Robertson 1892 : 270 Chloralictus obscurus Halictus ( Chloralictus ) obscurus Lasioglossum obscurum Dialictus obscurus Lasioglossum ( Dialictus ) obscurum Dialictus obscurum Dialictus obscurus Lasioglossum ( Dialictus ) obscurum Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini) Gibbs, Jason Zootaxa 2011 2011-10-28 3073 1 216 6P2DH Robertson Robertson [151,738,1015,1041] Insecta Halictidae Lasioglossum Animalia Hymenoptera 154 155 Arthropoda species obscurum Dialictus     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 obscurusƤ, 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) obscurumƤ3, p. 215 (redescription, key, synonymy).   Diagnosis.Female  L. obscurumcan be recognised by the following diagnostic combination: mesoscutal punctures sparse throughout, mesepisternal punctures distinct ( Fig. 24A), propodeal carinae weak, and metasomal terga without tomentum but with very sparse apical fringes. They are superficially similar to  L. nigrovirideand  L. tenax. Female  L. nigroviridehave moderately strong propodeal carinae and no fringe hairs on metasomal terga. Female  L. tenaxhave dense punctures on the lateral portions of the mesoscutum.  Male  L. obscurumcan 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. nigrovirideand  L. subversanshave distinctly dense plumose hairs on the metasomal sterna. Male  L. tenaxhave obscure mesepisternal punctures and the punctures of the metasomal terga limited to the basal portions and the premarginal lines. Male  L. cattellaeare 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.