmental ratio about as 0.8:1.0:0.8:0.8:0.8:0.9. Labial palpus as in female but ratio about as 1.0:0.6:0.5:0.5. Labrum as in female but usually slightly indented apicomedially. Clypeus as in female but punctures slightly smaller and more regularly spaced. Supraclypeal area, face above antennal fossae, vertex and genal areas as in female.
Thoracic sculpturing as in female with mesoscutum and scutellum shiny to moderately shiny and coarsely punctate. Wing venation as in nigrihirta. Tibial spurs stout and hooked as in female. Tarsal claws normal.
Metasomal tergal sculpturing as in female but tergum 5 similar to 4 and terga 1-5 with apical area punctures sparser in median halves. Sterna as in nigrihirta.
Terminalia as in figures 20-24; note the following: penis valves inflated dorsally and abruptly smaller near base; gonocoxite blunt; sternum 7 shallowly emarginate; sternum 8 distinctly broadened at apex.
VESTITURE. — White or ochraceous except as follows: vertex, face near compound eyes and lateral corners of clypeus dark brown (allotype) to head entirely dark except a few pale hairs surrounding antennal fossae; tegulae with dark hairs; mesepisternum may have dark hairs mixed with pale in upper third (not in allotype); mesoscutum and scutellum often with dark hairs mixed with pale medially (not in allotype) and dorsal thoracic hairs often with reddish tint (not allotype); terga with short erect dark brown hairs except tergum 1 pale at least in apical area and terga 2-4 with broadly interrupted, apical, pale fasciae (rarely complete on tergum 4); sterna 2-5 with weak subapical fimbriae incomplete laterally and composed of a single file of short pale hairs.