Structure. Head elongate (length/width ratio = 1.031.06). Eyes convergent below (UOD/LOD ratio =
1.151.23). Clypeus ½ below suborbital tangent, apicolateral margins convergent. Antennal sockets close
(IAD/OAD < 0.5). Frontal line carinate, ending 2 OD below median ocellus. Gena narrower than eye. Inner
metatibial spur pectinate with 4 teeth. Metapostnotum truncate (MMR ratio = 1.361.45), posterior margin
weakly angled onto posterior surface. Propodeum with oblique carina fine, lateral carina short, not reaching
Range. Nova Scotia, Maine west to Ontario, Michigan (Fig. 135).
Additional material examined. CANADA: NEW BRUNSWICK: 2♀♀ Kent Co., St. Ignace, N46.707
W071.054, 31.vii.2005 (M. Gravel); NOVA SCOTIA: 1♀ Kings Co., Up Canard, N45.135 W064.489,
17.v.2003 (C. Sheffield); ONTARIO: 1♀ QUBS, 614.viii.2005 (L. Packer); [PCYU].
Floral records. Additional records attributed to L. pilosum likely apply to this species. ASTERACEAE:
Solidago, ROSACEAE: Crataegus coccinea.
Comments. Common. Lasioglossum leucocomum has long been considered a synonym of L. pilosum
(Michener 1951). Lovell (1908) described it as a variant of L. pilosum. DNA barcodes corroborate the morphological
characters recognised by Lovell (1908). Sequence divergence between L. leucocomum and L. pilosum
is approximately 8%. Indeed, the molecular data suggests a stronger similarity to L. succinipenne and L.
Extracted from Jason Gibbs. 2011. Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini.) Zootaxa.
Lasioglossum (Dialictus) leucocomum (Lovell)
Halictus pilosus var. leucocomus Lovell, 1908: 37. ♀.
Lectotype. ♀ USA, Maine, Waldoboro, 28.v.1905 (J.H. Lovell); [NMNH: 71569] designated herein. Examined.
Dialictus otsegoensis Mitchell, 1960: 440. ♂. [new synonymy]
Holotype. ♂ USA, Michigan, Ostego Co., 724.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 ♀, p. 175 (redescription, key).
Diagnosis. Female L. leucocomum can be recognised by the following diagnostic combination: head elongate
(length/width ratio = 1.031.06), clypeus with apicolateral margins strongly convergent, supraclypeal area relatively short
(0.650.86X 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 (0.800.90X 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 4.255.13 mm;
head length 1.321.63 mm; head width 1.221.45 mm; forewing length 3.443.75 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, T2T3 basolaterally and
T4 basally with sparse tomentum. S2S3 entirely and S4S5 laterally with posteriorly directed hairs (11.5OD).
Surface sculpture. Clypeal punctation moderately dense (i=12d). 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 = 1.081.12). 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 1.61.8X F1. F2F10
moderately elongate (length/width ratio = 1.381.63). Metapostnotum truncate (MMR ratio = 1.251.33), 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: 1♀ 5.viii.1957 (W.R. Richards); [CNC].
DNA Barcode. Available. Multiple haplotypes.
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