Lasioglossum (Dialictus) izawsum Gibbs

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 120-124

Lasioglossum (Dialictus) izawsum Gibbs , new species

( Figures 134–138 )

Holotype. Ƥ USA, Massachusetts, Franklin Co., Montague WMA, N42.56767 W072.51897, 7–8.x.2008 (J. Milam); [ PCYU].

Diagnosis. Female L. izawsum can be recognised by the following diagnostic combination: labrum with flattened apical process, dorsal keel absent ( Fig. 6 B); pronotal ridge carinate; scopa absent; mandible with small preapical tooth; and gena subequal to eye in width. They are most similar to L. simplex , L. furunculum , L. sitocleptum and L. michiganense . Female L. furunculum , L. simplex , and L. sitocleptum lack a preapical tooth on the mandible. Lasioglossum simplex also lacks a carinate pronotal ridge. Female L. michiganense have gena wider than eye and mesepisternum vertically carinulate.

Male L. izawsum can be recognised by the following diagnostic combination: head and mesosoma green, lower paraocular area with moderately dense tomentum, postgena imbricate, pronotal ridge carinate, mesoscutum imbricate, and S7 median lobe acuminate. They are most similar to L. platyparium , L. michiganense and L. cephalotes . Male L. platyparium are bluish with polished postgena. Male L. michiganense have S7 median lobe clavate. Male L. cephalotes have a stronger pronotal collar and denser tomentum on the lower paraocular area.

Description. FEMALE. Length 4.17–4.54 mm; head length 1.24–1.27 mm; head width 1.46–1.48 mm; forewing length 3.15–3.27 mm.

Colouration. Head and mesosoma blue to bluish green. Clypeus with apical 1/2 blackish brown. Antenna dark brown, ventral surface reddish brown. Tegula reddish brown to brownish yellow. Wing subhyaline, venation and stigma dark yellowish brown. Legs brown, except tarsi reddish brown. Metasoma dark brown, terga and sterna with apical margins translucent brownish yellow.

Pubescence. Dull white. Sparse. Head and mesosoma with moderately dense woolly hairs (1–1.5 OD), longest on genal beard, metanotum, and mesopleuron (2–2.5 OD). Inner eye margin with subappressed hairs. Pronotal collar without dense tomentum. Propodeum with moderately sparse plumose hairs on lateral and posterior surfaces (1.5–2 OD).

Mesofemoral and mesotibial combs dense but short relative to non-parasitic species. Metafemoral scopa reduced relative to nest-building species, only a few elongate hairs curving above ventral surface. Penicillus greatly reduced, indistinguishable from other hairs. Metasomal terga with moderately sparse, fine hairs. T1 acarinarial fan with dorsal opening subequal to width of lateral hair patches. T2–T3 basolaterally and T4 entirely with very sparse tomentum. T2 apicolateral and T3–T4 apical margins with very sparse fringes. Sternal hairs erect, posteriorly directed (1.5–2.5 OD).

Surface sculpture. Face polished, punctation fine. Clypeus with punctation sparse (i=1.5–3d). Supraclypeal area with punctation moderately sparse (i=1–3d). Lower paraocular and antennocular areas with punctation moderately sparse (i=1–1.5d). Upper paraocular area and frons with punctation contiguous. Ocellocular area punctate (i=1–1.5d). Gena lineolate. Postgena imbricate. Mesoscutum weakly imbricate, more polished posteriorly, punctation fine, sparse between parapsidal lines (i=1–2.5d), denser laterad of parapsidal line (i≤d) and contiguous on anterolateral portion. Mesoscutellum similar to mesoscutum, submedial punctation sparse (i=1–3d). Axilla punctate. Metanotum imbricate. Preëpisternum rugulose. Hypoepimeral area ruguloso-imbricate. Mesepisternum dorsal half rugulose, ventral half imbricate. Metepisternum with dorsal 1/3 carinulate, ventral 2/3 imbricate. Metapostnotum nearly completely rugoso-carinulate, posterior margin imbricate. Propodeum with dorsolateral slope rugulose-imbricate, lateral surface imbricate, posterior surface imbricate-tessellate. Metasomal terga polished except apical impressed areas faintly coriarious, punctation dense basally (i=1–1.5d), apical half sparse (i=1.5–3d), T1 apical impressed area impunctate medially.

Structure. Head very wide (length/width ratio = 0.84–0.87). Eyes convergent below (UOD/LOD ratio = 1.17–1.21). Labrum enlarged and flattened with distinct basal tubercle, apical process without dorsal keel. Mandible slender, extending beyond opposing clypeal angle, preapical tooth small. Clypeus 1/3 below suborbital tangent, apicolateral margins strongly convergent. Antennal sockets distant (IAD/OAD> 1.4). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Gena subequal to eye. Pronotal dorsolateral angle slightly obtuse. Pronotal ridge carinate, not interrupted by oblique sulcus. Basitibial plate with apical carina weak. Inner metatibial spur pectinate with 3–4 short branches. Metapostnotum truncate (MMR ratio = 1.32–1.35), posterior margin narrowly rounded onto posterior surface. Propodeum with oblique carina very weak, lateral carina not reaching dorsal margin. T5 medial specialized area reduced in size relative to non-parasitic species.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length mm 4.05 mm; head length 1.32–1.43 mm; head width 1.42–1.49 mm; forewing length 3.15 mm.

Colouration. Flagellum ventral surface reddish brown. Legs brown, except tibial bases and apices, and tarsi yellow to brownish yellow.

Pubescence. Face below eye emargination with sparse tomentum, partially obscuring lower paraocular area, nearly absent from clypeus and supraclypeal area. S2–S5 lateral portions with moderately spare plumose hairs (1–1.5 OD).

Surface sculpture. Lower paraocular and supraclypeal areas moderately sparse (i=1–2d). Frons reticulate, punctation moderately sparse between parapsidal lines (i=1–2.5d), dense laterad of parapsidal line and on anterolateral portion (i≤d). Mesepisternum rugulose. Metapostnotum crescentic, completely rugoso-carinulate. Propodeum with dorsolateral slope rugose, posterior surface rugulose-imbricate. Metasomal terga distinctly punctate (i=1–2d), apical impressed margin impunctate.

Structure. Head wide (length/width ratio = 0.93–0.96). Eyes strongly convergent below (UOD/LOD ratio = 1.48– 1.56). Clypeus 2/3 below suborbital tangent, apicolateral margins convergent. Antennal sockets distant (IAD/OAD = 1.5). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Pedicel subequal to F1. F2 length 1.8X F1. F2–F10 moderately short (length/width ratio = 1.40–1.50). Pronotal ridge carinae. Metapostnotum relatively long (MMR ratio = 1.18), posterior margin narrowly rounded onto posterior surface.

Terminalia . S7 with median lobe acuminate, apex rounded ( Fig. 138 ). S8 with apicomedial margin weakly convex ( Fig. 138 ). Genital capsule as in Fig. 138 . Gonobase with ventral arms separated. Gonostylus small, dorsal setae elongate. Retrorse lobe moderately elongate, weakly attenuated apically.

Range. Massachusetts, Pennsylvania ( Fig. 139 ). USA: MA, PA.

Allotype. 3 USA: MASSACHUSETTS: Franklin Co., Montague WMA, powerline corridor, N42.56610 W072.53341, 5.x.2008 (Milam & King); [PCYU].

Paratypes. USA: MASSACHUSETTS: 1Ƥ Franklin Co., Montague WMA, gravel pit, N42.56767 W072.51879, 7– 8.x.2008 (J. Milam); 13 Franklin Co., Montague WMA, gravel pit, N42.55853 W072.52180, 5–6.x.2008 (J. Milam); [PCYU]; 1Ƥ Franklin Co., Montague WMA, Pt. 42, treated pitch-pine, N42.56321 W072.53181, 20–21.x.2009 (J. Milam); 1Ƥ Franklin Co., Montague WMA, Pt. 56, treated pitch-pine, N42.56212 W072.51859, 20–21.x.2009 (J. Milam); 1Ƥ Franklin Co., Montague WMA, Pt. 108, treated pitch-pine, N42. 56767 W072.51897, 2–5.x.2009 (J. Milam); 13 Franklin Co., Montague WMA, Pt. 119, treated pitch-pine, N42.55853 W072.52180, 8.ix.2010 (J. Milam); 3ƤƤ Franklin Co., Montague WMA, Pt. 119, treated pitch-pine, N42.55853 W072.52180, 5–6.x.2009 (J. Milam); 1Ƥ Franklin Co., Montague WMA, large gravel pit, N42.56957 W072.53617, 30.iv.2010 (D. King); [CUIC]; PENNSYLVANIA: 1Ƥ Westmoreland Co., Powdermill Nature Res., nr. Rector, 29.iv.1945 (C.J. McCoy); [UCMC].

Etymology. The specific epithet is treated as a noun in apposition.

DNA Barcode. Available. Multiple sequences.

Comments. Rare.

Lasioglossum izawsum is presumably a social parasite or cleptoparasite of nest-building Dialictus . The host is unknown but L. izawsum is almost exclusively known from sites where the new species L. katherineae (described below) has been found in abundance.

Figures

FIGURE 6. Labrum of female Dialictus; (A) nest-building species, (B) parasitic species. Arrows indicate apical process. (From Gibbs 2010 b).

FIGURE 134. Lasioglossum izawsum Gibbs female, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 135. Lasioglossum izawsum Gibbs female, dorsal view of mesosoma.

FIGURE 136. Lasioglossum izawsum Gibbs male, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 137. Lasioglossum izawsum Gibbs male, dorsal view of mesosoma.

FIGURE 138. Lasioglossum izawsum Gibbs, new species male terminalia, (A) ventral view, (B) dorsal view. Scale bar = 0.5 mm.

FIGURE 139. Distribution map of Lasioglossum izawsum (circles) and L. katherineae (stars).