Lasioglossum (Dialictus) leucocomum (Lovell)

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 130-131

Lasioglossum (Dialictus) leucocomum (Lovell)

Halictus pilosus var. leucocomus Lovell, 1908: 37 . Ƥ.

Lectotype. Ƥ USA, Maine, Waldoboro, 28.v.1905 (J.H. Lovell); [NMNH: 71569] designated herein. Examined. Dialictus otsegoensis Mitchell, 1960: 440 . 3. [new synonymy]

Holotype. 3 USA, Michigan, Ostego Co., 7–24.vii.1955 (R.R. Dreisbach); [ NCSU]. Examined.

Taxonomy. Krombein, 1967: Lasioglossum (Dialictus) otsegoense , p. 465 (catalogue); Dialictus otsegoensis , p. 1969 (catalogue); Moure & Hurd, 1987: Dialictus otsegoensis , p. 118 (catalogue); Gibbs, 2010b: Lasioglossum (Dialictus) leucocomum Ƥ, p. 175 (redescription, key).

Diagnosis. Female L. leucocomum can be recognised by the following diagnostic combination: head elongate (length/width ratio = 1.03–1.06), clypeus with apicolateral margins strongly convergent, supraclypeal area relatively short (0.65–0.86X clypeal length), mesoscutal punctures contiguous, metapostnotum rugoso-carinulate, and metasomal terga metallic with dense yellowish tomentum. They are most similar to L. pilosum and L. succinipenne . Female L. pilosum have the apicolateral margins of the clypeus subparallel. Female L. succinipenne have the supraclypeal area relatively long (0.80–0.90X clypeal length) and dense whitish tomentum on the metasomal terga.

Male L. leucocomum can be recognized by the combination of head elongate, clypeus yellow distally, mesoscutal punctures dense but distinctly separated medially, metasomal terga metallic. They are most similar to L. pilosum which have the mesoscutal punctures contiguous medially.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 4.25–5.13 mm; head length 1.32–1.63 mm; head width 1.22–1.45 mm; forewing length 3.44–3.75 mm.

Colouration. Labrum yellow. Mandible yellow. Clypeus distal margin yellow. Flagellum with ventral surface orange. Legs brown, except bases and apices of tibiae and tarsi yellow.

Pubescence. Moderately dense. Face below eye emargination with tomentum partially obscuring surface, dense on lower paraocular area. T1 acarinarial area with sparse fan of appressed hairs. T1 dorsolaterally, T2–T3 basolaterally and T4 basally with sparse tomentum. S2–S3 entirely and S4–S5 laterally with posteriorly directed hairs (1–1.5OD).

Surface sculpture. Clypeal punctation moderately dense (i=1–2d). Mesoscutal punctures distinctly separated medially (i=d). Mesepisternum reticulate-rugulose. Propodeum with dorsolateral slope and lateral and posterior surfaces rugulose. Metasomal terga punctation deep, distinct.

Structure. Head very elongate (length/width ratio = 1.08–1.12). Eyes convergent below (UOD/LOD ratio = 1.43– 1.52). Clypeus 2/3 below suborbital tangent, apicolateral margins subparallel. Antennal sockets distant (IAD/OAD = 1.0). Frontal line carinate, ending 2OD below median ocellus. Pedicel subequal to F1. F2 length 1.6–1.8X F1. F2–F10 moderately elongate (length/width ratio = 1.38–1.63). Metapostnotum truncate (MMR ratio = 1.25–1.33), posterior margin weakly angled onto posterior propodeal surface.

Terminalia . Not examined.

Range. Nova Scotia, Maine west to Minnesota, south to Appalachian mountains of North Carolina. USA: CT, IN, MA, ME, MI, MN, NC, NH, NJ, NY, WI. CANADA: NB, NS, ON, PE.

Additional material examined. USA: NORTH CAROLINA: 1Ƥ 5.viii.1957 (W.R. Richards); [ CNC].

DNA Barcode. Available. Multiple haplotypes.

Comments. Common.

Until recently, L. leucocomum had never been considered more than a subspecies of L. pilosum ( Gibbs 2010b) . Attempts to separate the males of L. pilosum and L. leucocomum using DNA barcoding have consistently failed to produce L. leucocomum sequences. Morphological study of L. pilosum s. l., however, has revealed variability in mesoscutal puncture density. It is now believed, based on geographical patterns of co-occurence with females, that the males with sparser punctures are actually L. leucocomum . The holotype of D. otsegoense , considered by Gibbs (2010b) to be a junior synonym of L. pilosum , is of this form.

The name-bearing type has lectotype labels from both Mitchell and Covell. No publication by either of these authors could be found that makes a valid lectotype designation. Lasioglossum leucocomum was recently resurrected from synonymy with L. pilosum by Gibbs (2010b). To maintain stability of usage, the specimen indicated above is designated as the lectotype.