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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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This small species with black integument can be recognized in the female sex by the lack of pronotal humeral angles and dorsolateral ridges, the short labral process, and the relatively strongly punctate mesoscutum. The male of escondida has the clypeus black, lacks pronotal humeral angles, and has well-formed, sternal, subapical fimbriae of relatively long, dense, straight hair
FEMALE: MEASUREMENTS AND RATIOS. N = 12; length, 8.0-9.5 mm; width, 2.0-2.5 mm; WL, M = 2.61 ± 0.189 mm; FL/FW, M = 0.95 ± 0.029; FOVL/FOVW, M = 2.60 ± 0.157.
INTEGUMENTAL COLOR. Black except as follows: mandible with apical third rufescent; flagellum with last several segments reddened below; wing membranes hyaline, veins red to reddish brown; metasomal terga with apices narrowly hyaline, becoming darker towards base; tibial spurs yellow.
STRUCTURE. Antennal scape as long as first three and one-half flagellar segments or slightly more; flagellar segment 1 as long as segments 2 plus 3, which are equal in length; segments 5-7 about as long as broad. Eyes each about four times as long as broad, inner margins parallel. Mandibles short, overlapping when closed by one fourth or less of mandibular length; with subapical tooth. Malar space short, linear. Galea pointed, outer margin gently concave in apical half; surface dulled by fine tessellation. Maxillary palpus relatively short, when extended surpasses galea by about last segment, segmental ratio about as 0.7:1.0:0.9:0.6:0.5:0.6. Labial palpus normal, segmental ratio about as 1.0:0.6:0.3:0.5. Labral process short, entire, about three times as long as broad, not emarginate apically or only extremely shallowly so; shiny; labrum apical to process at least as long as process, flat, shagreened. Clypeus short, gently rounded from side to side, surface dull, tessellate with sparse, indistinct punctures, which become crowded and more distinct in narrow apical band. Supraclypeal area dull, coarsely tessellate. Face above antennal fossae with fine longitudinal rugulae and shagreening. Facial fovea extends to just below line across lower margins of antennal fossae, three times as long as broad; separated from lateral ocellus by about one ocellar diameter. Vertex above lateral ocellus short, equals less than one ocellar diameter. Genal area in profile equals about one and one-third times width of eye, surface dull, shagreened. Pronotum without humeral angles or lateral ridges, surface dull, shagreened.
Mesoscutum dull, finely tessellate, with punctures medially separated mostly by two or more puncture widths, near parapsidal lines and in anterior fifth or more; dorsal enclosure of propodeum finely punctatorugose basally, outside of enclosure tessellate with scattered obscure punctures; basal sulcus almost parallel-sided, short; dorsoposterior surface separated from lateral surfaces by distinct carinae. Pleurae dull, finely tessellate, punctures absent or obscure.
Metasomal tergum 1 tessellate, somewhat more finely so in apical area, with minute obscure punctures not much larger than tesserae, separated by two to four puncture widths. Terga 2-4 similarly sculptured, tergum 5 more densely punctate. Pygidial plate U-shaped, raised rim, if present, extremely narrow. Sterna 2-5 with basal areas finely tessellate, slightly shiny, with distinct punctures separated by half to two puncture widths.
VESTITURE. White to pale ochraceous except as follows: facial fovea with tomentum silvery white to entirely white in lower half and pale yellow to golden in upper half; terga 5 and 6 with mediobasal hairs dark ochraceous; inner surfaces of tarsi light yellow. Dorsal thoracic hairs long, mostly longer than width of flagellum. Tergum 2 with apical fascia of pale hairs interrupted medially by less than one-third width of tergum; terga 3 and 4 with complete apical pale fasciae. Tibial scopal hairs simple to weakly plumose; propodeal corbicula incomplete anteriorly with long internal hairs; trochanteral flocculus complete but relatively sparse.
MALE: MEASUREMENTS AND RATIOS. N = 16; length, 7-9 mm; width, 1.5-2.5 mm; WL M = 2.30 ± 0.633 mm; FL/PW, M = 1.02 ± 0.008; FS 1/FS2, M = 2.06± 0.043.
INTEGUMENTAL COLOR. As in female except terga 2-5 with apical areas more broadly hyaline apically.
STRUCTURE. Antennae short, female-like; flagellar segment 1 twice as long as segment or slightly longer, segment2 usually slightly longer than 3, broader than long, segments 1-7 about as long as broad; scape length as in female. Eyes each almost four times as long as broad, inner margins diverging towards vertex. Mandibles apposite, short, with subapical tooth. Galeae as in female. Maxillary palpus as in female but ratio about as 10,7:1.0:0.6:0.6:0.5:0.6. Labial palpus as in female but ratio about as 1.0:0.5:0.4:0.5. Labral process short, more than twice as broad as long, apical margin gently concave, surface shiny; labrum apical to process about as long as process, finely shagreened. Clypeus sculptured as in female but punctures slightly more distinct and denser, separated mostly by one in two puncture widths. Supraclypeal area, face above antennal fossae, and vertex and genal area as in female.
Pronotum as in female. Thoracic sculpturing as in female except as follows: anterior fifth of mesoscutum with punctures sparse, mostly separated by two puncture widths; propodeum with dorsoposterior and lateral surfaces separated by weak carinae extending up from below to about half the length of propodeum.
Metasomal terga 1-6 sculptured ;is in female terga 1-5 hut surfaces slightly shinier. Sterna as in female. Sterna 7 and 8 as in Figs. 20 and 21. Note that sternum 7 has apical lobes evenly rounded on external edges and median emargination narrow. Sternum 8 has apex not at all emarginate or extremely shallowly so, area of broad, flattened hairs covering half or more of neck.
VESTITURE. Generally white to pale ochraceous but inner surfaces of tarsi pale yellow. Metasomal terga 2-5 with weak short apical pale fasciae, those on terga 2 and 3 interrupted medially and often on tergum 4. Sterna 2-5 with distinct pale subapical fimbriae of long, almost straight, dense, plumose, white hairs.
TYPE MATERIAL. The holotype male of escondida (CAS 15,331) was collected at Rancho Escondido, Santa Catalina Island, Los Angeles Co., California, from flowers of Encelia californica, March 31, 1938, by W.P. Cockerell.
DISTRIBUTION. Andrena escondida is known (Fig. 1) from Yolo County in central California south to San Diego County. It has been collected from March 2 through May 12, but chiefly in March and April. A total of 12 females and 16 males from localities listed below (including localities cited in the literature) were studied.
CALIFORNIA. ALAMEDA CO.: Midway. FRESNO CO.: Big Panoche Creek (Fresno-San Benito County line). KERN CO. LOS ANGELES CO.: Gorman (5 mi. S); Los Angeles; Santa Catalina Island. SAN DIEGO CO.: Escondido. SAN JOAQUIN CO.; Hospital Canyon; Tracy (6 mi. W). SANTA BARBARA CO.: Cachuma Canyon (2 mi. NW). SOLANO CO.: Dixon (8 and 9 mi. S); Putah Canyon. STANISLAUS CO.: Modesto. TULARE CO.: Visalia. YOLO CO.: Davis.
FLORAL RECORDS. Andrena escondida should be considered as an oligolege of composites of the genus Layia. It has been collected from the plants listed below (including records in the literature).
Brassica sp., Calochortus catalinae, Encelia californica, Lasthenia chrysostoma, Layia sp., L. chrysanthemoides, Plagiobothrys sp.
Andrena escondida Cockerell, 1938, Ann. Mag. Nat. Hist., ser. 11, 2:146.
Andrena (Hesperandrena} escondida: Timberlake, 1949, in Lanham, California Univ. Publ. Ent., 8:208; Timberlake, 1951, Proc. United States Nat. Mus., 101:386 Rust, Menke and Miller, 1985, Entomology of the California Channel Islands: Proc. 1st Symp., San Diego, California, Dec. 1981, p. 42.
Updated: 2021-05-12 03:03:13 gmt