Lasioglossum pacificum (Cockerell 1898)

Lasioglossum pacificum (Cockerell)

Halictus pacificus Cockerell, 1898c:50–51 [female, misidentified male, key].—Vachal, 1904:472 [female].—Crawford, 1906:301 [locality record].

Lasioglossum pacificum.—Michener, 1951:1107 [Nearctic catalog].—Linsley and MacSwain, 1959:22 [flight records, association with Ranunculus].—Moldenke and Neff, 1974:54 [locality and flower records].—Hurd, 1979:1957 [Nearctic catalog].

TYPE MATERIAL.—In his original description of Halictus pacificus, Cockerell did not designate a holotype. The lectotype female, designated herein, is labeled

HOLOTYPE [on red label/Olympia [Thurston County], Wash.[ington]/6 [June] 24 [18]95 [handwritten in pencil]/H.[alictus] pacificus. Ckll. [Cockerell] n. sp. [new species] [handwritten by Cockerell/LECTOTYPE Halictus pacificus Cockerell des.[ignated by] McGinley [on red label].

The specimen, deposited in the California Academy of Sciences in San Francisco, has many body hairs soiled or matted but otherwise is in good condition.

Cockerell mentions that the male of H. pacificus has the “apical portion of clypeus yellow” and the “hind tibiae at both ends, and all the tarsi, yellow,” which is clearly a misassociation, as both the clypeus and tarsi of L. pacificum are never yellow. The male that Cockerell describes is possibly that of L. titusi, which was described by Crawford, four years later in 1902.

DISTRIBUTION (Figure 554).—Lasioglossum pacificum is presently known from the extreme southwestern corner of British Columbia, including Vancouver Island and south through the coastal and subcoastal areas of Oregon, Washington, and California to Santa Barbara County.

DIAGNOSIS.—The strongly and regularly striate propodeal dorsal surface (Figure 559) will distinguish Lasioglossum pacificum from other Lasioglossum species except L. leucozonium, L. zonulum, L. sisymbrii, and L. timberlakei. Lasioglossum leucozonium and L. zonulum differ in having relatively longer heads (Figures 492, 555, 734) and in having a conspicuously short propodeal dorsal surface, which is only slightly longer than the metanotum (Figures 496, 738; propodeal surface much longer than the metanotum in L. pacificum and most other species). Of the two species, only L. zonulum occurs sympatrically with L. pacificum and is further differentiated by its sharply pointed lateral pronotal angles (Figure 141; pronotal angles broadly obtuse in L. pacificum). The unique first tergal basal hair band (Figure 132) and the pale, translucent tegulae will differentiate L. sisymbrii. Lasioglossum olympiae is very similar but can be distinguished by its sharply truncated posterior propodeal margin (Figure 536; slightly bowed posteriad in L. pacificum, Figure 559), slightly different head shape (Figure 532 vs. Figure 555) and the smooth, relatively polished area immediately dorso-anteriad of the middle coxa (Figure 146; area striolate and dull in L. pacificum, Figure 147). The most similar species to L. pacificum is L. timberlakei (especially the dark form), which can be differentiated by its weak, obscure mesoscutal punctation (Figure 622 vs. Figure 560) and the short, dense pubescence along the posterolateral margin of the mesoscutum (hairs elongate in L. pacificum).

The presence of elongate hair tufts on the lateral edges of sternum V (Figure 561) will differentiate the males of L. pacificum from those of other Lasioglossum species except L. sisymbrii and L. timberlakei. These species also share the lack of a clypeal maculation and have the dorsal propodeal surface strongly striate to rugose. Lasioglossum sisymbrii males have a basal white hair band on tergum I as in Figure 132 (absent in L. pacificum) and pale, translucent tegulae (dark brown in L. pacificum). Lasioglossum pacificum males differ from those of L. timberlakei in having well-developed mesoscutal punctation (punctures sparse and obscurely developed in the latter two species). Furthermore, the vestiture of sternum V of both species differs slightly as illustrated in Figures 561, 562.

DESCRIPTION.—FEMALE: (1) Length 8.4–10.8 mm (x = 9.7, n= 15); (2) wing length 2.4–2.8 mm (x = 2.7, n = 15); (3) abdominal width 2.8–3.4 mm (x = 3.2, n = 15).

Structure: (4) Head short (Figure 555; length/width ratio 0.79–0.89, x = 0.85, n = 15). (7) Supraclypeal area evenly rounded. (8) weakly protuberant. (9) Clypeus projecting approximately 0.70 of its length below lower margin of eyes; (10) surface without median longitudinal sulcation. (14) Distance between lateral ocelli subequal to distance between lateral ocellus and eye. (23) Flagellomere 1 subequal in length to 2 along dorsal surface. Labrum as in Figure 557; (27) distal keel narrow in frontal view, lateral edges slightly bowed; (28) distal lateral projections virtually absent, evident as obscure swellings; (29) fimbrial setae acutely pointed.

(32) Pronotal lateral angle broadly obtuse; (33) pronotal lateral ridge incomplete, broadly interrupted by oblique lateral sulcus; (34) lower portion of lateral ridge inconspicuous, broadly rounded. (35) Mesoscutal lip rounded, not bilobed, (36) moderately elevated from pronotum. (40) Dorsal surface of propodeum about 0.65 the length of scutellum and subequal to metanotum in length, (41) not depressed centrally, (42) posterior margin truncated (slightly bowed posteriad); (43) propodeal triangle weakly defined laterally; (44) lateral carinae completely encircling posterior surface. (45) Tibial spur as in Figure 44.

(46) Lateral edge of metasomal tergum II very weakly sinuate, posterior two-thirds shallowly concave.

Sculpture: (47) Face shiny, (48) densely punctate below ocelli, punctures contiguous, becoming larger and less dense near antennae. (51) Supraclypeal area extremely granulate; (52) punctures separated by their width laterally, slightly less dense centrally. (53) Clypeus granulate basally and medially to apex, apicolateral areas polished; (54) punctures obscure, separated by less than their width basally, becoming well defined and less dense apically. (56) Mesoscutum shiny; (57) punctation as in Figure 560, punctures 1–2 times their width apart laterally and anteriorly, 2–4 times their width apart centrally. (58) Scutellum with conspicuous impunctate areas adjacent to median line. (63) Dorsal surface of propodeum (Figure 559) strongly and completely striate to porcate, striae evenly spaced with very few obscure transverse rugulae; (64) surface smooth, not alveolated. (65) Metasomal tergum I shiny; (66) punctation extremely fine, sparse posteriorly, punctures 2–3 times their width apart, punctures scattered anteriorly with large impunctate areas.

Coloration: (71) Wing membrane nearly hyaline, very lightly pigmented.

Vestiture: (74) Pubescence of head golden. (75) Pubescence of thorax golden; (76) mesoscutal hairs moderately dense, very conspicuously plumose. (77) Hind tibial hairs concolorous, golden. (78) Anterior hairs of metasomal tergum I and (79) basal hair bands of terga II–IV yellowish white. (80) Acarinarium absent, elongate hairs scattered over anterior surface of tergum I. (81) Unlike other species, basal hair band of tergum II interrupted medially.

MALE: Similar to female except as follows: (1) length 7.3–9.0 mm (x = 8.0, n = 15); (2) wing length 2.1–2.4 mm (x = 2.3, n = 15); (3) abdominal width 2.0–2.6 mm (x = 2.3, n = 15). (4) Head as in Figure 556 (length/width ratio 0.83–0.92, x = 0.87, n = 15). (5) Gena subequal to eye in width, (6) rounded, not produced posteriorly. (10) Clypeal surface broadly rounded, not flattened or depressed. Labrum as in Figure 558; (24) distal process very weakly developed, broadly rounded; (25) basal area rounded medially, not depressed; (26) basal lateral depressions absent. (30) Mandible very short, not reaching opposing clypeal angle. (53) Clypeus weakly granulate, shiny; (54) punctation nearly uniform throughout, punctures separated by 1–2 times their width. (68) Clypeal maculation absent. (69) Flagellum entirely dark to pale yellowish orange ventrally and contrasting with dark dorsum. (72) Tarsi dark, concolorous with tibiae.

Vestiture: Sternal vestiture as in Figure 561; (82) hairs on sternum IV short, adpressed, with noticeable hair fringe on posterior sternal edge; (83) sternum V with rounded hair fringe on posterior sternal edge, hairs becoming elongate laterally, forming conspicuous lateral tufts.

Terminalia: Sterna VII–VIII as in Figure 567; (85) sternum VIII without median process, distal edge of disc sharply truncated. Genitalia as in Figures 563–566; (86) gonobase moderately elongate; (87) gonostylus moderately elongate, robust, bluntly rounded; (89) retrorse membranous lobe extremely reduced, slender; (90) volsella with weakly developed lateral flange but lacking prominent lateral lobe.

FLIGHT RECORDS (Figure 568).—Lasioglossum pacificum females have been collected from February to late November, with most records from late May and June. Male records range from late June to early October, with a southwestern peak in early August and a northwestern peak in early September.

FLOWER RECORDS.—Females (41): Ranunculaceae 15%; Cruciferae 12.5%; Compositae 12.5%; Scrophulariaceae 12.5%; Umbelliferae 12.5%. Males (7): Compositae 88%; Convolvulaceae 12%. Total: 48 in 14 families, 22 genera as follows:

Achillea 1, 5; Anaphalis 1, 20; Angelica 2; Brassica 5; Chrysanthemum 1; Cichorium 1; Cicuta 1; Convolvulus 1; Cornus 1; *Heracleum 2(1); Iris 1; Myosotis 1; *Orthocarpus 4(4); Poa 1; * Potentilla 1(1); * Ranunculus 6(1); * Rhododendron 4(4); Rubus 1; * Salix 4(1); Scrophularia 1; Stellaria 1; Taraxacum 1.

SPECIMENS EXAMINED.—663 (541, 122).

CANADA. BRITISH COLUMBIA: Agassiz, Miracle Beach (near Oyster river), Mission City, Nanaimo Biology Station, Royal Oak, Saanich, Sooke, Vancouver, Victoria, Wellington.

UNITED STATES. CALIFORNIA: Alameda Co.; Contra Costa Co.: Fish Ranch Road, Orinda (4 mi NW), Walnut Creek; Humboldt Co.; Marin Co.; Mendocino Co.; Monterey Co.; San Benito Co.: Prunedale, 8 mi N; San Francisco Co.; San Luis Obispo Co.: Cambria, Grover City, Ocean, 3 mi S; San Mateo Co.; Santa Barbara Co.: Goleta, Jalama Beach, Santa Ynez River (Highway 101); Santa Clara Co.: San Jose, Palo Alto; Santa Cruz Co.; Sonoma Co.: Mesa Grande, Pitkin Marsh, Plantation (4 mi W), Valley Ford, 2 mi SE; Trinity Co.: Weaverville, 47 mi W. OREGON: Benton Co.: Corvallis; Clackamas Co.: Oswego; Clatsop Co.: Olney; Columbia Co.: St. Helens-Scappoose: Curry Co.: Brookings, Pistol River; Douglas Co.: Roseburg (7 mi NW), Winchester Bay; Jackson Co.: Butte Falls (10 mi SE), Griffin Creek; Lane Co.: Eugene; Lincoln Co.; Multnomah Co.: Portland; Polk Co.: Monmouth; Wasco Co.: The Dalles; Washington Co.: Forest Grove; Yamhill Co.: Sheridan. WASHINGTON: Clark Co.: Vancouver; Island Co.: Coupeville; King Co.: Northbend, Seattle; Kitsap Co.: Illahee, Seabeck; Pacific Co.; Pierce Co.: Fort Lewis, Pleasant Valley; Thurston Co.: Olympia.

Lasioglossum pacificum is a species of sweat bee in the family Halictidae.