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Andrena timberlakei Cockerell, 1929
Life   Insecta   Hymenoptera   Apoidea   Andrenidae   Andrena
Subgenus: Derandrena

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Reprinted with permission from the University of Nebraska State Museum from: Ribble, D. W. 1968. Revisions of two subgenera of Andrena, Micrandrena Ashmead and Derandrena new subgenus (Hymenoptera: Apoidea). Bulletin of the University of Nebraska State Museum 8: 1-124.

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Andrena timberlakei is a very unusual little bee and has diverged much from the vandykei line in a few characteristics. The female has hooked hairs on the mouthparts (prementum, glossa, labial palpus and galea) and a short maxillary palpus. The mouthparts are very unusual for Andrena and unlike any in the vandykei group. The mouthparts are extremely similar to Scoliandrena, an unrelated subgenus containing few species (probably two). Otherwise the female is much like californiensis (and is often collected with it) but lacks the plumose hairs along the anterior margin of the propodeal corbicula of californiensis. The male of timberlakei is apparently the only male Andrena with large facial foveae. Aside from these striking differences (mouthparts and foveae) and a few other minor ones (see description) timberlakei is much like other bees of the vandykei group (especially californiensis). Andrena timberlakei is clearly a member of the vandykei group and should not be separated from its relatives because it has acquired specialized female mouthparts and distinct male foveae.

The descriptions below are based mainly on a male (February 28, 1928) and a female (March 28, 1929, Puente Hills, Los Angeles Co.) which agree with the data given for the type series except as indicated. A total of 114 specimens of timberlakei were examined during this study.

FEMALE. MEASUREMENTS AND RATIOS. Length, 5.6 mm; width of mesothorax, 1.7 mm; wing length from tegula, 4.0 mm; facial length/width, 1.00; foveal length/width, 3.33.

INTEGUMENTAL COLOR. Dark brown to brown except: flagellum pale orange-brown below; terga and sterna with wide amber apices and blackened areas; color otherwise as in vandykei.

STRUCTURE. Antenna reaching slightly past tegula; scape reaching to within two ocellar distances of middle ocellus, as long as flagellar segments 1-4; segment 3 not tapered; ultimate segment not quite twice as long as broad; mandible and submandibular tooth normal for Andrena, not sharply pointed; galea not expanded below palpus, slender, both margins curving downward, tapering to narrowly rounded apex, with reticular shagreening, hooked hairs along margin and on surface, apical hairs nearly straight; maxillary palpus with segments in ratio of about 1.2:2.0:1.0:1.0:1.2:1.5, palpus atrophied, much shorter than galea, segments 1-3 not tapered; labial palpus with segments in ratio of about 1.4:1.0:1.0:1.7; labrum about one and three-fourths times as wide as long; process large, two-thirds as wide as entire labrum; clypeus with punctures close in center; genal area in side view as wide as eye; facial fovea dorsally nearly as wide as eye, inner margin not widely separated from eye below; outer margin tapering to narrower point than in vandykei.

Mesosoma as in vandykei except: pronotum with suture at base of posterior pronotal lobe ending below humeral angle, humeral angle strong, abruptly elevated above dorsal surface of pronotum, forming slight crease running across base of angle; scutellum shiny, unshagreened in center; propodeum with enclosure not becoming granular towards base; hind tibia slightly widened, half again as wide as basitarsus; claws with minute tooth on inner margin; anterior tibial spur with serrate part half as long as entire spur; wings with pterostigma large, nearly twice as large as prestigma; first transverse cubital vein ending about three vein widths from pterostigma.

Mesosoma as in vandykei.

VESTITURE. Hairs as in vandykei except: fovea, dorsum of thorax, apex of hind femur, base of hind tibia, tip of abdomen with amber hairs, other leg hairs white; hairs on dorsum of thorax short, with many branches, giving thorax a moss-like appearance; apical fasciae on terga 1-4, reduced to a few hairs on tergum 1, incomplete on 2 and 3, complete on 4; tibial scopa with anterior-most hairs much curved posteriorly.

MALE. MEASUREMENTS AND RATIOS. Length, 4.6 mm; width of mesothorax, 1.2 mm; wing length from tegula, 3.5 mm; facial length/width, 0.83; flagellar segment 1/segment 2, 1.30.

INTEGUMENTAL COLOR. Red-brown to brown except: clypeus nearly entirely yellow with two large lateral hyaline spots; color otherwise as in timberlakei female.

STRUCTURE. Head as in vandykei except: antenna reaching to propodeum; scape reaching to within two ocellar distances of middle ocellus; segment 1 one-third longer than 2, slightly longer than 3; mandible slightly bent in middle, less sharply pointed than in vandykei; galea as in female except without hooked hairs, straight hairs along outer margin; maxillary palpus with segments in ratio of about 2.5:4.0:2.0:1.0:1.5:3.5, palpus slightly longer than galea, segments slightly tapered; labial palpus with segments in ratio of about 2.7:1.0:1.3:2.3; labrum one-third wider than long; clypeus three and one-half times as broad as long, protruding beyond lower margin of eye by half width of eye in lateral view, punctures indistinct in center; genal area in lateral view slightly wider than eye, rounded posteriorly, projection at base of mandible tooth-like; vertex more elevated behind ocelli than in vandykei, between ocelli and eye surface much depressed, containing large, oval fovea.

Mesosoma as in vandykei except: suture extending vertically from leg base ending below humeral angle; apex of anterior tibial spur shorter than in female timberlakei.

Metasoma as in vandykei except sternum 6 emarginate apically, flexed downward medially, flexed part with uneven margin.

Sternum 7 deeply notched at apex, producing two large rounded processes, each process bearing few setae, sternum unshagreened (fig. 108). Sternum 8 (fig. 109) very similar to vandykei except slightly different in outline. Gonocoxite relatively slender, bent downward; gonoforceps greatly expanded near middle, dorsal surface with many branched setae; dorsal lobes long, narrow at apex. Penis valve slender, bent downward, apex expanded, slightly expanded medially (figs. 105-107).

VESTITURE. Hairs as in vandykei except most hairs white, facial fovea chocolate brown.

TYPE MATERIAL. Holotype male, number of paratypes not given but at least 1 female, Riverside, California, March 3 and 5, 1929, P. H. Timberlake, on Cryptanthe [sic] intermedia. No specimens were located which bear these dates. However, a male (USNM, no. 55308) is considered to be the holotype, because it bears the correct data, except for the date which is March 2. This specimen also carries a Cockerell label bearing the word type (Cockerell usually indicated holotypes in this manner). The information on the dates in the original publication is therefore considered a lapsus calami. Dr. Krombein kindly examined the holotype and proposed the action taken above. No other specimens of timberlakei examined appear to belong to the type series.

VARIATION. The male terminalia exhibit extensive variation. Males from the northern half of the range have the apical part of the penis valve shortened and medially the penis valve is expanded in lateral view. Sometimes there is a corresponding shortening of the gonoforceps. Other types of variation which appear not to be geographic are: the penis valve in dorsal view can be wider or narrower than drawn (fig. 105); the dorsal lobes of the gonocoxite vary slightly in shape; sternum eight at times lacks the expanded apex and may be wider medially than in figure 109. These variations in male terminalia do not warrant naming because there is no corresponding variation in external characters and seemingly all males have dissimilar terminalia. The latter would make splitting timberlakei into additional species (or subspecies) very difficult. Rather, this variation indicates that timberlakei (a species that has already undergone a considerable divergence from the vandykei line) is in the process of rapid evolutionary change in these terminal structures they have not yet become canalized.

The males exhibit variation in size (2.9-4.2 mm, wing length from tegula) and are at times smaller than any other species of North American Andrena (and approach the minimum size of any bee genus).

In the female the labral process varies in shape; it may be evenly rounded from side to side or subtriangular in shape. The apical abdominal fasciae vary somewhat in length.

One specimen appears to be an intersex. It is a female in most respects but has a male-like head (however, the clypeus is not yellow). This specimen does not appear to be stylopized.

Scientific source:

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Updated: 2024-04-15 17:07:14 gmt
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