Lasioglossum (Dialictus) anomalum (Robertson)

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 66-69

Lasioglossum (Dialictus) anomalum (Robertson)

( Figures 71A–D , 72A–E )

Halictus anomalus Robertson, 1892: 272 . ♀. Lectotype. ♀ USA, Illinois, Carlinville , 19.v. (C. Robertson); [INHS: 179,603] by W.E. LaBerge. Examined.

Taxonomy. Robertson, 1902: Dialictus anomalus ♂, p. 48 (description); Michener, 1951: Lasioglossum (Dialictus) anomalum , p. 1119 (catalogue); Mitchell, 1960: Dialictus anomalus ♂, p. 379 (redescription); Krombein, 1967: Lasioglossum (Dialictus) anomalum , p. 462 (catalogue); Hurd, 1979: Dialictus anomalus , p. 1964 (catalogue); Moure & Hurd, 1987: Dialictus anomalus , p. 89 (catalogue).

Diagnosis. Lasioglossum anomalum and L. occidentale can be recognised by the absence of vein 1rs-m resulting in only two submarginal cells ( Fig. 2B ). Some individuals of L. asteris also share this trait but are easily distinguished by their parasitic characters (see L. asteris below). Lasioglossum anomalum has a green head and mesosoma, a short face (length/width ratio = 0.95–1.00), faintly dusky wings and the apical half of T2–T3 nearly impunctate. Lasioglossum occidentale has a blue head and mesosoma, a longer face (length/ width ratio = 1.00–1.05), pale, hyaline wings and, at most, the apical impressed margin of T2–T3 impunctate.

Redescription. FEMALE. Length 4.15–4.64 mm; head length 1.22–1.27 mm; head width 1.27–1.34 mm; forewing length 3.05–3.23 mm.

Colouration. Head and mesosoma green with bluish reflections. Clypeus with apical half blackish brown, basal half, and supraclypeal area brassy. Antenna dark brown, flagellum with ventral surface light brown, F8– F10 with ventral surface orange. Mesoscutum with brassy reflections. Tegula reddish amber. Wing membrane subhyaline, venation and pterostigma brownish amber. Metasoma dark brown, terga and sterna with apical margins reddish to translucent yellowish brown.

Pubescence. Dull white. Sparse. Head and mesosoma with sparse woolly hairs (1 OD), longest on genal beard, metanotum and mesopleuron (1.5–2.5 OD). Lower paraocular area without tomentum. Propodeum with sparse plumose hairs on lateral and posterior surfaces (1–2 OD). Metasomal terga with sparse, fine setae. T1 acarinarial fan small, widely spaced appressed hairs, not at all encircling the central area. Metasomal terga without appressed tomentum.

Surface sculpture. Face imbricate, punctation strong. Clypeus polished, basal margin imbricate, punctation moderately sparse (i=1–3d). Supraclypeal area with punctation sparse (i=1–2.5d). Lower paraocular area punctation dense (i≤d). Antennocular area punctation moderately sparse (i=1–2d). Upper paraocular area and frons reticulate-punctate. Ocellocular area punctate (i≤d). Gena and postgena imbricate. Mesoscutum imbricate, punctation moderately coarse, moderately sparse between parapsidal lines (i=1–1.5d), close laterad of parapsidal lines (i≤d), contiguous on anterolateral portion. Mesoscutellum polished, punctation similar to mesoscutum, submedial punctation sparse (i=2–5d). Axilla punctate. Metanotum imbricate. Preëpisternum and mesepisternum strongly imbricate/weakly rugulose between close punctures (i<d). Metepisternum with dorsal half ruguloso-striate, ventral half imbricate. Metapostnotum incompletely striate, posterior margin imbricate. Propodeum with dorsolateral slope ruguloso-imbricate, lateral and posterior surfaces tessellate. Metasomal terga polished except apical impressed areas distinctly coriarious, punctation on basal halves very sparse (i=3–6d), apical half impunctate (except along premarginal line).

Structure. Head wide (length/width ratio = 0.95–0.96). Eyes convergent below (UOD/LOD ratio = 1.25– 1.31). Clypeus ½ below suborbital tangent, apicolateral margins convergent. Antennal sockets close (IAD/ OAD <0.5). Frontal line carinate, ending 2 OD below median ocellus. Gena narrower than eye. Vein 1rs-m absent. Inner metatibial spur pectinate with 3–4 teeth. Metapostnotum moderately elongate (MMR ratio = 1.26–1.35), posterior margin weakly angled onto posterior surface. Propodeum with oblique carina fine but distinct, lateral carina nearly reaching dorsal margin.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 4.15– 5.31 mm; head length 1.15–1.34 mm; head width 1.20–1.34 mm; forewing length 2.99–3.42 mm.

Colouration. Flagellum with ventral surface brown. Tarsi reddish brown.

Pubescence. Face not obscured by tomentum. S2–S3 with sparse, erect hairs (1–1.5 OD). S4–S5 apicolateral portions with more dense erect hairs (1–1.5 OD).

Surface sculpture. Hypoepimeral area and mesepisternum punctation more distinct and coarser (i≤d).

Structure. Head wide to round (length/width ratio = 0.96–1.00). Eyes strongly convergent below (UOD/ LOD ratio = 1.52–1.57). Antennal sockets distant (IAD/OAD> 1.1). Frontal line carinate, ending 2.5 OD below median ocellus. Pedicel longer than F1. F2 length 1.2–1.4X F1. F2–F10 short (length/width ratio = 1.09–1.25). Metapostnotum truncate (MMR ratio = 1.35–1.38), posterior margin weakly angled onto posterior surface.

Terminalia . S7 with median lobe narrowly clavate, apex rounded. S8 with apicomedial margin strongly convex. Genitalia as in Fig. 72D–E . Gonobase with ventral arms narrowly separated. Gonostylus small, dorsal setae elongate. Retrorse lobes short and broad.

Range. Ontario west to Minnesota, south to Colorado, Indiana and Iowa ( Fig. 70 ).

Additional material examined. CANADA: ONTARIO: 3♀ 1♂ Haldimand-Norfolk Co., Nixon West , N42°13´W080°26´, 22.vii.1995 (L. Packer); [ PCYU] ; 1♀ Iona , 25.v.1962, on Salix, (G. Knerer) ; 1♀ Iona , 1.ix.1963 on Solidago, (G. Knerer) ; [ ROM] ; 1♀ 1♂, Iona , 15.ix.1963 (G. Knerer) ; 1♀ York University, Keele Campus, nr Pond Rd. , 4.viii.2006 (E. Willis); [ PCYU] ; USA: COLORADO: 1♀ Larimer Co., N40.6833 W105.3975, 11–12.v.2004 (S.W. Droege); [ PCYU] ; ILLINOIS: 7♀ Cook Co., Chicago , N41.8098 W087.6457, 14.v.2009 (S.W. Droege) ; INDIANA: 1♀ Jasper Co., prairie border, 16.vii.2003, 13:15, ( R. P. Jean) ; 1♀ Jasper Co., Nipsco , wpt, 1.vii.2003, 7:00–16:10, ( R. P. Jean) ; IOWA: 1♀ Hamilton Co., Chicago Cen. & Pacific RR, 340 m, 5 km W of Webster City, N42°28´17´´ W093°55´04´´, 18.v.2003, bpt, (C. Hemsley) ; MICHIGAN: 1♀ N42.8276 W084.22097, 27.vi.2006 (J. Gibbs) ; MINNESOTA: 1♀ Minnetonka, Univ. of Minnesota Arboretum , vi.2005 (L. Packer) ; NEBRASKA: 1♀ Douglas Co., N41.2774 W095.9116, 10.v.2007 (S.W. Droege); [ PCYU] ; WISCONSIN: 3♀ Dane Co., Raymond Rd. , 3.vii.1996; [ IRCW] ; 1♀ Sauk Co., N43.3376 W89.9494, 5.ix.2007 (M. Mossman); [ PCYU] .

Floral Records. ASTERACEAE : Rudbeckia , Solidago , Symphyotrichum pilosum , BERBERIDACEAE : Jeffersonia diphylla , BRASSICACEAE : Barbarea , Capsella bursa-pastoris , HYDROPHYLLACEAE : Phacelia , LAMIACEAE : Monarda fistulosa var. menthaefolia , LILIACEAE : Hypoxis hirsuta , RHAMNA- CEAE: Ceanothus , RUBIACEAE : Houstonia purpurea , SALICACEAE : Salix , SAXIFRAGACEAE : Saxifraga pennsylvanica , SCROPHULARIACEAE : Besseya plantaginea , Penstemon .

Comments. Uncommon. This is the type species for the genus-group name Dialictus . A single specimen of L. anomalum from Guelph, Ontario with vein 1rs-m present in both wings has been examined (J. Gibbs in prep.). Specimens of this form will key out to L. tenax but can be distinguished from that species by the contiguous mesepisternal punctures and lack of tomentum on the metasomal terga. Males with vein 1rs-m present would key out to L. zophops but can be distinguished from that species by the short flagellomeres (length/ width ratio = 1.09–1.25).

Figures

FIGURE 2. Forewings of female Lasioglossum subgenus Dialictus. (A) Typical forewing with three submarginal cells. Pterostigma (pt), basal vein (b), arrows indicate weakened veins. (B) Forewing with two submarginal cells. Arrows indicate weakened veins.

FIGURE 70. Distribution of Lasioglossum albohirtum (dark grey) and L. anomalum (light grey).

FIGURE 71. Lasioglossum anomalum (Robertson). Female (A) lateral habitus; (B) dorsal habitus; (C) face; (D) metasomal terga. Scale bars, A–C = 1 mm.

FIGURE 72. Lasioglossum anomalum (Robertson). Male (A) lateral habitus; (B) dorsal habitus; (C) face; (D) ventral view of genital capsule; (E) dorsal view of genital capsule. Scale bars, A–C = 1 mm, E = 0.5 mm.