Text used courtesy of the Illinois Natural History Survey from:
Thorp, R. W., LaBerge, W. E., 2005. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XV. Subgenus Hesperandrena. Illinois Natural History Survey Bulletin 37: 65-93.
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Andrena compositarum is a relatively small species similar to A. escondida. However, the female of compositarum has the pronotum with complete pronotal angles and dorsoventral ridges, although these may be weak. The female of compositarum can be distinguished by the facial foveae being covered with brown to dark brown hairs and the dorsum of the thorax having at least some brown hairs. The male of compositarum can be separated from that of escondida by having a black clypeus, weak but distinct pronotal angles and dorsolateral ridges, and sterna 2-5 with subapical fimbriae consisting of very long, curved hairs, longer than in escondida males but not as dense nor as white.
FEMALE. MEASUREMENTS AND RATIOS. — N = 6; length, 9-9.5 mm; width, 2.0-2.5 mm; WL, M = 2.69 ± 0.080 mm; FL/FW, M = 0.891 ± 0.008; FOVL/FOVW, M = 2.34 ± 0.061.
INTEGUMENTAL COLOR. — As in escondida in all particulars.
STRUCTURE. — Antennal scape as long as first four flagellar segments or almost so; flagellar segment 1 as long as following three segments or slightly shorter, segments 2 and 3 shorter than broad, of equal length, and slightly shorter than segment 4; segments 5 to 7 or 8 about as long as broad. Eyes, mandibles as in escondida; malar space surpassing tip of galea to slightly shorter; segmental ratio about as 0.5:0.7:0.5:0.5:0.4:0.5. Labial palpus normal, segmental ratio about as 0.9:0.4:0.4:0.5. Labral process short, distinctly but shallowly emarginate; labrum apical to process flat to rounded, dull, often base (near process) with weak, short, longitudinal rugulae, finely tessellate. Clypeus, supraclypeal area and face sculptured as in escondida. Facial fovea extends to distinctly below lower margins of antennal fossae. Genal area (head in profile) more than twice as broad as eye, sculptured as in escondida.
Pronotum with humeral angles and dorsolateral ridges, but relatively weak. Mesoscutum and scutellum with small distinct punctures separated by one to two or three puncture widths, dulled by distinct tessellation. Scutellum as in escondida but basal area not reticulorugose, slightly roughened more than the general tessellation. Mesopleurae dull, tessellate, with scattered small but distinct punctures separated by two to four or more puncture widths.
Metasomal terga sculptured as in escondida; pygidial plate as in escondida but not as distinctly U-shaped, more V-shaped with rounded apex. Sterna sculptured as in escondida.
VESTITURE. — Pale ochraceous to ochraceous except as follows: facial foveae with short brown tomentum, paler on lower third or less; mesoscutum and scutellum with some brown hairs medially, usually largely brown; scopal hairs along posterior margin of tibia and basitarsus usually pale brown to brown. In other respects vestiture as escondida.
MALE: MEASUREMENTS AND RATIOS. — N = 11; length, 8-9 mm; WL, M = 2.60 ± 0.086mm; FL/FW, M = 0.94 ± 0.010; FS1/FS2, M = 2.35 ± 0.081.
STRUCTURE. — Antennae as in escondida but flagellar segment 2 equal to or slightly shorter (allotype) than segment 3. Eyes each about three and a hail' times as long as broad, inner margins diverging strongly towards vertex. Mandibles and galeae as in escondida, Maxillary palpus short, exceeding galea by no more than last maxillary palpal segment, segmental ratio about as 7.0:7.0:4.5:4.0:3.5:3.5. Labial palpus with segmental ratio as 9.0:4.0:3.0:4.0. Labral process deeply emarginate apically, lateral teeth curved down, sharp; labrum apical to process (measured from tips of apical teeth) distinctly shorter than process, shiny. Clypeus, supraclypeal area, lace and vertex above ocelli as in female. Genal area broad, in profile, one and one-half times as wide as width of eye or slightly longer. Pronotum with distinct lateral angles but dorsoventral ridge weak, especially in
lower hall', sculpture of thorax as in female. Metasomal terga sculptured much as in female but shagreening weaker and surfaces shinier, especially on terga 3-6.
Sternal sculpturing as in female. Sternum 7 with apical lobes rounded, emargination narrow, moderately deep. Sternum 8 with apical lobe short, shallowly emarginate medially, neck region almost parallel-sided, slightly broader than apical lobe.
VESTITURE. — Generally white to pale ochraceous, not brown on face or thoracic dorsum as in female. Terga 2-5 with distinct subapical fimbriae consisting of long, relatively sparse hairs (especially laterally) which curve downward, unlike the dense white bands of straight shorter hairs of escondida.
TYPE MATERIAL. — The holotype female (UCD), allotype male (UCD), one female and one male paratype (INHS) of compositarum were collected from Layia chrysanthemoides at Dixon (9 miles S), Solano Co., California, by R.W. Thorp on April 17, 1969. The holotype and allotype are deposited in the California Academy of Natural Sciences. Paratypes are in the collections of the University of California at Davis and the Illinois Natural History Survey in Champaign. Four female and nine male paratypes were collected from California (Fig. 3) as follows:
SOLANO CO.: Dixon (9 mi. S). 1 female. May 8, 1969 from Layia chrysanthemoides, R.W. Thorp; 1 female. May 1,1969, from L chrysanthemoides, B.J. Donovan; 1 female, 1 male, April 24, 1969 from L. chrysanthemoides, R.W. Thorp; 2 males from L. chrysanthemoides, April 24, 1969, B.J. Donovan. STANISLAUS CO.: LaGrange (1 mi. N). 1 female, 4 males, S.M. Fullerton; LaGrange (3 mi. N). 2 males, Mar. 26, 1960, S.M. Fullerton.