Lasioglossum (Dialictus) imbrex Gibbs, 2010

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 153-156

Lasioglossum (Dialictus) imbrex Gibbs , new species

( Figure 123A–D )

Holotype. ♀ CANADA, British Columbia, Okanagan-Similkameen Reg. Dist., Osoyoos, Mt. Kruger , Strawberry Crk. Rd. , N-site, N49.0421 W119.5114, 505 m, 16.vii.2008 (L. R. Best); [ PCYU: LRB-2325].

Diagnosis. Females of L. imbrex , L. ellisiae and L. tegulare may be easily distinguished from other Canadian Dialictus by their large, distinctly punctate tegula with an acute posterior angle ( Fig. 7A ). Females of L. ellisiae and L. imbrex both have the mesepisternum smooth between punctures, with at most weak lines on the interspaces. Female L. imbrex have denser tomentum on the basal portions of T2–T3 and across the disc of T4 ( Fig. 123D ) than does L. ellisiae . Female L. tegulare have the mesepisternum between punctures dull due to strong microsculpture.

Male unknown.

Description. FEMALE. Length 4.51–5.12 mm; head length 1.24–1.31 mm; head width 1.26–1.38 mm; forewing length. 3.05–3.17 mm.

Colouration. Head and mesosoma dull metallic pale green with some golden and bluish reflections. Labrum sometimes reddish brown. Mandible orange. Clypeus with apical blackish brown and basal half, and supraclypeal area brassy. Antenna dark brown, with ventral surface brownish yellow. Tegula brown to black, central area reddish. Wing membrane subhyaline, venation and pterostigma pale yellowish brown. Legs dark brown, promedio- and prodistitarsi reddish, meso- and metadistitarsi reddish brown. Propodeum sometimes bluish. Metasoma dark brown, terga and sterna with apical margins reddish to translucent brownish yellow.

Pubescence. Dull white. Moderately dense. Head and mesosoma with moderately dense woolly hairs (1– 1.5 OD), longest on genal beard, metanotum and mesopleuron (2–2.5 OD). Lower paraocular and gena with moderately dense tomentum, partially obscuring surface. Propodeum with moderately dense plumose hairs on lateral and posterior surfaces (2–2.5 OD). Metasoma terga with moderately sparse, fine setae. T1 acarinarial fan complete. T3–T5 ventrolateral reflexed areas with few, erect hairs (2.5–3 OD). T2 basolaterally, T3 basally and laterally, and T4 entirely with moderately dense tomentum, partially obscuring surface. T2 apicolateral and T3–T4 apical margins with sparse fringes.

Surface sculpture. Face weakly imbricate, punctation moderately strong. Clypeus polished basal margin imbricate, punctation moderately dense (i=1–2d). Supraclypeal area with punctation moderately sparse (i=1– 2.5d). Lower paraocular area punctation dense (i<d). Antennocular area moderately dense (i=1–1.5d). Upper paraocular area, frons and ocellocular area reticulate-punctate. Gena and postgena lineolate. Mesoscutum tessellate, punctation fine, moderately dense between parapsidal lines (i=1–1.5d), dense on remainder of disc and along median line (i<d). Mesoscutellum polished, submedial punctation moderately dense (i=1–2d). Axilla reticulate-punctate. Metanotum imbricate. Preëpisternum rugulose. Hypoepimeral area reticulate-punctate. Mesepisternum polished to weakly imbricate, strongly punctate (i=1–1.5d). Metepisternum with dorsal quarter striate, ventral portion imbricate. Tegula distinctly punctate (i=1–2d). Metapostnotum incompletely rugoso-striate, posterior margin imbricate. Propodeum with dorsolateral slope rugulose, lateral surface ruguloso-tessellate, posterior surface tessellate. Metasomal terga polished except T1 declivitous surface and apical impressed areas weakly coriarious, punctation fine, on basal halves moderately dense (i=1–1.5d), moderately sparse, obscure on apical halves (i=1.5–2.5d).

Structure. Head wide (length/width ratio = 0.95–0.98). Eyes convergent below (UOD/LOD ratio = 1.14– 1.19). Clypeus 1/2–2/3 below suborbital tangent, apicolateral margins convergent. Antennal sockets close (IAD/OAD <0.5). Frontal line carinate, ending 2.5 OD below median ocellus. Gena narrower than eye. Tegula elongate with posterior margin angled posteromedially. Inner metatibial spur pectinate with 2–3 teeth. Metapostnotum moderately elongate (MMR ratio = 1.16–1.32), posterior margin weakly angled onto posterior surface. Propodeum with oblique carina weak, lateral carina weak not reaching dorsal margin.

MALE. Unknown.

Range. Alberta, British Columbia south to southern California ( Fig. 124 ).

Paratypes. CANADA: ALBERTA: 2♀ Writing-On-Stone P.P, 14.iv.1984 (A. T. Finnamore) ; 1♀ Writing-On-Stone P.P., 14.vi.1984 ( T. Spanton) ; 1♀ Writing-On-Stone P.P, 17–26.iv.1990, sage-north, (D. McCorquodale); 1♀ Writing-On-Stone P.P, 26.v–6.vi.1990, grass-south, (D. McCorquodale); 2♀ Writing- On-Stone P.P, 12–20.vi.1990, sedge-south, (D. McCorquodale); 1♀ Writing-On-Stone P.P, 1.viii.1990, (M. Klassen); [ PMAE] ; USA: CALIFORNIA : 1♀ Los Angeles Co., N34.1116 W118.7773, 30.v.2008 (S.W. Droege) ; 1♀ Mariposa Co., Forest Rd. , 1.1 mi S Eagle Pk., 11S N4173170 E 253922, 576 m, 24.v.2005 (L. Fuerst, J. Gibbs & E. Stephens) ; 1♀ Tueeulala Falls , 11S N4173170 E253922, 1225 m, 26.vii.2005 (E. Stephens) ; 1♀ Tueeulala Falls , 11S N4173170 E253922, 1225 m, 26.vii.2005 (H. Briggs & E. Stephens); [ BBSL] ; 1♀ Santa Monica Mtns. , N34.0464 W118.8976, 1.vi.2008 (S.W. Droege) ; 1♀ Santa Monica Mtns. , N34.1419 W118.7767, 30.v.2008 (S.W. Droege); [ PCYU] ; 1♀ Tuolumne Co., Poopenaut Vly., 1.2 mi SWbyS Dam , 11S N4202202 E253883, 1060 m, 30.vi.2005 (L. Fuerst); OREGON : 1♀ Farewell Bend S.P., N44.30962 W117.22057, 659 m, 27.vi.2007 (Gibbs & Sheffield); [ PCYU] .

Etymology. The specific epithet refers to a type of roof tile used in conjunction with another tile called a tegula in Ancient Greek and Roman architecture.

Floral records. ASCLEPIADACEAE : Asclepias , ASTERACEAE : Achillea millefolium .

Comments. Uncommon in Canada. This species belongs to the L. tegulare species-group. Specimens of the L. tegulare group in the western USA have most often been identified as L. tegulariforme (Crawford) , originally described from Nevada. The holotype of L. tegulariforme has an unusually long and acute posterior projection on the tegula that distinguishes it from other species in the L. tegulare group. DNA barcodes from L. tegulariforme individuals collected in Nevada are clearly different from DNA barcodes of L. imbrex . It is likely that the name L. tegulariforme has been too widely applied and many Western specimens actually belong to L. imbrex .

Figures

FIGURE 7. Tegula of (A) L. imbrex (tegulare species group), (B) L. oceanicum.

FIGURE 123. Lasioglossum imbrex new species. Female (A) lateral habitus; (B) dorsal habitus; (C) face; (D) metasomal terga. Scale bars, A–C = 1 mm.

FIGURE 124. Distribution of Lasioglossum imbrex (dark grey) and L. imitatum (light grey).