Reprinted with permission of the University of Nebraska State Museum from:|
LaBerge, W. E. 1967. A revision of the bees of the genus Andrena of the Western Hemisphere. Part I. Callandrena (Hymenoptera: Andrenidae). Bulletin of the University of Nebraska State Museum 7: 1-316.
Described in that work under the synonymous name: Andrena humeralis LaBerge
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Andrena humeralis is closely related to A. accepta from which it can be distinguished readily by the well-developed humeral angles on the pronotum. This is an unusual character in the subgenus Callandrena and will distinguish this species from all others. In addition humeralis differs from accepta in both sexes by a shorter vertex and less punctate terga, in the females by a more strongly bidentate process and lack of yellow on the clypeus, and in the males by a shorter clypeus and broader genal areas.
FEMALE. MEASUREMENTS AND RATIOS. — N = 1; length, about 11 mm; width, about 3.5 mm; wing length, 1.08 mm; FL/FW = 1.08; FOVL/FOVW = 2.12.
INTEGUMENTAL COLOR. — Color as in accepta except as follows; clypeus without yellow; wing membranes infumate apically; veins reddish-brown; pygidial plate yellow medially, rufescent peripherally.
STRUCTURE. — Flagellar segments 1-3 distinctly shorter than scape, segments 2 and 3 equal to one another, shorter than succeeding segments and together equal to about two-thirds length of first segment. Eye about four times as long as broad, inner margins slightly converging above. Malar space as in accepta. Mandible as in accepta but ventrobasal lamella poorly developed. Galea as in accepta. Maxillary palpus shorter than galea, in ratio of about 3.0:2.3:1.0:1.0:1.5. Labial palpus with first segment compressed and strongly curved, in ratio of about 4.0:1.2:1.0:1.2. Labral process about three times as long as broad, strongly bidentate. Clypeus flat with round, coarse punctures separated mostly by one-half to one puncture width, surface shiny, only slightly dulled by fine shagreening. Supraclypeal area with minute crowded punctures, surface shiny. Genal area as in accepta. Vertex above lateral ocellus equals about one and one-half an ocellar diameter, sculptured as in accepta. Face as in accepta. Facial fovea longer than in accepta, length equals about half length of eye.
Pronotum with well-developed humeral angles with a blunt ridge running ventrad from angle but interrupted by the pronotal suture, sculptured as in accepta. Mesoscutal and scutellar sculpturing as in accepta but mesoscutum shinier. Propodeum as in accepta but enclosure with transverse rugulae in basal two-thirds. Mesepisternal punctures separated mostly by one puncture width, otherwise as in accepta. Metepisternum impunctate below, surface shiny. Middle basitarsus about as broad as hind, not markedly expanded medially. Hind tibia, tibial spurs, and wings as in accepta.
Metasomal tergum 1 with punctures small, round, separated mostly by one to two puncture widths, smaller and more crowded near apex, surface shiny, unshagreened. Terga 2-4 similar but slightly dulled by shagreening at least on tergum 4. Tergum 5 with punctures and shagreening denser, dulling surface. Pygidial plate narrow, an elongated V in shape, with rounded apex. Sterna as in accepta.
VESTITURE. — Uniformly ochraceous except inner surfaces basitarsi brown; distribution and types of hairs as in accepta.
MALE. MEASUREMENTS AND RATIOS. — N = 1; length, about 11 mm; width, about 2.5 mm; wing length, 3.3 mm; FL/FW = 0.81; FS1/FS2 = 2.00.
INTEGUMENTAL COLOR. — Color as in female but clypeus entirely yellow except narrow brown apical border and small brown maculae at tentorial pits; distitarsi, basitarsi and tibiae rufescent (but tibiae darker especially basally).
STRUCTURE. — Antennae short, barely reaching tegulae, scape longer than segments 1-3; flagellar segment 1 longer than segments 2 plus 3 which are subequal in length and each shorter than succeeding segments. Eye slightly longer than three times breadth, inner margins subparallel. Malar space, mandibles, galeae, maxillary and labial palpi, and labral process as in female but mandible lacks ventrobasal lamella. Clypeus flat, barely, if at all, protruding beyond lower level of eyes, with coarse round punctures but sparse along midline, surface shiny. Supraclypeal area, frons and vertex as in female but vertex less punctate and shinier laterad of ocelli. Genal area almost twice as broad as eye in profile, with small punctures separated by one to two puncture widths, surface shiny, unshagreened.
Structure of thorax as in female except as follows: pronotum with humeral angle more distinct and ridge extending down from angle better developed, surface posterior to ridge with several vertical rugulae; propodeum with enclosure with more distinct transverse rugulae, outside of enclosure with small punctures separated by two or more puncture widths, surface dulled by coarse reticular shagreening. Tergal and sternal sculpturing as in female but punctures of terga even more widely spaced (mostly by one to three puncture widths) and surfaces everywhere shinier. Sternum 6 extremely shallowly and broadly emarginate, flat.
Genital capsule and sterna 7 and 8 similar to those of accepta but note the following: dorsal lobes of gonocoxites narrow and more pointed; gonoforceps slightly blunter, penis valves narrower near base; sternum 7 with apical emargination forming a right angle; sternum 8 shallowly emarginate.
VESTITURE. — Generally hair color cinereous; distribution and type as in accepta.
TYPE MATERIAL. — The holotype female (CAS) was collected by B. J. Adelson in San Antonio, Texas (Loop 13), October 25, 1952, on Baccharis sp. The allotype male was collected by A. H. Alex in Bexar County, Texas, November 7, 1954, on Aster sp. The allotype male belongs to the Texas A. and M. College, College Station, Texas, but is on indefinite loan to the Illinois Natural History Survey.