Lasioglossum (Hemihalictus) swenki (Crawford 1906)

Gibbs, Jason, Packer, Laurence, Dumesh, Sheila & Danforth, Bryan N., 2013, Revision and reclassification of <i> Lasioglossum </ i> (<i> Evylaeus </ i>), <i> L. </ i> (<i> Hemihalictus </ i>) and <i> L. </ i> (<i> Sphecodogastra </ i>) in eastern North America (Hymenoptera: Apoidea: Halictidae), Zootaxa 3672 (1), pp. 1-116 : 60-68

Lasioglossum (Hemihalictus) swenki (Crawford 1906)

( Figs. 4K , 5K , 6K , 7K , 8K , 37B , 40 , 41 , 77C , 78A )

Halictus swenki Crawford 1906b, p. 275 (October)

Holotype. ♀ USA, Nebraska, Cuming Co., West Point , 15.vi.1905 on Rosa arkensena (L. Bruner, H.E. Smith) ; [ NMNH: 10454]. Examined by JG 2012.

(Labels read “West Pt Neb./June 15 ’05 [numbers handwritten]/On Rosa arkensena [handwritten]/L. Bruner & J. Smith [handwritten]/ Type No. 10454 [number handwritten on red label] U.S. N.M./ Halictus swenki ♀ Type Crawford [handwritten on black bordered label]”).

Evylaeus swenki (in Hurd 1979: catalogue; Moure & Hurd 1987: catalogue)

Halictus (Evylaeus) swenki (in Stevens 1920: ♂)

Lasioglossum (Evylaeus) swenki (in Michener 1951: catalogue)

Diagnosis. Female L. swenki can be recognised by the combination of pronotum sharply angled; mesoscutum imbricate, dull; hypoepimeral area finely punctate ( Fig. 78A ); and inner metatibial spur pectinate with five narrow teeth, basal tooth much longer than width of rachis ( Fig. 5K ). Lasioglossum swenki can be easily distinguished from all eastern species by the characters listed above, except L. fedorense . In L. fedorense the carina is more complete and extends anterior to the oblique sulcus. In L. fedorense , the hypoepimeral area is rugulose and impunctate ( Fig. 78B ). Some L. swenki females can be distinguished from L. fedorense by the colour of the metasoma, which is sometimes red-orange in some individuals of L. swenki ( Fig. 40 ), but in others the metasoma is brown ( Fig. 37B ). Specimens of L. swenki with a brown metasoma can be distinguished from L. fedorense by characters of the hypoepimeral area and pronotum described above.

Male L. swenki can be recognised by the combination of clypeus yellow, except for basolateral patch infused with brown ( Fig. 6K ); mandible elongate, reaching opposing mandible base (as in Fig. 6J ); scape yellow, distinctly longer than F2; gena narrower than eye; mesepisternum polished, shiny, with distinct, but fine, punctures; and metapostnotum rugulose (as in Fig. 77C ). They are most similar to L. fedorense and L. sopinci , which both have the gena wider than eye ( Figs. 16 , 38 ). Male L. fedorense also have the mesepisternum imbricate, dull with only shallow punctures. Male L. sopinci have the metapostnotum coarsely rugose (as in Fig. 77A ).

Redescription. FEMALE. Length 5.7–6.0 mm. Head length 1.63–1.93 mm. Head width 1.73–1.94 mm. Wing length 5.0– 5.2 mm. (n=7)

Colour. Head and mesosoma black. Antenna black, except ventral surface of flagellum reddish brown-orange. Tegula reddish brown-testaceous. Legs dark brown, except medio- and distitarsi reddish brown, inner protibial surface infused with reddish brown. Wing membrane hyaline, pale. Pterostigma pale yellow-testaceous. Metasomal terga orange-testaceous (sometimes brown with testaceous apical borders), except T5–T6 dark brown basally.

Structure. Head round (L/W ratio = 0.98–1.01). Clypeus 1/2–2/3 below suborbital line. Eyes divergent below (UOD:LOD = 1.07–1.19). Gena narrower than eye. Ocelli normal. Pronotal ridge sharply angled. Protibial spur with serrations subequal to width of malus. Inner metatibial spur pectinate, teeth 5, basal teeth longer than width of rachis. Propodeal lateral carina not reaching dorsal margin, oblique carina absent.

Surface sculpture. Supraclypeal area imbricate; punctures fine, contiguous (i<d). Gena and postgena lineolate. Mesoscutum weakly imbricate-polished; doubly punctate, most punctures fine, dense laterally (i≤d), wellseparated between parapsidal lines (i=1–1.5d). Mesepisternum relatively smooth, polished, hypoepimeral area distinctly punctate (i≤d). Metapostnotum carinate-rugose, apical margin imbricate, rounded onto posterior propodeal surface. Propodeum imbricate-tessellate. Metasomal terga polished, apical impressed areas weakly coriarious; punctures dense throughout.

Pubescence. Head and mesosoma with sparse plumose hairs. Frons and paraocular area with tomentum. Mesoscutum lateral margins with tomentum. Mesepisternum and metepisternum with tomentum beneath erect plumose hairs. Metafemoral scopa with dense plumose hairs. Propodeum with tomentum beneath erect hairs. Metasomal terga with moderately dense apical fimbriae, continuous on T3–T4. T1 with sparse, erect plumose hairs. Metasomal sterna with mostly simple scopal hairs.

MALE. Length 5.4–6.6 mm. Head length 1.54–1.80 mm. Head width 1.60–1.88 mm. Wing length 4.4–5.1 mm. (n=6)

Colour. Head and mesosoma black. Clypeus yellow, except basolateral testaceous-brown patch. Mandible yellow. Labrum yellow. Antenna yellow, except dorsal surface of flagellum brown, scape infused with brown dorsally. Pronotal lobe yellow. Legs yellow-testaceous, except coxae, trochanters brown, outer surface of metatibia infused with brown. Wing membrane hyaline, pale. Pterostigma pale yellow-testaceous. Metasomal terga orangetestaceous, except T4–T6 brown basally, T1 anterior surface infused with brown (or entirely black-brown with testaceous apical margins).

Structure. Head wide (L/W ratio = 0.96–0.99). Clypeus ½ below suborbital line. Mandible long, reaching opposing mandibular base. Flagellomeres, except F1, moderately elongate, F2 subequal to F1 and pedicel combined. Eyes convergent below (UOD:LOD = 1.17–1.24). Gena subequal to eye in width. Pronotal ridge sharply angled. Propodeal lateral carina not reaching dorsal margin.

Surface sculpture. Supraclypeal area imbricate; punctures fine, dense (i≤d). Ocellocular area polished, distinctly punctate. Gena and postgena smooth, weakly imbricate. Mesoscutum polished; punctures fine, dense laterally (i≤d), well-separated between parapsidal lines (i=1–1.5d). Mesepisternum polished, densely punctate. Metapostnotum carinulate-rugulose, apical margin imbricate. Propodeum imbricate-tessellate. Metasomal terga polished; punctures, close basally, obscure on apical impressed areas.

Pubescence. Head and mesosoma with sparse plumose hairs. Frons and paraocular area with relatively dense tomentum. Mesoscutum lateral margin with tomentum. Mesepisternum and metepisternum with appressed tomentum below erect plumose hairs. Propodeum largely bare, with scattered plumose hairs. Metasomal terga with apical fimbriae sparse. Metasomal sterna with sparse, plumose hairs (1–1.5 OD).

Terminalia . As shown in Figs. 7K , 8K . Gonostylus large, round, with long, plumose hairs. Retrorse lobe long, narrow.

Taxonomic notes. Lasioglossum swenki has close affinities with L. fedorense and L. sopinci . There are two distinct colour forms of L. swenki in the eastern USA that occur in sympatry. The metasoma may be primarily ferruginous ( Fig. 40 ) or largely black-brown ( Fig. 37B ). The type series is of the red form. Intermediate colour forms have not been seen. Specimens of L. swenki occurring in Utah seem to be smaller and paler than more eastern specimens. Dark forms have been mistaken in the past for L. fedorense (e. g. Grundel et al. 2011), which occurs in sympatry in the sand-dunes of northern Indiana. These two species are very similar but can be distinguished by the characters listed in the diagnosis and their distinct DNA barcode sequences. Crawford described L. fedorense and L. swenki in separate papers in the same year (1906a, b) but did not comment on their similarity. Instead, he contrasted both with L. lusorium (as H. galpinsiae ). We agree that L. fedorense and L. swenki bear some resemblance to the Onagraceae specialist L. ( Sphecodogastra ), but a close relationship is not supported by phylogenetic studies, despite the intriguing results of Stevens (1920) summarised below.

Biology. Stevens (1920) reports L. swenki as being a regular visitor to flowers blooming in the late afternoon and evening. These include Mirabilis hirsuta (Pursh) MacMill. (Nyctaginaceae) , Dalea villosa (Nutt.) Spreng. (Fabaceae) (males), Linum rigidum Pursh (Linaceae) , and Hieracium umbellatum L. ( Asteraceae ). The greatest activity of L. swenki was an hour before sunset, although it was present at other times in the day ( Stevens 1920). Lasioglossum swenki has also been collected on Oenothera grandis (Britton) Smyth (Onagraceae) , Cleome serrulata Pursh (Capparaceae) , Mentzelia (Loasaceae) , and Helianthus petiolaris Nutt. (Asteraceae) . There are no published records of its nesting biology or social level, but it is believed to be a solitary, ground-nesting species. The species seems to have a preference for sandy areas like dunes (see Stevens 1920; Grundel et al. 2011).

DNA barcodes. Three individuals were sequenced (maximum intraspecific p-distance: 2.1%). Consensus sequences of L. fedorense (n=2) and L. swenki (n=2) collected in sympatry have 43 diagnostic substitutions (minimum intraspecific p-distance: 5.7%). Fixed substitutions at 16 sites distinguish L. swenki from L. fedorense and L. sopinci : 81(C), 168 (C), 192(T), 219(C), 225(C), 231(C), 234(T), 345(T), 354(A), 372(T), 381(A), 396(C), 450(T), 504(T), 531(C), and 633(C) (see Table 2). Three unique nucleotide substitutions among black weak-veined Lasioglossum were found: positions 168(C), 231(C), and 531(C).

Range. Fig. 42 .

Specimens examined. 431 (405 females, 40 males). Deposited in AMNH, ANSP, BBSL, CAS, CNC, CSCA, CUIC, EMEC, IRCW, MCZ, MSUC, PCYU, PMAE, SEMC, and UCRC. Localities with specimens with brown metasoma marked with asterisk .

CANADA. ALBERTA: Division 1: CFB Suffield NWA; Medicine Hat ; MANITOBA: Division 7: Aweme, E .

MEXICO: Chihuahua: Samalayuca; Samalayuca, 3 mi. S.

USA. INDIANA: Porter Co. : Indiana Dunes National Lakeshore *; MICHIGAN: Ottawa Co.: Grand Haven ;

MINNESOTA: Anoka Co. : Fridley, sand dunes; NEBRASKA: Cuming Co.: West Point; Garden Co.: Oshkosh, 8 mi NE; Thomas Co.: Thedford; NEW MEXICO: Otero Co.: Sacramento Mtns., High Rolls; Roosevelt Co.: Oasis S.P., nr. Portales; Portales, 5 mi. N; NORTH DAKOTA: Ransom Co.: Sheldon; OKLAHOMA: Woodward Co.: Woodward, 6 km NE; TEXAS: Ward Co.: Monahans; Monahans, Sand Hills S.P.; Winkler Co.: Rd. 404, 8 mi. E Hwy 18; UTAH: Cache Co.: Green Canyon; Emery Co.: Buckskin Spring; Flat Top Pass; Gilson Butte Well; Gilson Butte, 4 mi. N; Junction Goblin Valley. Rd. & Hwy. 24; Little Gilson Butte, 0.5 mi E; Little Gilson Butte, 2 mi. E; Little Gilson Butte, 3.2 mi E; San Rafael Des., 2 mi E Flat Top Pass; San Rafael Des., 3 mi. E Flat Top Pass; San Rafael Des., 3 mi SSE Temple Mt.; Temple Mt., Wash camp; Wild Horse Creek, N of Goblin Valley.; Wild Horse Creek, 1. 5 mi. NW Wild Horse Butte; Garfield Co.: Bullfrog Creeks, nr. Lk. Powell; San Juan Co.: Bluff, 5 mi. W, ‘Bluff’ dunes; WISCONSIN: Jackson Co.*; Monroe Co.*

SUBGENUS EVYLAEUS ROBERTSON 1902

Evylaeus Robertson 1902b: 247 .

Type species: Halictus arcuatus Robertson 1893 , by original designation (= H. cinctipes Provancher 1888 ).

Lasioglossum (Evylaeus) in our restricted sense includes a small number of North American species. Only the type species, L. cinctipes , occurs in the East. The remaining species confirmed for this subgenus, L. amicum ( Cockerell 1897b) , L. argemonis ( Cockerell 1897a) , L. giffardi ( Michener 1937) , and L. robustum ( Crawford 1907a) are known from the western United States. Lasioglossum nigricalle ( Vachal 1904) , known only from the male, also belongs to this subgenus, but this name may be a synonym of L. cinctipes . This species is only known from Colorado, although the locality label reads Nevada ( Moure & Hurd 1987; JG pers. obs.). Additional extralimital species may occur in this group, but additional study is required.

Subgeneric diagnosis

Female L. ( Evylaeus ) can be recognised by the following combination of characters. Integument black-brown; head much wider than long (L/W ratio = 0.83–0.93) ( Fig. 43A ); inner metatibial spur denticulate-serrate, teeth not exceeding width of rachis ( Fig. 5L ); mesepisternum rugulose to rugose; propodeum without lateral carina extending to dorsal surface, except in L. cinctipes , which has a coarsely rugose propodeum and metapostnotum giving the appearance of complete carina ( Fig. 79A ); and T1 without appressed hairs ( Fig. 80A ).

Lasioglossum (Evylaeus) females can be distinguished from the strong-veined Lasioglossum subgenera Lasioglossum s. s. and L. (Leuchalictus) by the state of vein 1r-sm ( Fig. 1A ). Lasioglossum (Sphecodogastra) and L. ( Hemihalictus ) in North America are both variable but can be distinguished from L. ( Evylaeus ) through a combination of characters. Most L. ( Sphecodogastra ) and L. ( Hemihalictus ) females in North America have the inner metatibial spur pectinate ( Fig. 5 ), or in some western species have large denticulations, unlike the small, indistinct teeth which occur in L. ( Evylaeus ). Many L. ( Sphecodogastra ) and L. ( Hemihalictus ) females can also be distinguished by the length of the head, which is most often longer than L. ( Evylaeus ) (L/W ratio = 0.89–1.11) ( Figs. 4 , 43 ). Some L. ( Hemihalictus ) females also have appressed hairs on T1 ( Fig. 82A ).

Male L. ( Evylaeus ) can be recognised by the following combination of characters. Integument black-brown; head short, clypeus not extending much below suborbital line ( Fig. 44A ); antennal flagellomeres more than 2X longer than wide; metasomal sterna with short pubescence (1–1.5 OD), without distinctive setal patterns or raised medial area on S6; retrorse lobe absent ( Fig. 46A ).

Lasioglossum (Evylaeus) males are easily distinguished from other North American subgenera of Lasioglossum by the absence of the retrorse lobe in combination with black integument, and absence of distinctive setal patterns on S6. All L. ( Sphecodogastra ) in North America have the retrorse lobe present ( Fig. 46 ), some extralimital species lack the retrorse lobe. Most L. ( Sphecodogastra ) have very sparse, short sternal hairs, appearing nearly absent (as in Fig. 85A ), except in the case of the Onagraceae specialists, which can be recognized by the longitudinal raised area on S6 (as in Fig. 85B ). Other Lasioglossum lacking a retrorse lobe in North America are either metallic, or in the case of L. (Leuchalictus), have distinct S6 setal patterns. The black integument distinguishes L. ( Evylaeus ) from all North American L. (Dialictus).

Figures

FIGURE 1. Forewings of female Lasioglossum with arrows indicating weak distal veins. (A) Individual with three submarginal cells. (B) Individual with two submarginal cells. Basal vein (b), pterostigma (pt). Numbers indicate submarginal cells. Modified from Gibbs (2010a).

FIGURE 4. Faces of female Lasioglossum subgenus Hemihalictus in frontal view. (A) L. birkmanni. (B) L. fedorense. (C) L. foxii. (D) L. inconditum. (E) L. lustrans. (F) L. macoupinense. (G) L. nelumbonis. (H) L. pectinatum. (I) L. pectorale. (J) L. sopinci. (K) L. swenki. Scale bar = 1 mm.

FIGURE 5. Drawings of inner metatibial spurs of female Lasioglossum subgenera Hemihalictus (A-K), Evylaeus (L), and Sphecodogastra (M-Q). (A) L. birkmanni. (B) L. fedorense. (C) L. foxii. (D) L. inconditum. (E) L. lustrans. (F) L. macoupinense. (G) L. nelumbonis. (H) L. pectinatum. (I) L. pectorale. (J) L. sopinci. (K) L. swenki. (L) L. cinctipes. (M) L. boreale. (N) L. comagenense. (O) L. quebecense. (P) L. seillean. (Q) L. truncatum. See McGinley (2003) figures 61, 62, and 65 for images of inner metatibial spurs of L. lusorium, L. oenotherae, and L. texanum.

FIGURE 6. Faces of male Lasioglossum subgenus Hemihalictus in frontal view. (A) L. birkmanni. (B) L. fedorense. (C) L. foxii. (D) L. inconditum. (E) L. lustrans. (F) L. macoupinense. (G) L. nelumbonis. (H) L. pectinatum. (I) L. pectorale. (J) L. sopinci. (K) L. swenki. Scale bar = 1 mm.

FIGURE 7. Genital capsule of male Lasioglossum subgenus Hemihalictus in dorsal view. (A) L. birkmanni. (B) L. fedorense. (C) L. foxii. (D) L. inconditum. (E) L. lustrans. (F) L. macoupinense. (G) L. nelumbonis. (H) L. pectinatum. (I) L. pectorale. (J) L. sopinci. (K) L. swenki. Scale bar = 1 mm.

FIGURE 8. Genital capsule of male Lasioglossum subgenus Hemihalictus in ventral view. (A) L. birkmanni. (B) L. fedorense. (C) L. foxii. (D) L. inconditum. (E) L. lustrans. (F) L. macoupinense. (G) L. nelumbonis. (H) L. pectinatum. (I) L. pectorale. (J) L. sopinci. (K) L. swenki. Scale bar = 1 mm.

FIGURE 16. Lateral habitus of male Lasioglossum (Hemihalictus) fedorense (Crawford). Scale bar = 1 mm.

FIGURE 37. Alternate colour patterns of the metasomal terga of (A) female Lasioglossum sopinci and (B) female Lasioglossum swenki.

FIGURE 38. Lateral habitus of male Lasioglossum (Hemihalictus) sopinci (Crawford). Scale bar = 1 mm.

FIGURE 40. Lateral habitus of female Lasioglossum (Hemihalictus) swenki (Crawford). Scale bar = 1 mm.

FIGURE 41. Lateral habitus of male Lasioglossum (Hemihalictus) swenki (Crawford). Scale bar = 1 mm.

FIGURE 42. Distribution map of Lasioglossum (Hemihalictus) swenki (Crawford). Heat map indicates predicted suitable range based on maximum entropy niche-modelling. Black circles indicate actual geo-referenced specimen records.

FIGURE 43. Faces of female Lasioglossum subgenera Evylaeus (A) and Sphecodogastra (B-I) in frontal view. (A) L. cinctipes. (B) L. boreale. (C) L. comagenense. (D) L. lusorium. (E) L. oenotherae. (F) L. quebecense. (G) L. seillean. (H) L. texanum (I) L. truncatum. Scale bar = 1 mm.

FIGURE 44. Faces of male Lasioglossum subgenus Evylaeus (A) and Sphecodogastra (B-I) in frontal view. (A) L. cinctipes. (B) L. boreale. (C) L. comagenense. (D) L. lusorium. (E) L. oenotherae. (F) L. quebecense. (G) L. seillean. (H) L. texanum (I) L. truncatum. Scale bar = 1 mm.

FIGURE 46. Genital capsules of male Lasioglossum subgenus Evylaeus (A) and Sphecodogastra (B-I) in ventral view. (A) L. cinctipes. (B) L. boreale. (C) L. comagenense. (D) L. lusorium. (E) L. oenotherae. (F) L. quebecense. (G) L. seillean. (H) L. texanum (I) L. truncatum. Scale bar = 1 mm.

FIGURE 77. Propodeum and metapostnotum of female Lasioglossum (Hemihalictus) of the fedorense species-group. (A) L. sopinci showing coarse sculpture. (B) L. fedorense showing fine sculpture. (C) L. swenki showing fine sculpture.

FIGURE 78. Mesepisternum of female Lasioglossum (Hemihalictus) of the fedorense species-group. (A) L. swenki showing finely punctate surface. (B) L. fedorense showing impunctate surface.

FIGURE 79. Propodeum and metapostnotum of female Lasioglossum (Evylaeus) and L. (Sphecodogastra). (A) L. cinctipes showing coarse, rugose sculpture. (B) L. truncatum showing coarse, rugose sculpture. (C) L. boreale showing fine sculpture and weak propodeal carinae. (D) L. comagenense showing fine sculpture and distinct propodeal carinae. (E) L. quebecense showing fine sculpture and distinct propodeal carinae. (F) L. seillean showing fine sculpture and distinct propodeal carinae.

FIGURE 80. Metasomal terga of female Lasioglossum. (A) L. cinctipes showing finely punctate apical impressed areas. (B) L. truncatum showing impunctate apical impressed areas.

FIGURE 82. Propodeum, metapostnotum and anterior surface of T1 of female Lasioglossum (Hemihalictus). (A) L. lustrans showing fine metapostnotal sculpture and subappressed hairs on T1. (B) L. foxii showing metapostnotal rugae not reaching posterior dorsal margin. (C) L. inconditum showing metapostnotal rugae reaching posterior dorsal margin.

FIGURE 85. Metasomal sterna of male Lasioglossum (Spheocodagastra) with arrows indicating pubescence and S6 medial area. (A) L. boreale showing short, sparse hairs and normal S6. (B) L. oenotherae showing long, dense hairs and concave S6.