Lasioglossum (Dialictus) nymphaearum (Robertson)

Halictus palustris Robertson, 1890: 317 . Ƥ 3. (primary junior homonym of Halictus palustris Morawitz, 1876)

Syntypes. [ANSP]. Examined.

Halictus nymphaearum Robertson, 1895: 117 (replacement name for H. palustris Robertson). Halictus paludicola Dalla Torre, 1896: 75 (replacement name for H. palustris Robertson). Halictus oceanicus Cockerell, 1916: 11 . Ƥ.

Holotype. Ƥ USA, New Jersey, Ocean Grove, 12.vii.1893, [NMNH: 27769]. Examined. Dialictus advertus Mitchell, 1960: 433 . 3.

Holotype. 3 USA, Massachusetts, Reading, 23.vii.1933 (R. Dow); [NCSU]. Examined.

Taxonomy. Robertson, 1902b: Chloralictus nymphaearum, p. 248 (key); Viereck, 1916: Halictus (Chloralictus) nymphaearum, p. 706; Michener, 1951: Lasioglossum (Chloralictus) nymphaearum, p. 1115 (catalogue, synonymy); Mitchell, 1960: Dialictus nymphaearum Ƥ3, p. 407 (redescription); Krombein, 1967: Lasioglossum (Dialictus) advertum, p. 462, L. (D.) nymphaearum, p. 465 (catalogue); Hurd, 1979: Dialictus advertus, p. 1963, D. nymphaearum, p. 1969 (catalogue); Moure & Hurd, 1987: Dialictus advertus, p. 102, D. nymphaearum, p. 116 (catalogue); Gibbs, 2010b: Lasioglossum (Dialictus) oceanicum Ƥ3, p. 220 (redescription, key, synonymy).

Diagnosis. Female L. nymphaearum can be recognised by the following diagnostic combination: size large (6.0– 7.5 mm), hypostomal carina distally reflexed, mesoscutal punctures coarse (i=1–1.5d), metapostnotum with posterior dorsal margin carinate, and apical impressed areas of metasomal terga densely punctate

Male L. nymphaearum are similar to females but have hypostomal carina normal and transverse carina bordering metapostnotum dorsal surface distinctly bowed posteriorly. Male L. nymphaearum can be further distinguished by face below emargination with dense tomentum, head moderately elongate (length/width ratio = 0.97–1.00), and flagellomeres short (length/width ratio = 1.13–1.33). They are most similar to L. albipenne, which lacks distinct punctures on the tegula and have a longer head (length/width ratio = 0.99–1.08).

Range. Nova Scotia west to Ontario, Minnesota, south to North Carolina. USA: CT, IL, IN, KS, MA, MD, MI, MN, MO, NC, NJ, NY, OK, PA, RI, TX, VA, WI, WV. CANADA: ON.

DNA Barcode. Available. Multiple sequences.

Comments. Common.

The syntype series of Halictus palustris includes both L. nymphaearum as it is usually applied (e. g. Mitchell 1960) and L. albipenne . An invalid lectotype for Halictus palustris at ANSP (specimen number 4252) belongs to the latter species. Gibbs (2010b) considered this lectotype to be valid and as a result made Halictus nymphaearum a junior subjective synonym of L. albipenne . Gibbs (2010b) then applied the name L. oceanicum for the species traditionally called L. nymphaearum . Since it is now clear the lectotype for Halictus palustris at the ANSP is invalid (no published designation can be found), the standard usage of L. nymphaearum is applied herein to maintain nomenclatural stability. It is clear from Robertson’s (1890) original description that he did not mean for Halictus palustris to apply to L. albipenne, which he describes in the same paper. The syntype series at ANSP includes specimens of L. nymphaearum as currently (and historically) applied. One of these will be designated as the lectotype to fix the name to a single species and maintain standard usage of L. nymphaearum .