Lasioglossum (Dialictus) furunculum Gibbs

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 98-99

Lasioglossum (Dialictus) furunculum Gibbs , new species

( Figures 108–109 )

Holotype. Ƥ USA, Massachusetts, Franklin Co., Montague WMA, Pt. 108, treated pitch-pine, N42. 56767 W072.51897, 5–6.x.2009 (J. Milam); [ PCYU].

Diagnosis. Female L. furunculum can be recognised by the following diagnostic combination: labrum with apical process flat, dorsal keel absent ( Fig. 6 B); mandible without preapical tooth; gena subequal to eye in width; and inner metatibial spur with four branches. They are most similar to L. izawsum and L. simplex . Female L. simplex lack a carinate pronotal ridge. Female L. izawsum has a distinct preapical tooth on the mandible and usually three branches on the inner metatibial spur.

Male unknown.

Description. FEMALE. Length 4.69 mm; head length 1.35 mm; head width 1.61 mm; forewing length 3.63 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 metabasitarsus yellowish brown, 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 (partially obscured). Face polished, punctation fine. Clypeus with punctation sparse (i=1.5–3d). Supraclypeal area with punctation moderately sparse (i=1–2.5d). 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), obscured apically.

Structure. Head very wide (length/width ratio = 0.84). Eyes convergent below (UOD/LOD ratio = 1.17). 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> 0.6). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Gena subequal to eye. Pronotal dorsolateral angle obtuse. Pronotal ridge carinate. Basitibial plate with apical carina weak. Inner metatibial spur pectinate with 4 short branches. Metapostnotum moderately elongate (MMR ratio = 1.18), 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. Unknown.

Range. Massachusetts ( Fig. 120 ).

DNA barcode. Unavailable.

Comments. Rare. Lasioglossum furunculum is presumed to be a social parasite or cleptoparasite of nest-building L. ( Dialictus ).

Due to the close similarity of L. furunculum and L. izawsum , their collection in the same study, and the partially obscured sculpture of the L. furunculum holotype, the former is described here with some trepidation. It is conceivable that L. furunculum is only an unusual specimen of L. izawsum , however, in addition to the tooth and spur characters, the inner surface of the metabasitarsus differs in colour between the two nominal taxa. The congruence between these three characters suggests that both species may be valid.

Figures

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

FIGURE 108. Lasioglossum furunculum Gibbs female, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 109. Lasioglossum furunculum Gibbs female, dorsal view of mesosoma.

FIGURE 120. Distribution map of Lasioglossum furunculum (star) and L. gotham (circles).