Lasioglossum (Dialictus) wheeleri (Mitchell)

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 208-211

Lasioglossum (Dialictus) wheeleri (Mitchell)

( Figures 224–226 )

Dialictus wheeleri Mitchell, 1960: 445 . 3.

Holotype. Ƥ USA, Massachusetts, Forest Hills, 29–30.viii.1922 [ NCSU]. Examined. Taxonomy. Krombein, 1967: Lasioglossum (Dialictus) wheeleri , p. 467 (catalogue); Moure and Hurd, 1987: Dialictus wheeleri , p. 140 (catalogue).

Diagnosis. Male L. wheeleri can be recognised by the following diagnostic combination: head round (length/width ratio = 0.98) ( Fig. 224 B), pronotal angle orthogonal (225), mesepisternal punctures distinct, and S7 apical lobe clavate with truncate apex. They are most similar to L. heterognathum , which has the pronotal angle obtuse. Female unknown.

Redescription. FEMALE. Length 4.72 mm; head length 1.51 mm; head width 1.54 mm; forewing length 3.87 mm

Colouration. Head and mesosoma purplish blue. Antenna dark brown, flagellum with ventral surface brownish yellow. Tegula dark amber. Wing membrane faintly dusky, venation and stigma brown. Legs brown, except tarsi dull brownish yellow. Metasoma brown, terga and sterna with apical margins translucent brownish yellow.

Pubescence. Dull white. Sparse throughout. Head and mesosoma with moderately sparse woolly hairs (1–1.5 OD), longest on genal beard, metanotum, and mesopleuron (2–2.5 OD). Clypeus and supraclypeal area with scattered squamose hairs, not obscuring surface. Paraocular area below eye emargination with subappressed tomentum, obscuring lower paraocular area. Propodeum with moderately dense plumose hairs on lateral and posterior surfaces (1–2 OD). Metasomal terga with sparse, fine hairs but no tomentum. S2–S5 with sparse erect hairs (1–2 OD).

Surface sculpture. Face polished, weakly imbricate, punctation fine. Clypeus an supraclypeal area punctation moderately dense (i=1–1.5d). Lower paraocular and antennocular areas with punctation dense (i≤d). Upper paraocular area and frons punctate-reticulate. Ocellocular area punctate (i=1–1.5). Gena weakly lineolate. Postgena weakly imbricate. Mesoscutum polished, punctation sparse between parapsidal lines (i=1–2d), relatively dense laterad of parapsidal line (i=1–1.5d) and dense on anterolateral portion (i≤d). Mesoscutellum polished, submedial punctation sparse (i=1–3d). Axilla punctate. Metanotum rugose. Preëpisternum rugose. Hypoepimeral area imbricate-punctate. Mesepisternum polished, punctate (i=1–2d). Metepisternum dorsal 2/3 rugoso-carinulate, ventral portion imbricate. Metapostnotum rugosocarinulate, rugae reaching posterior margin. Propodeum with dorsolateral slope rugose, lateral and posterior surfaces polished. Metasomal terga polished except apical impressed areas faintly coriarious, punctation fine (i=1–1.5d), apical impressed areas impunctate.

Structure. Head round (length/width ratio = 0.98). Eyes strongly convergent below (UOD/LOD ratio = 1.40). Labrum short, wide without apical process. Mandible reaching opposing clypeal angle, preapical tooth absent. Clypeus 1/ 2 below suborbital tangent, apicolateral margins weakly convergent. Antennal sockets distant (IAD/OAD> 1.5). Frontal line carinate, ending 2 OD below median ocellus. IOD greater than OOD. Pedicel shorter than F1. F2 length 1.8X F1. F2–F10 moderately elongate (length/width ratio = 1.67–1.77). Gena narrower than eye. Hypostomal carinae subparallel. Pronotal dorsolateral angle orthogonal. Pronotal ridge carinate, weakly interrupted by sulcus. Metapostnotum truncate (MMR ratio = 1.29), posterior margin narrowly rounded onto posterior surface. Propodeum with lateral carina short, not reaching dorsal margin.

Terminalia . S7 with median lobe clavate, apex truncate, flat ( Fig. 226 ). S8 with apicomedial margin weakly convex ( Fig. 226 ). Genital capsule as in Fig. 226 . Gonobase with ventral arms narrowly separated. Gonostylus small, dorsal setae elongate. Retrorse lobe narrow, weakly attenuated apically.

Range. Massachusetts, topotypical ( Fig. 223 ). DNA Barcode. Unavailable.

Comments. Rare (only known from the holotype).

Lasioglossum wheeleri may be a socially parasitic species. The combination of a wide head and carinate pronotal ridge is typical of parasitic Lasioglossum . If L. wheeleri is a parasite, then L. ascheri and L. curculum , described above, are candidates for the female of this species.

Figures

FIGURE 223. Distribution map of Lasioglossum trigeminum (circles) and L. wheeleri (star).

FIGURE 224. Lasioglossum wheeleri (Mitchell) male, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 225. Lasioglossum wheeleri (Mitchell) male, dorsal view of mesosoma.

FIGURE 226. Lasioglossum wheeleri (Mitchell) male terminalia, ventral view. Scale bar = 0.5 mm.