Lasioglossum (Hemihalictus) pectinatum ( Robertson 1890 )

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 : 49-52

Lasioglossum (Hemihalictus) pectinatum ( Robertson 1890)

( Figs. 4H , 5H , 6H , 7H , 8H , 30 , 31 , 76B )

Halictus pectinatus Robertson 1890, p. 315 (♀) Holotype. ♀ USA, Illinois, Macoupin Co., Carlinville (C. Robertson) [INHS]. Fixed by monotypy. Examined by JG 2011.

Evylaeus pectinatus (in Mitchell 1960: redescription, key ♀; Hurd 1979: catalogue; Moure & Hurd 1987: catalogue) Lasioglossum (Evylaeus) pectinatum (in Michener 1951: catalogue)

Diagnosis. Both sexes of L. pectinatum can be recognised by the combination of pronotum with carinate dorsolateral ridge, mesepisternum distinctly punctate ( Fig. 76B ), and mesoscutum polished due to lack of microsculpture. Neither sex has metapostnotal rugae reaching the posterior margin. Female L. pectinatum can be recognised by the unique inner metatibial spur, with approximately 15–20 short, narrow teeth, lengths not exceeding width of rachis ( Fig. 5H ). Female L. swenki are superficially similar but can be recognised by mesoscutum with imbricate microsculpture and inner metatibial spur with few, long teeth ( Fig. 5K )

Male L. pectinatum can be recognised by the combination of mandible elongate, extending to opposing clypeal base ( Fig. 6H ); gena wide, with sharp angle or tubercle at midlength ( Fig. 31 ); and clypeus with narrow, distal maculation ( Fig. 6H ). Males of L. fedorense , L. sopinci , and L. swenki also have long mandibles, but all three have a clypeal maculation extending the full length of the clypeus ( Figs. 6B, 6J, 6K ).

Redescription. FEMALE. Length 7.1–7.3 mm. Head length 1.97–2.08 mm. Head width 1.92–2.00 mm. Wing length 5.5–6.6 mm. (n=4)

Colour. Head and mesosoma black. Antenna black, except ventral surface of flagellum reddish brown. Tegula dark reddish brown. Legs dark brown, except medio- and distitarsi reddish brown. Wing membrane hyaline. Pterostigma reddish brown. Metasomal terga black-brown, apical margins reddish brown.

Structure. Head long (L/W ratio = 1.02–1.04). Clypeus 2/3–3/4 below suborbital line. Eyes convergent below (UOD:LOD = 1.02–1.09). Gena narrower than eye. Ocelli normal. Pronotal ridge sharply angled. Protibial spur with apical serrations longer or subequal to length of malus. Inner metatibial spur pectinate, teeth 15–20, basal teeth subequal to width of rachis. Propodeal lateral carina not reaching dorsal margin, oblique carina absent.

Surface sculpture. Supraclypeal area polished, punctures sparse. Gena and postgena polished. Mesoscutum polished, punctures distinctly separated throughout. Mesepisternum smooth, polished, distinctly punctate. Metapostnotum carinate-rugose basally, apical margin weakly imbricate. Propodeum imbricate-tessellate, dorsolateral slope smooth, punctate. Metasomal terga polished, apical impressed areas weakly coriarious; punctures deeps, dense throughout, narrowly impunctate on apical margin.

Pubescence. Head and mesosoma with sparse plumose hairs. Metafemoral scopa with dense plumose hairs. Metasomal terga without apical fimbriae. T1 with sparse, erect plumose hairs. Metasomal sterna with densely plumose scopa.

MALE. Length 5.3–6.0 mm. Head length 1.68–1.92 mm. Head width 1.65–1.9 mm. Wing length 4.5–4.7 mm. (n=2)

Colour. Head and mesosoma black. Clypeus yellow distally. Mandible yellow. Labrum yellow. Antenna black, except ventral surface of flagellum reddish brown. Legs dark brown, except tarsi and inner surface of protibia reddish brown. Wing membrane hyaline. Pterostigma reddish brown. Metasomal terga dark brown.

Structure. Head relatively long (L/W ratio = 0.97–1.02). Mandible long, reaching opposing mandibular base. Flagellomeres, except F1, moderately elongate, F2 longer than F1 and pedicel combined, much shorter than scape. Eyes weakly convergent below (UOD:LOD = 1.02–1.11). Gena much wider than eye, tuberculate at midlength. Pronotal ridge sharply angled. Propodeal lateral carina not reaching dorsal margin.

Surface sculpture. Supraclypeal area polished, punctures sparse. Gena and postgena polished. Mesoscutum polished, punctures clearly separated throughout. Mesepisternum polished, distinctly punctate. Metapostnotum polished-weakly imbricate, with short carinulae basally. Propodeum imbricate, posterior surface polished. Metasomal terga polished; punctures deep, close basally. T2–T6 apical impressed areas impunctate.

Pubescence. Head and mesosoma with sparse plumose hairs. Paraocular area below eye emargination with relatively sparse tomentum. Propodeum largely bare, with scattered plumose hairs. Metasomal terga nearly bare, apical fimbriae absent. Metasomal sterna with relatively long (1.5–2.5 OD), plumose hairs, except S5–S6 relatively bare.

Terminalia . As shown in Fig. 7H , 8H . Retrorse lobe long, narrow. Gonostylus round, with short setae.

Taxonomic notes. Lasioglossum pectinatum is a comparatively distinctive species, unlike any other Lasioglossum in the USA or Canada. The Neotropical species L. denticeps Michener (1954) and L. sertum ( Vachal 1904) , however, seem to have close affinities to L. pectinatum based upon morphological examination of the type series of these two species. There may also be additional undescribed species in this group occurring in the Neotropics.

The male of L. pectinatum is recognised here for the first time. Mitchell (1960) suggested that Evylaeus bradleyi might be the male of L. pectinatum (as E. pectinatus ), but this is incorrect (see L. sopinci below).

Biology. Lasioglossum pectinatum has a preference for Physalis spp. (Solanaceae) , upon which it has been collected and observed most frequently (JG pers. obs.; T. Roulston pers. comm.). Robertson (1928) recorded L. pectinatum from Physalis virginiana Mill. The only specimen other than the type examined by Mitchell (1960) was collected on Physalis heterophylla Nees. Floral specialization would partially explain why L. pectinatum is so poorly represented in collections. Robertson (1928) reports visitations to other plants including Circaea lutetiana L. ( Onagraceae ), Cryptotaenia canadensis L. ( Apiaceae ), and Helianthus tuberosus L. ( Asteraceae ), but visitations for pollen or nectar were not differentiated. The holotype was collected on Helianthus according to Robertson (1928). Lasioglossum pectinatum also visits Citrullus (Cucurbitaceae) ( Winfree et al. 2008).

The macrocephalic male is suggestive of intra-sexual conflict ( Kukuk & Schwarz 1988; Danforth 1991; Houston & Maynard 2012). There are no published records of its nesting biology or social level. It is presumably a solitary ground-nester, based on its phylogenetic affinities and floral host restrictions.

Range. Fig. 32 .

Material examined. 25 (21 females, 4 males). Deposited in CAS, CNC, CUIC, INHS, PCYU, PMNH, and RWRC. Locality marked with an asterisk represents a digital photograph of a male specimen submitted to www.BugGuide.net .

USA. ILLINOIS: Champaign Co.: Champaign; Hancock Co.: Mississippi River Sand Hills Nature Preserve ; Macoupin Co. : Carlinville ; MASSACHUSETTS: Middlesex Co.: Stow *; MISSOURI: Boone Co.: Columbia; Montgomery Co.: Graham Cave S.P.; St. Louis Co. : Beaumont Res., E of Eureka ; NEW JERSEY: Hunterdon Co.: Peaceful Valley ; NEW YORK: Seneca Co. : Trumansburg, 2 km NNE; OHIO: Crawford Co.: Benton ; PENNSYLVANIA: Bucks Co.: Traugers; Lancaster Co. : Pequea ; VIRGINIA: Clarke Co.: Blandy Experimental Farm ; WEST VIRGINIA: Hampshire Co.

DNA barcodes. A single male specimen has been DNA barcoded. A minimum p-distance of 9.3% separates L. pectinatum DNA barcodes from the most similar species included herein. Two nucleotide positions distinguish L. pectinatum from all other black, weak-veined Lasioglossum in the eastern USA: 15(A) and 507(C) (see Table 2).

Figures

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 30. Lateral habitus of female Lasioglossum (Hemihalictus) pectinatum (Robertson). Scale bar = 1 mm.

FIGURE 31. Lateral habitus of male Lasioglossum (Hemihalictus) pectinatum (Robertson). Scale bar = 1 mm.

FIGURE 32. Distribution map of Lasioglossum (Hemihalictus) pectinatum (Robertson). Heat map indicates predicted suitable range based on maximum entropy niche-modelling. Black circles indicate actual geo-referenced specimen records.

FIGURE 76. Mesepisternum of female Lasioglossum. (A) L. inconditum showing weak, rugulose sculpture. (B) L. pectinatum showing punctation. (C) L. pectorale showing coarse, rugose sculpture throughout. (D) L. comagenense showing weak, rugulose sculpture. (E) L. lusorium showing appressed pubescense. (F) L. truncatum showing rugose sculpture becoming rugulose anterior to mesocoxa.