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Andrena isocomae Timberlake, 1951
Andrena (Pterandrena) isocomae Timberlake, 1951

Life   Insecta   Hymenoptera   Apoidea   Andrenidae   Andrena
Subgenus: Callandrena_sensu_lato

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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.

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This small species from California is closely related to A. gardineri. The female of isocomae can be distinguished from that of gardineri by its slightly smaller size, longer and broader facial foveae, and slightly paler vestiture. The male of isocomae is readily distinguished from that of gardineri by its large parocular yellow maculae and longer third flagellar segment (distinctly longer than the second segment which is unusually short).

FEMALE. MEASUREMENTS AND RATIOS. N =20; length, 9-11 mm; width, 2.5-3.5 mm; wing length, M= 3.30 0.184 mm; FL/FW, M= 1.00 0.006; FOVL/FOVW, M = 2.48 0.020.

INTEGUMENTAL COLOR. Black except is follows: mandible usually with apical half dark rufescent; flagellum entirely (or segments 2-10) dark reddish-brown below; tegulae translucent brownish-red; wing membranes hyaline, colorless, veins reddish-brown; terga 1-5 with epical areas hyaline, colorless, often narrowly rufescent just basad pf colorless margins; sterna 2-5 narrowly hyaline apically, dark rufescent basally; distitarsi dark rufescent; tibial spurs yellow.

STRUCTURE. Antennae short; scape length slightly less than flagellar segments 1-4; flagellar segment 1 equals succeeding two and one-third segments in length; segment 2 extremely slightly shorter than 3 and 3 shorter than segment 4; segments 4-8 subquadrate to quadrate, 9 and 10 longer than broad. Eye about three and one-fourth times as long as broad, inner margins converging towards mandibles. Malar space, mandible and galea as in gardineri. Maxillary palpus as in gardineri but segmental ratio about 1.2:1.0:0.6:0.6:0.5:0.6. Labial palpus as in gardineri but segmental ratio about 1.9:1.0:0.7:1.0. Labral process strongly bidentate. Clypeus as in gardineri but punctures absent along narrow midline especially in basal half and shiny, reticular shagreening restricted to posterior periphery. Supraclypeal area with minute punctures, shiny, shagreening absent or extremely delicate. Genal area as in gardineri but posteriorly punctures separated by two puncture widths and surface shiny, unshagreened or delicately so. Vertex above lateral ocellus equals slightly more than one ocellar diameter, punctate as in gardineri, surface shiny, with delicate reticular shagreening. Face above antennal fossae as in gardineri. Facial fovea long and broad, extending below to level of lower margins of antennal fossae, separated from lateral ocellus by about half an ocellar diameter.

Pronotum as in gardineri but shinier, shagreening delicate. Mesoscutum and scutellum as in gardineri with punctures separated mostly by half a puncture width and surface shiny, unshagreened or extremely delicately so. Tegulae, parapsidal line and metanotum as in gardineri. Propodeum with dorsal enclosure roughened in basal half, elsewhere tessellate; dorsolateral surfaces with punctures small and shallow, moderately shiny, reticularly shagreened; posterior surface with small round punctures separated mostly by two to three puncture widths, shiny, reticular shagreening delicate; corbicular area with scattered punctures in anterior half, shiny, unshagreened or delicately so. Mesepisternum wit small punctures separated by one to two puncture widths anteriorly, less posteriorly, surface shiny, delicately and reticularly shagreened Metepisternum with lower portion impunctate, delicately shagreened, shiny, upper third with small punctures and reticular shagreening moderately dulling surface. Middle basitarsus somewhat expanded, slightly broader than hind basitarsus medially. Forewing with venation as in gardineri but vein M interstitial or apical to vein cu-v. Claws and tibial spurs normal.

Metasomal terga as in gardineri except punctures slightly smaller and surfaces shinier, unshagreened. Pygidial plate as in gardineri but apex broader and median longitudinal ridge longer. Sterna 2-5 as in gardineri but shinier, unshagreened.

VESTITURE. Generally white to pale ochraceous as in gardineri, with the following differences: tergal distal pale bands white; scopa. hairs white; pollen collecting hairs distributed as in gardineri but propodeal corbicula with internal hairs throughout or in anterior half or more.

MALE. MEASUREMENTS AND RATIOS. N=20; length, 8-10 mm; width, 2-3 mm; wing length, M= 2.97 0.119 mm; FL/FW, = 1.05 0.008; FS1/FS2, M = 2.15 0.048.

INTEGUMENTAL COLOR. Black except as follows: mandible with apical third rufescent, often basal triangle with a small yellow maculae (about one-third of specimens); clypeus yellow except reddish-brown apical margin and dark maculae mesad and below tentorial pits; parocular area with large yellow macula extending up to level of posterior of margin of clypeus and usually beyond, rounded above; flagellar segments 2-11 brown below; tegulae translucent, reddish-brown; wing membranes hyaline, veins dark reddish-brown; terga 1-5 narrowly hyaline apically, colorless, rufescent just basad of hyaline margins; sterna 2-5 narrowly hyaline apically, dark rufescent basally; sternum 6 with reflexed margin testaceous to translucent brown; distitarsi dark rufescent; tibial spurs pale yellow.

STRUCTURE. Antennae short, extending back to middle of tegulae in repose; scape length equals about first two and one-third flagellar segments or slightly less; flagellar segment 1 equal to or slightly shorter than segments 2 plus 3; segment 2 distinctly shorter than 3 and 3 shorter than segment 4; segment 4 quadrate, segments 5-11 longer than broad. Eye about three and one-third times as long as broad, inner margins strongly converging towards mandibles. Malar space, mandible and galea as in gardineri. Maxillary palpus as in gardineri but segmental ratio about 1.0:0.8:0.7:0.6:0.6:.07. Labial palpus as in gardineri but segmental ratio about 1.9:1.0:0.9:1.0. Labral process as in gardineri. Clypeus as in Female but median impunctate area often absent and punctures often slightly smaller and sparser. Supraclypeal and genal areas, vertex and face (above antennal fossae as in female.

Thoracic structure and sculpturing as in female except as follows: propodeal lateral surface with abundant punctures in dorsal half or more, surface shiny; mesepisternal punctures more crowded. Metasomal terga 1-5 like female terga 1-4. Pseudopygidial area well developed, almost half as broad as long, apex rounded. Sterna 2-5 sculptured as in female. Sternum 6 with apical margin reflexed as in gardineri.

Genitalia and sterna 7 and 8 (Figs. 267-271) similar to those gardineri but note the following differences: penis valves with tips bulbous; gonoforceps more pointed with inner-dorsal ridge more developed; sternum 8 with neck region less broadened in basal half, tip broader and entire.

VESTITURE. Generally as in female with the following differences: terga 1-5 with apical pale fasciae; sterna 2-5 with well-developed, suberect to decumbent, subapical fimbriae as in gardineri.

TYPE MATERIAL. The female holotype (USNM No. 59,273), was collected at Riverside, California, October 13, 1928, on Isocoma vernonioides by P. H. Timberlake.

DISTRIBUTION. This bee is known only from California. It has been collected from July 20th through November 6th, but chiefly in September and October. In addition to the holotype, 150 females and 50 males have been examined from the localities listed below: CALIFORNIA: Antioch; Bishop (6 miles N.), Mono Co.; Bodfish; Fort Tejon; Hemit Valley, San Jacinto Mts., Riverside Co.; Keen Camp (3 miles E.), Riverside Co.; Mission Valley; Morango Valley; Naples; Ocean Side, San Diego Co.; Pine Meadow, San Jacinto Mts., Riverside Co.; Red Rock Canyon, Kern Co.; Riverside; San Diego; Seal Beach, Orange Co.; Sonoma Co.; Turlock; Walker Pass, Kern Co.; Warner Springs; Yucca Valley, San Bernardino Co.

FLORAL RECORDS. Andrena isocomae is an oligolege of plants of the family Compositae and seems to prefer pollen from Gutierrezia, Isocoma and Heterotheca, in that order. Flowers from which A. isocomae has been collected are listed below.

Eriogonum sp., Gaillardia sp., Gutierrezia sp., C. californica, G. lucida, G. sarothrae, Heterotheca grandiflora, Isocoma sp., I. vernonioides, Senecio douglasii, Solidago sp.

Scientific source:

Andrena (Pterandrena) isocomae Timberlake, 1951, Proc. United Slates Nat. Mus., vol. 101, pp. 378-380.

Supported by

Hosts · map
FamilyScientific name @ source (records)
Asteraceae  Gutierrezia californica @ UCRC_ENT (7)

Gutierrezia microcephala @ UCRC_ENT (10)

Gutierrezia sarothrae @ UCRC_ENT (1)

Isocoma menziesii @ UCRC_ENT (3)

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Updated: 2023-09-29 17:39:22 gmt
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