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 dissona is a small bee which has a distinct pronotal humeral angle and lateral ridge in both sexes. The female can be distinguished from that of other species with distinct pronotal angle and ridge by having a black, moderately shiny to shiny mesoscutum and scutellum, the apical fascia of tergum 2 usually broadly interrupted medially and has the mesoscutal punctures (especially just inside of parapsidal lines) more distinct and more crowded. The male has a partly yellow clypeus and sterna 2-5 with subapical fimbriae of long, down-curved, weakly plumose, relatively sparse hairs.
FEMALE. MEASUREMENTS AND RATIOS. — N = 5; length, 7.0-7.5 mm; width, 2.252.50 mm; wing length, 2.44 ± 0.287 mm; FL/FW, M = . 0.85 ± 0.011; FOVL/FOVW, M = 2.6310.16.
INTEGUMENTAL COLOR. — Black except as follows: metallic tints occasionally present on Ace above antennal fossae but absent on mesonotum and mesepisternum; metasomal terga with apical areas entirely or largely hyaline, clear to yellowish; terga 1 and 2 with basal areas with small, apical, brownish yellow, apicolateral spots, with a narrow yellowish line connecting spots across tergum; sterna with apical areas hyaline; wing membranes hyaline, veins reddish brown.
STRUCTURE. — Antenna! scape equal to or slightly less than first four flagellar segments; flagellar segments as in baeriae but segments 5-9 about as long as broad or slightly longer, segment 10 distinctly longer than broad. Mandibles, malar space and galeae as in baeriae but galeae shinier, shagreening delicate (not as shiny as in perdissona). Labrum short and broad as in baeriae but usually not emarginate apicomedially. Maxillary palpus as in escondida but segmental ratio about as 1.0:1.0:0.8:0.6:0.4:0.7. Labial palpus as in escondida but ratio about as 1.0:0.6:0.4:0.7. Clypeus, supraclypeal area and face above antennal fossae as in escondida but clypeal punctures somewhat more abundant in apical half and more distinct. Facial fovea and genal area as in baeriae. Vertex above lateral ocellus equals about half an ocellar diameter.
Pronotum with distinct humeral angles and lateral ridges. Mesoscutum moderately shiny, shagreening coarse; punctures moderately well formed, in area just mesad of parapsidal line mostly separated by one puncture width or slightly less. Scutellum similar but occasionally shagreening less distinct, moderately shiny. Propodeum and pleurae as in escondida.
Metasomal terga sculptured as in escondida. Pygidial plate as in escondida, with broad raised rim especially in apical two-thirds. Sterna 2-5 as in escondida.
MALE: MEASUREMENTS AND RATIOS. — N = 15: length. 6.5-7.0 mm; width, 2.0-2.5 mm; wing length, M = 2.23 ± 0.128 mm; FL/FW, M = 0.86 ± 0.007; FS1/FS2, M = 2.13 ± 0.065.
INTEGUMENTAL COLOR. — Black except as follows: clypeus with cream-colored or pale yellow mediobasal macula, apical third or fourth and lateral angles of clypeus black; face above antennal fossae and mesepisterna often with faint metallic reflections; flagellum below dark reddish brown; wing membranes hyaline, clear, veins reddish brown; metasomal terga and sterna with apical areas hyaline, colorless to slightly yellowed basally.
STRUCTURE. — Antennae short, female-like; flagellar segment 1 longer than segments 2 plus 3, segment 2 subequal in length to 3 which is slightly shorter than 4, segments 5-10 about as long as broad, 11 distinctly longer than broad. Eyes each about one and one-half times as long as broad, inner margins diverge towards vertex. Mandibles and galeae as in baeriae. Maxillary palpus as in female but segmental ratio about as 1.0:1.0:0.7:0.6:0.4:0.7. Labia! palpi; J baeriae but ratio about as 1.0:0.3 :C 1- ) ! Labral process and labrum as in escondida but not at all or only slightly emarginate apicomedially. Clypeus as in baeriae but punctures hardly visible. Supraclypeal area and face above antennae as in baeriae. Vertex above lateral ocellus equals about half an ocellar diameter.
Pronotum with distinct humeral angles and lateral ridges much as in baeriae. Thoracic sculpturing as in female but scutellum occasionally moderately shiny, shagreened.
Metasomal sculpturing as in female but terga 3-5 moderately shiny. Sterna as in female. Sternum 7 (Fig. 32) with apical lobes narrow, sides not strongly angulate, emargination deep and narrow; sternum 8 (Fig. 33) much as in lativentris but much smaller.
VESTITURE. — White to pale ochraceous but on inner surfaces of tarsi yellow and on dorsum of thorax often slightly darker ochraceous. Metasomal terga 2-5 with weak apical pale fasciae, those on terga 2 and 3 interrupted medially, usually by more than a third of width of tergum. Sterna 2-5 with subapical fimbriae of relatively sparse, long, curved downward, plumose hairs.
TYPE MATERIAL. — The holotype female of dissona (CAS) was collected at Strathmore, Tulare Co., California, from flowers of Baeria chrysostoma. March 29, 1937 by P.H. Timberlake. The allotype male of dissona (CAS) was collected at Earlimart, Tulare County from flowers of Baeria tenella, March 9, 1937 by P.H. Timberlake. Four female and fifteen male paratypes from California (Fig. 3) (UCB, UCD, INHS, CAS, LACM) are as follows:
CALIFORNIA. SOLANO CO.: Dixon (9 mi. S). — 1 male, April 24,1969 from Layia chrysanthemoides or Baeria chrysostoma, B.J. Donovan; 1 male, April 24, 1969 from L. chrysanthemoides or B. chrysostoma, R.W. Thorp; 1 male April 17, 1969 from L. chrysanthemoides, R.W. Thorp; 1 male April 17, 1969, from L. chrysanthemoides D.L. Briggs. Dixon (11 miles S at Dozier). — 1 male April 17,1969, from Layia chrysanthemoides, D.L. Briggs. YOLO CO.: Davis — 1 male. May 12, 1937, M. DuBois.