Extracted from: Gibbs, J., Packer, L., Dumesh, S. and Danforth, B. N. 2013. Revision and reclassification of Lasioglossum (Evylaeus), L. (Hemihalictus) and L. (Sphecodogastra) in eastern North America (Hymenoptera: Apoidea: Halicidae). Zootaxa 3672 (1). Pp 1-116.
Diagnosis. Female L. seillean can be recognised by the combination of head long (L/W ratio = 1.02–1.04)
(Fig. 43G); mesepisternum finely rugulose (as in Fig. 76D); inner metatibial spur pectinate, basal teeth longer than
width of rachis (Fig. 5P); propodeum with lateral carina distinct, extending to dorsal margin, oblique carina strong
(Fig. 79F); T1 dull due to microsculpture; and T2–T3 without dense apical fimbriae (Fig. 81D). In the east, L.
seillean is most similar to L. boreale, L. comagenense, and L. quebecense. Lasioglossum boreale and L.
comagenense have short teeth on the inner metatibial spur, not exceeding the width of the rachis (Figs. 5M, 5N)
and T1 polished due to lack of microsculpture (Figs. 81A, 81B). Lasioglossum comagenense has a noticeably
shorter head (L/W ratio = 0.93–0.96) (Fig. 43C). The female of L. boreale has fine propodeal carinae (Fig. 79C).
Lasioglossum seillean is nearly indistinguishable from L. quebecense but averages smaller in size (5.8–6.5 mm vs.
6.5–7.0 mm).
Male L. seillean can be recognised by the combination of clypeus with yellow on distal half (Fig. 44G);
mandible short, not extending much beyond opposing clypeal angle; F2 long, subequal to scape; propodeal lateral
carina strong; metasomal sterna nearly bare, hairs present but very short (as in Fig. 85A); S2–S3 with sparse punctures (as in Fig. 88A); metatibial base brown or with small yellow spot; and basitarsi bright yellow (Fig. 69).
Males of L. boreale and L. comagenense have a large yellow patch on the metatibial base (Figs. 54, 57). The
clypeal maculation is smaller on L. seillean (Fig. 44G) than on L. boreale, L. comagenense and L. quebecense
(Figs. 44B, 44C, 44F). The unique shape of the retrorse lobe (Figs. 87D, 87F), which is long, gently curved,
parallel-sided to a rounded apex, is the most reliable character for distinguishing L. seillean males from L. boreale,
L. comagenense, and L. quebecense (Figs. 87A, 87B, 87C, 87E).
Description. FEMALE. Length 5.8–6.5 mm. Head length 1.67–1.91 mm. Head width 1.61–1.88 mm. Wing
length 4.6–5.4 mm. (n=3)
Colour. Head and mesosoma black. Antenna black, except ventral surface of flagellum reddish brown-orange.
Tegula dark reddish brown. Legs dark brown, except medio- and distitarsi reddish brown. Wing membrane hyaline,
faintly dusky. Pterostigma orange-brown. Metasomal terga black-brown.
Structure. Head long (L/W ratio = 1.02–1.04). Clypeus 1/2 - 2/3 below suborbital line. Eyes convergent below
(UOD:LOD = 1.09–1.16). Gena subequal to eye width. Ocelli normal. Pronotum smoothly rounded. Protibial spur
with apical serrations as long as width of malus. Inner metatibial spur pectinate, teeth six, basal teeth slightly
longer than width of rachis. Propodeal lateral carina reaching dorsal margin, oblique carina high, separating
dorsolateral slope from posterior surface.
Surface sculpture. Supraclypeal area polished medially, punctures sparse (i=1–2.5d). Gena lineolate, postgena
smoother. Mesoscutum weakly imbricate to polished; punctures dense (i≤d), except posteromedially (i=1–1.5d).
Mesepisternum finely rugulose, smoother ventrally. Metapostnotum carinate-rugose. Propodeum imbricatetessellate. Metasomal terga mostly coriarious, T1 polished; punctures dense, sparser posteromedially, T2 apical
impressed area impunctate medially.
Pubescence. Head and mesosoma with sparse plumose hairs. Metafemoral scopa with dense plumose hairs.
Metasomal terga with relatively dense, medially-interrupted apical fimbriae. T1 with sparse, erect plumose hairs.
T2–T4 basally with sparse, tomentum. Metasomal sterna with plumose scopa.
MALE. Length 5.9–7.0 mm. Head length 1.62–1.88 mm. Head width 1.55–1.80 mm. Wing length 4.2–4.9
mm. (n=3)
Colour. Head and mesosoma black. Clypeus yellow apically. Mandible brown. Labrum yellow basally.
Antenna black, except ventral surface of flagellum orange, less so on F10–F11. Legs dark brown, except tarsi and
apex of protibia yellow, anterior surface of protibia infused with testaceous, metatibia rarely with small yellow
spot. Wing membrane hyaline. Pterostigma orange-brown. Metasomal terga dark brown, apical margins pale
brown.
Structure. Head long (L/W ratio = 1.04–1.06). Clypeus 2/3–3/4 below suborbital tangent. Mandible short,
reaching opposing clypeal angle. Flagellomeres, except F1, elongate, F2 longer than F1 and pedicel combined.
Eyes strongly convergent below (UOD:LOD = 1.2 8–1.46). Gena clearly narrower than eye. Pronotum smoothly
rounded. Propodeal lateral carina reaching dorsolateral slope.
Surface sculpture. Supraclypeal area imbricate, with sparse, shallow punctures (i=1–1.5d). Gena and postgena
lineolate. Mesoscutum weakly polished, reticulate anteriorly; punctures dense (i≤d) but clearly separated
posteromedially (i=1–1.5d). Mesepisternum rugulose, weakly so ventrally. Metapostnotum anastomosingly rugose.
Propodeum rugulose, posterior surface rugose. Metasomal terga polished; punctures deep, close basally. T2–T6
apical impressed areas impunctate. Metasomal sterna sparsely, obscurely punctate (i=2–5d).
Pubescence. Head and mesosoma with sparse plumose hairs. Face below antennal sockets with dense
tomentum, lower paraocular area obscured, supraclypeal area and clypeus partially obscured, clypeus bare on distal
half. Propodeum largely bare, with scattered plumose hairs. Metasomal terga nearly bare, without apical fimbriae.
T2 with narrow, basolateral patch of tomentum. Metasomal sterna nearly bare, with sparse, short, plumose hairs
(≤1 OD).
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