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Andrena macrocephala Cockerell, 1916
Life   Insecta   Hymenoptera   Apoidea   Andrenidae   Andrena

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Reprinted with permission of the American Entomological Society from: LaBerge, W. E. 1985. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XI. Minor subgenera and subgeneric key. Transactions of the American Entomological Society 111: 440-567.

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This species can be recognized readily in either sex by the narrow dart-like galeae, much like those of the Belandrena but dulled by fine shagreening. In addition the female of macrocephala has the trochanteral flocculus composed of short hairs throughout, and the male has a long first flagellar segment.

FEMALE. MEASUREMENTS AND RATIOS. N = 20; length, 10-12 mm; width, 3-4 mm; wing length, M = 3.57 0.116 mm; FL/FW, M = 0.90 0.006; FOVL/FOVW, M = 3.11 0.044.

INTEGUMENTAL COLOR. Black except as follows: mandible with at least apical third and extreme base rufescent, often entirely so; flagellar segments 2-10 dark reddish brown below. Wing membranes hyaline; veins dark brown; tibial spurs brown. Metasomal terga with apical areas rufescent; sterna often dark rufescent basally.

STRUCTURE. Antennal scape as long as first three flagellar segments or slightly I longer; flagellar segment 1 about as long as segment 2 plus 3 plus half of 4; median segments longer than broad. Eyes each about four times as long as broad, inner margins converging slightly toward vertex. Malar space long, minimum length equals one-fourth basal mandibular width or slightly more. Mandibles bidentate, overlapping by less than one-fifth mandible length when closed. Galea dart-like, narrow, outer margin straight; surface opaque, finely tessellate. Maxillary palpus relatively short, surpassing galeae by about one palpal length; segmental ratio about 1.0:0.9:0.7:0.7:0.5:0.5. Labial palpus relatively short (especially first segment); segmental ratio about 1.0:0.7:0.5:0.5. Labral process entire, short, rounded or weakly emarginate; labrum below process with a strong transverse shiny sulcus without cristae. Clypeus evenly rounded from side to side, with small inconspicuous punctures separated by one to two or three puncture widths, with impunctate midline; surface dulled by dense reticular shagreening. Supraclypeal area with close-set punctures and fine shagreening dulling surface. Face above antennal fossae with fine rugulae diverging toward ocelli and fine punctures. Facial fovea shallow, large, separated from lateral ocellus by one ocellar diameter or more, extending below to a line below posterior clypeal margin. Vertex above lateral ocellus equals about one ocellar diameter; surface opaque, finely tessellate. Genal area broader than eye in profile (about 3:2), coarsely reticularly shagreened with scattered minute obscure punctures.

Pronotum without humeral angles; dorsoventral ridges weak, rounded, or not at all evident; surface opaque, reticularly shagreened. Mesoscutum, scutellum, and metanotum opaque, coarsely tessellate, punctures present but minute and obscure. Propodeum with dorsal enclosure smoothly tessellate; outside of enclosure tessellate with sparse minute round punctures not at all roughening surface. Mesepisternum opaque, finely tessellate, punctures obscure. Pterostigma as narrow as or narrower than prestigma to wing margin; vein 1st m-cu usually meets second submarginal cell near its middle.

Metasomal terga 1-5 with basal areas dulled by reticular shagreening, punctures minute, obscure, progressively more abundant posteriorly; apical areas with reticular shagreening finer, but reticles larger, surfaces moderately shiny. Pygidial plate V-shaped with rounded apex; without raised internal triangular area. Sterna 2-5 densely punctate in apical halves (except extremely narrow, impunctate, apical areas), sparsely punctate basally, surfaces moderately shiny, reticular shagreening weak.

VESTITURE. Dark brown except as follows: dorsum of thorax pale ochraceous to dark red; vertex with mixed pale and dark. Propodeal corbiculum undeveloped, dorsal hairs short, anterior and internal hairs absent; trochanteral flocculus with hairs all short; scopal hairs long, dense, largely simple.

MALE. MEASUREMENTS AND RATIOS. N = 20; length, 8-10 mm; width, 1.5-2.5 mm; wing length, M = 3.25 0.186 mm; FL/FW, M = 0.86 0.008; FS1/FS2, M = 3.04 0.029.

INTEGUMENTAL COLOR. As in female except as follows: mandible never entirely rufescent; clypeus yellow except narrow anterior margin, small triangular tentorial maculae, and extreme lateral angles; most often narrowly darkened along posterior margin and between tentorial maculae and posterior margin.

STRUCTURE. Antennal scape almost as long as first three flagellar segments; flagellar segment 1 as long as succeeding two segments or longer; flagellar segment 2 quadrate, succeeding segments longer than broad. Eyes each three and one-third times as long as broad, inner margins converging slightly toward vertex. Malar space, galea, maxillary palpus, and labial palpus as in female. Mandible simple, long, abruptly turned inward at two-fifths length from base (but not at a right angle). Labral process entire or weakly emarginate apically, shiny. Clypeus flat, with small sparse punctures separated mostly by two to three puncture widths or more, surface moderately shiny, weakly reticularly shagreened. Supraclypeal area as in female. Face above antennal fossae with strong longitudinal rugae, below ocelli rugae diverge toward ocelli. Vertex as in female, but above lateral ocellus equals one and one-half to two ocellar diameters. Genal area in profile almost twice as broad as eye, rounded posteriorly.

Pronotum with distinct but rounded dorsoventral ridge broadly interrupted by oblique suture; humeral angle lacking, dorsal margin short; sculptured as in female. Thoracic sculpturing and wing venation as in female.

Metasomal terga 1-6 sculptured as in female terga 1-5, but reticular shagreening slightly weaker, surface shinier but generally dull. Tergum 7 with extremely narrow, pointed, pygidial area present but usually hidden by long hairs. Sterna 2-5 moderately shiny, sparsely punctate, and reticularly shagreened. Sternum 6 weakly curved down, not reflexed at margin. Sternum 7 acutely pointed. Terminalia as in figures 114-118. Note penis valves and apicolateral lobes of gonocoxites elongated and attenuated; penis valves relatively narrow basally; sternum 8 elongate and pointed (similar to that of A. cressonii).

VESTITURE. Generally pale ochraceous to reddish ochraceous except as follows: face along inner margins of eyes and below vertex almost to antennal fossae dark brown or brown and pale mixed; terga 2-6 dark brown or largely so; tibiae and tarsi often with outer surfaces brown. Sternum 6 with lateral tufts of highly plumose, long hairs directed laterad from bare midline.

Scientific source:

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Hosts · map
FamilyScientific name @ source (records)
Boraginaceae  Nemophila menziesii @ AMNH_BEE (4)
Hydrophyllaceae  Nemophila menziesii @ BBSL (1)

Nemophila sp @ BBSL (1)
_  Withheld @ BBSL__YOSE (40); BBSL (82); BBSL__PINN (16)

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Updated: 2021-05-13 13:36:53 gmt
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