Lasioglossum (Dialictus) curculum Gibbs

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 80-83

Lasioglossum (Dialictus) curculum Gibbs , new species

( Figures 90–91 )

Holotype. Ƥ USA, Maryland, Laurel, 20.v.1965 (W.R.M. Mason); [ CNC].

Diagnosis. Female L. curculum can be recognised by the following diagnostic combination: labrum wide, flat, dorsal keel absent ( Fig. 6 B); mandible with distinct preapical tooth; gena much wider than eye; mesepisternum punctate; metapostnotum rugoso-carinulate; tibial scopa reduced; and inner metatibial spur with short branches only slightly longer than width of rachis. Lasioglossum ascheri is most similar but lacks a preapical tooth on the mandible and has long branches on the inner metatibial spur, clearly wider than the rachis. They are similar to L. michiganense , which has the mesepisternum vertically carinulate.

Male unknown.

Description. FEMALE. Length mm 5.14; head length 1.51 mm; head width 1.82 mm; forewing length 4.05 mm.

Colouration. Head and mesosoma purplish with blue reflections. Clypeus apical portion blackish brown. Antenna dark brown, flagellum with ventral surface orange-yellow. Tegula reddish brown. Wing membrane subhyaline, venation and pterostigma reddish brown. Legs brown, except tarsi brownish yellow. Metasoma reddish brown, terga and sterna margins translucent reddish to yellowish brown.

Pubescence. Dull white. Sparse. Head and mesosoma with moderately dense woolly hairs (1–1.5 OD), longest on genal beard, metanotum, and mesopleuron (1.5–2 OD). Face without appressed hairs. Clypeus distal margin with long bristles (2–3 OD). Propodeum with moderately dense plumose hairs on lateral and posterior surfaces (1.5–2 OD). Mesofemoral and mesotibial combs present but sparse relative to non-parasites. Femoral scopa greatly reduced, only a few long, curved hairs remain. Penicillus reduced relative to non-parasites. Metasomal terga with sparse, fine hairs and no tomentum. T1 acarinarial fan with wide dorsal opening. T2–T3 apicolateral and T4 apical margins with very sparse fringes. Metasomal sterna with sparse posteriorly curved hairs (2–3 OD).

Surface sculpture. Face polished, punctation fine. Clypeus with punctation sparse (i=1–4d). Supraclypeal area punctation fine, sparse (i=1–2.5d). Lower paraocular area punctation dense (i=1–2d). Antennocular area punctation moderately dense (i=1–1.5d). Upper paraocular area and frons reticulate-punctate. Ocellocular area punctate (i=1–1.5d). Gena lineolate. Postgena imbricate. Mesoscutum polished, weakly imbricate medially. Mesoscutal punctation fine moderately sparse between parapsidal lines (i=1–3d), dense laterad of parapsidal line (i=1–1.5d), contiguous on anterolateral portion. Mesoscutellum similar to mesoscutum, submedial punctation sparse (i=3–6d). Axilla punctate. Metanotum weakly imbricate. Preëpisternum rugulose. Hypoepimeral area imbricate. Mesepisternum punctate (i=1=1–2d). Metepisternum with dorsal third carinulate, ventral portion imbricate. Metapostnotum with coarse striae, interstitial areas polished, posterior margin imbricate. Propodeum with lateral surface imbricate with weak oblique striae, posterior surface imbricate-tessellate. Metasomal terga polished, punctation on basal halves moderately sparse (i=2–3d), sparse on apical halves (i=2– 4d).

Structure. Head very wide (length/width ratio = 0.83). Eyes weakly convergent below (UOD/LOD ratio = 1.02). Labrum enlarged and flattened, apical process without dorsal keel. Mandible large with distinct preapical tooth. Clypeus 1/4 below suborbital tangent, apicolateral margins convergent. Antennal sockets moderately close (IAD/OAD <0.6). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Gena much wider than eye. Pronotal dorsolateral angle acute. Pronotal ridge carinate. Basitibial plate lower carina present. Inner metatibial spur pectinate with 4 branches. Metapostnotum truncate (MMR ratio = 1.32), posterior margin sharply angled onto posterior surface. Propodeum with oblique carina virtually absent, lateral carina weak, not reaching dorsal margin. T5 medial specialized area reduced.

MALE. Unknown.

Range. Maryland and West Virginia ( Fig. 92 ).

Paratype. USA: WEST VIRGINIA: 1Ƥ Hardy County, 7–27.vi.2007; [CUIC].

Etymology. The specific epithet is derived from the Latin work for “ cuckoo ”.

Barcode. Not available.

Comments. Rare. Lasioglossum curculum is only known from two specimens collected 42 years apart.

Lasioglossum curculum is likely a social parasite or cleptoparasite of nest-building Lasioglossum (Dialictus) .

Figures

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

FIGURE 90. Lasioglossum curculum Gibbs female, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 91. Lasioglossum curculum Gibbs female, dorsal view of mesosoma.

FIGURE 92. Distribution map of Lasioglossum curculum (stars) and L. disparile (circles).