Lasioglossum (Dialictus) obscurum (Robertson)

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 155

Lasioglossum (Dialictus) obscurum (Robertson)

Halictus obscurus Robertson 1892: 270 . Ƥ.

Lectotype. Ƥ USA, Illinois, Macoupin Co., Carlinville, 8.v.1891 (C. Robertson); [INHS: 10959] by W. E. LaBerge (in Webb 1980). Examined.

Taxonomy. Robertson, 1902b: Chloralictus obscurus , p. 249 (key); Viereck 1916: Halictus (Chloralictus) obscurus , p. 707 (key); Michener, 1951: Lasioglossum obscurum , p. 1115 (catalogue); Mitchell, 1960: Dialictus obscurus Ƥ, p. 376 (redescription); Krombein, 1967: Lasioglossum (Dialictus) obscurum , p. 465, (catalogue); Hurd, 1979: Dialictus obscurum , p. 1969, (catalogue); Moure & Hurd, 1987: Dialictus obscurus , p. 117, (catalogue); Gibbs, 2010b: Lasioglossum (Dialictus) obscurum Ƥ3, p. 215 (redescription, key, synonymy).

Diagnosis. Female L. obscurum can be recognised by the following diagnostic combination: mesoscutal punctures sparse throughout, mesepisternal punctures distinct ( Fig. 24 A), propodeal carinae weak, and metasomal terga without tomentum but with very sparse apical fringes. They are superficially similar to L. nigroviride and L. tenax . Female L. nigroviride have moderately strong propodeal carinae and no fringe hairs on metasomal terga. Female L. tenax have dense punctures on the lateral portions of the mesoscutum.

Male L. obscurum can be recognised by the following diagnostic combination: head moderately elongate (length/ width ratio = 1.02–1.05); flagellomeres elongate (length/width ratio = 1.50–1.92); postgena imbricate; mesoscutum imbricate, punctures sparse (i=1–4d), denser laterad of parapsidal line (i=1–1.5d); mesepisternum punctate; apical impressed areas of metasomal terga impunctate; and S3–S5 apicolateral portions with sparse plumose hairs. They are similar to L. nigroviride , L. cattellae , L subversans , and L. tenax . Males of L. nigroviride and L. subversans have distinctly dense plumose hairs on the metasomal sterna. Male L. tenax have obscure mesepisternal punctures and the punctures of the metasomal terga limited to the basal portions and the premarginal lines. Male L. cattellae are small (4.3–4.5 mm), with coarse mesoscutal and mesepisternal punctures, and distinctly lineolate postgena.

Range. Ontario, south to North Carolina, west to Wisconsin. USA: CT, GA, IL, MD, MN, MI, MO, NC, NH, NY, OH, PA, TN, VT, WI, WV. CANADA: ON.

DNA Barcode. Available. Multiple sequences.

Comments. Common.

Figures

FIGURE 24. Mesepisternum (A) punctate, (B) impunctate (rugulose). (From Gibbs 2010 b).