Lasioglossum

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 11-12

Diagnosis for Lasioglossum (Dialictus) in eastern North America

Lasioglossum (Dialictus) are small (3.1–8.1 mm), andreniform bees, which can be separated from most other bees in eastern North America by the following combination of characters: basal vein strongly arched, distal veins of forewing weak (1rs-m, 2rs-m, 2m-cu, and the distal abscissa of M; 1rs-m sometimes absent) ( Fig. 5 ), and female inner metatibial spur pectinate with long branches.

Most species of L. ( Dialictus ) have metallic reflections of the head and mesosoma that distinguishes them from all other Lasioglossum s. l. in eastern North America. Additional characters that further assist in distinguishing Dialictus from other eastern North American Lasioglossum subgenera are as follows. Lasioglossum s. s. and L. (Leuchalictus) have vein 1rs-m strong and are typically much larger than Dialictus . Female L. (Hemihalictus) have a serrate inner metatibial spur and both sexes usually lack vein 1rs-m. Female L. ( Sphecodogastra ) have a unique metafemoral scopa consisting of a single linear series of coarse hairs.

The subgenus L. ( Evylaeus ) is the most difficult to distinguish from L. ( Dialictus ) with black integument. Female Evylaeus may have the inner metatibial spur serrate, denticulate, or pectinate but the branches are usually shorter than those of Dialictus . Male Evylaeus have the inner dorsal margins of the gonocoxites parallel basally for over 1/2 to 2/3 their length and are widely divergent apically. Lasioglossum (Evylaeus) in eastern North America usually have lateral and posterior surfaces of propodeum completely separated by lateral propodeal carinae and mesepisternum rugulose.

In contrast, all female L. ( Dialictus ) in eastern North America have pectinate inner metatibial spurs with long branches and all male L. ( Dialictus ) have the inner dorsal margins of the gonocoxites more evenly and weakly divergent over their entire length (except L. (D.) rufulipes and L. (D.) testaceum ). Black Dialictus may have the mesepisternum distinctly punctate or very coarsely rugose which is never seen in eastern Evylaeus . Female black Dialictus with weak mesepisternal sculpture have lateral and posterior surfaces of propodeum incompletely separated by the lateral propodeal carinae. Species of black Dialictus with lateral and posterior propodeal surfaces completely separated (e. g. L. pectorale (Smith)) are always more coarsely sculptured on the mesosoma than Evylaeus .

Figures

FIGURE 5. Forewings of female Lasioglossum subgenus Dialictus. (A) Typical forewing with three submarginal cells. Pterostigma (pt), basal vein (b), arrows indicate weakened veins. (B) Forewing with two submarginal cells. Arrows indicate weakened veins. (From Gibbs 2010 b).