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Andrena torulosa LaBerge, 1971
Andrena (Nemandrena) torulosa LaBerge, 1971

Life   Insecta   Hymenoptera   Apoidea   Andrenidae   Andrena
Subgenus: Melandrena

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Reprinted with permission of the Pan-Pacific Entomologist from: LaBerge, W. E. 1971a. A new subgenus of Andrena found in California and Oregon (Hymenoptera: Apoidea). Pan-Pacific Entomologist 47: 47-57.

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This small gray species can be told from the other two species of Nemandrena by the presence of a strongly developed humeral angle and dorsoventral ridge on the pronotum in both sexes. If this character were overlooked, A. torulosa would be extremely similar to A. crudeni whose description follows, but differs from A. subnigripes by the paler vestiture of the metasoma and legs. So similar are A. torulosa and A. crudeni that one wonders whether or not the complicated-looking, pronotal character difference could not be produced by a single Mendelian locus with a dominant gene producing one or the other condition. No intermediates have been found and there seems to be complete geographic separation between the two species. It is hoped that giving both forms specific status will keep the problem from becoming lost in the literature.

FEMALE. MEASUREMENTS AND RATIOS. N = 20; length, 9-11 mm; width, 3.0-3.5 mm; wing length, M = 3.65 0.110 mm; FL/FW, M = 0.88 0.003; FOVL/FOVW, M = 3.17 0.050.

INTEGUMENTAL COLOR. Black except as follows; tips of mandibles rufescent; flagellar segments 3- or 4-10 dark brown below; wing membranes hyaline, veins dark reddish-brown; terga 2-4 with apical areas slightly hyaline; sterna 2-5 with apical areas hyaline; distitarsi slightly rufescent; tibial spurs testaceous.

STRUCTURE. Antennal scape length equal to flagellar segments 1-3 plus three-fourths of segment 4; flagellar segment 1 as long as segments 2 plus 3 plus three-fourths of 4, segment 2 about equal in length to 3 and each shorter than 4, segments 2 and 3 about as long as broad or shorter, 4-10 longer than broad. Eyes each about four times as long as broad, inner margins parallel. Malar space linear, width of base of mandible equals about 5.5 times minimum length of malar space. Mandible short, in repose extending beyond middle of labrum by about one-fifth its length. Galea dull, tessellate, short, extremely narrow and pointed. Maxillary palpus extends beyond tip of galea by last two segments; segmental ratio about 1.0:1.0:1.0:0.8:0.5:0.7. Labial palpus with first segment slightly curved; segmental ratio about 1.0:0.7:0.5:0.6. Labral process triangular, depressed medially near apex and with a small median protuberance just basad of depression or with a distinct median longitudinal rugula with a small lateral concavity on either side near apex (holotype of first type); labrum apical to process with a strong transverse shiny sulcus. Clypeus relatively flat, with a distinct median subapical shiny boss, lateral to boss gibbous subapically, remainder with large, crowded punctures but extremely shallow and obscured by fine dense tessellation. Supraclypeal area sculptured like clypeus but punctures smaller. Genal area in profile as broad as one and one-half times eye width, surface dulled by minute, relatively sparse punctures and coarse reticular shagreening. Vertex short, above lateral ocellus equal to one ocellar diameter or slightly more, surface opaque, dulled by dense regular tessellation and small sparse punctures. Face above antennae with tine longitudinal rugae, interrugal spaces dulled by fine reticular shagreening. Facial fovea short, narrow, extends to just below lower margins antennal sockets, separated from lateral ocellus by one ocellar diameter or more, well separated from margin of compound eye.

Pronotum with well-formed humeral angle, triangular in lateral view, and dorsoventral ridge not crossed by an impressed oblique suture; surface tessellate, area behind dorsoventral ridge slightly roughened. Mesoscutum between parapsidal lines except in anterior third with extremely fine, close-set, longitudinal rugulae, with minute obscure punctures separated mostly by one to two puncture widths or more, surface opaque, dulled by fine regular tessellation. Scutellum similar but without rugulae or these short and evanescent. Metanotum dulled by close-set: minute punctures and dense tessellation. Propodeum with dorsal enclosure smooth, tessellate, with a few extremely short rugulae at base; dorsolateral and posterior surfaces with distinct sparse punctures and surface coarsely tessellate; corbicular surface coarsely tessellate, punctures extremely sparse. Mesepisternum with fine shallow punctures obscured by fine dense tessellation. Pterostigma about as broad; as from inner margin prestigma to anterior wing margin; vein 1st m-cu meets second submarginal cell at or before middle of cell.

Metasomal terga with apical areas indistinct, basal areas with small punctures separated mostly by one to two puncture widths, more crowded on terga 2 and Ss than on 1 and 4, apical area punctures sparse; punctures obscured by coarse, a irregularly and finely reticulate shagreening. Pygidial plate V-shaped with rounded apex, without raised internal triangular area, with strongly curved rows of close-set coarse punctures (unless worn). Sterna 2-5 with narrow impunctate apical areas, s basal areas with crowded punctures in apical halves, impunctate basally, surfaces moderately dulled by fine reticular shagreening.

VESTITURE. Generally cinereous but vertex and facial foveae with brown hairs, terga 5 and 6 brown medially, tarsi with outer surfaces at least partly brown, hind tibiae with scopal hairs below basitibial plates and along posterior border brown, and fore and middle tibiae with outer surfaces brown at least in part. Fore coxae (and to a lesser degree middle coxae) with long, stiff, simple hairs. Terga without apical pale fasciae; sterna 2-5 with short hairs in basal areas and subapical fringes of extremely long, plumose hairs. Propodeal corbicula with moderately long, plumose hairs anteriorly, with abundant internal long simple hairs; trochanteral flocculus complete; tibial scopal hairs simple, relatively short (but along posterior margin at least as long as median width of tibia).

MALE. MEASUREMENTS AND RATIOS. N = 16; length, 8-10 nun; width, 2-3 nun; wing length, M = 3.43 0.196 mm; FL/FW, M = 0.81 0.004; FS1/FS2, M = 2.33 0.052. INTEGUMENTAL COLOR. Black except as follows: mandibles with tips rufescent; flagellar segments 2- or 3-11 reddish-brown to dark brown below; wing membranes hyaline, colorless, veins dark reddish-brown; terga 2-5 with apical areas slightly translucent; sterna 2-5 with apical areas hyaline or rufescent; distitarsi rufescent; tibial spurs testaceous.

STRUCTURE. Antennae moderately long, in repose reaching to metanotum; scape length equals first two and one-half flagellar segments or slightly more; flagellar segment 2 distinctly shorter than 3 and shorter than broad, segments 3-11 longer :than broad. Eyes each about three and one-third times as long as broad, inner margins parallel. Malar space and galeae as in female. Mandible as in female but slightly longer. Maxillary palpus as in female but segmental ratio about .0.7:1.0:0.9:0.8:0.7:0.7. Labial palpus as in female but ratio about 1.0:0.5:0.6:0.5. Labral process triangular with a prominent median horn half as long as length lot process rising from surface subapically; apical part of labrum not strongly :'silicate as in female. Clypeus broad, relatively flat with a prominent median shiny elevated boss, surface elsewhere dulled by crowded, extremely shallow punctures and fine, dense tessellation. Supraclypeal area, genal area, vertex and face above antennae as in female except genal area slightly broader, face above antennae with rugae weak especially near ocelli and vertex somewhat taller.

Thoracic sculpturing as in female except mesoscutum with rugulae scarcely visible except in posterior declivity, much finer than in female and scutellum without evident rugulae. Wing venation as in female. Tergal sculpturing as in female except basal area punctures sparser (separated mostly by two to four puncture widths) and apical areas of terga 2-5 shinier, shagreening finer. Sterna 2-5 as in female but punctures extremely sparse. Sternum 6 with a broad, very shallow, apical emargination, subapically with a median, slightly protuberant, triangular knob; medially impunctate and dull to moderately shiny.

Terminalia as figured (Figs. 1-5), note the following: falcate apical processes of gonocoxites; shape of volsellae; sternum 8 with apical area with short stout pointed hairs medially.

VESTITURE. Generally white to cinereous; clypeus with thick beard; terga without pale apical fasciae; sterna 2-5 without distinct subapical fimbriae but with a single transverse row of subapical, extremely long, plumose hairs (longest laterally).

Scientific source:

Supported by

Hosts · map
FamilyScientific name @ source (records)
Boraginaceae  Nemophila menziesii @ AMNH_BEE (1)
Hydrophyllaceae  Nemophila menziesii @ BBSL (1)
Limnanthaceae  Limnanthes douglasii @ BBSL (2); BMEC_ENT (52)

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Updated: 2023-09-29 16:04:13 gmt
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