Identification Summary: Large; hypostomal carina reflexed distally; blue thorax; rim of propodeal triangle sharply defined by a raised line or carina that runs across the entire edge and is almost completely straight; abdomen relatively hairy with lots of appressed hairs.
Reprinted with permission from: Mitchell, T.B. 1960 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 141.
FEMALE—Length 7 mm.; head and thorax olive green, abdomen darker but with strong metallic greenish reflections; pubescence short, thin, entirely whitish, abdomen posteriorly more or less covered with appressed tomentum; head slightly broader than long; clypeus broadly convex, projecting about one-half below suborbital line; supraclypeal area slightly convex, slightly broader than long, and only very slightly shorter than clypeus; eyes convergent below; lateral ocelli slightly nearer eyes than each other; cheeks subequal to eyes in width; face below ocelli closely, deeply and rather coarsely punctate medially, punctures becoming finer and more irregular laterally, more minute and irregular on shining vertex; cheeks above shining, punctures exceedingly minute but close, becoming finely striate below; hypostomal carinae subparallel, apical angle rather abrupt, but quite strongly produced; lower half of face somewhat shining, punctures deep and distinct, well separated but not sparse, those on supraclypeal area slightly finer at sides but well separated medially, those on upper margin of clypeus rather fine and close but deep and distinct, becoming more coarse and well separated apically, the apical two-thirds blackened; scutum and scutellum somewhat shining, punctures rather widely separated on scutum medially (fig. 99), becoming quite close but not crowded laterally, those on scutellum rather fine and close in midline, rather widely scattered on side; pleura rather coarsely rugose above and anteriorly, becoming more finely rugoso-striate posteriorly; dorsal area of propodeum coarsely and regularly striate, posterior face completely encircled with a salient rim, rather smooth, lateral faces rather dull, more or less finely striate around margins, somewhat smoother medially; wings hyaline, veins and stigma testaceous; tegulae piceous, becoming narrowly yellowish-hyaline on anterior margin; legs piceous, not appreciably paler apically; abdominal terga shining, basal tergum with minute, scattered, but rather distinct punctures, terga 2 and 3 somewhat more closely punctate across base, these continuing to the apical impressed area, this rather broad and shallow, becoming narrowly whitish-hyaline on apical margin, terga 3 and 4 partially obscured by thin, pale tomentum, interspersed with longer more erect hairs.
MALE—Length 6.5—7.0 mm.; head and thorax olive green, abdomen blackish; pubescence short, thin, entirely white, quite dense on head, rather copious on thorax laterally and across metanotum; length and breadth of head subequal; clypeus rather narrow, projecting somewhat more than one-half below suborbital line; supraclypeal area subequal in length to clypeus; eyes strongly convergent below; lateral ocelli nearer eyes than to each other; antennae slightly nearer eyes than to each other, basal segment of flagellum slightly longer than pedicel, length and breadth sub- equal, 2nd and following segments considerably longer, but not nearly twice as long as broad, brownish-ferruginous beneath, more piceous above; cheeks slightly narrower than eyes; face below ocelli deeply, distinctly and uniformly closely punctate, punctures rather fine, becoming minute and indistinct on the shining vertex; cheeks shining above, punctures rather fine and close but obscure, becoming finely and rather distinctly striate below; hypostomal carinae subparallel, apical angle very slightly produced; lower half of face rather closely and finely but deeply and distinctly punctate beneath the dense white tomentum; scutum and scutellum somewhat shining, punctures rather sparse on scutum medially, becoming almost crowded between notaulices and tegulae, scutellum rather deeply grooved medially, somewhat protuberant on each side, punctures irregularly scattered but rather deep and distinct; pleura dull, finely rugoso-striate; dorsal area of propodeum very coarsely rugoso-striate medially, becoming somewhat more regularly striate laterally; posterior face almost completely encircled with a salient rim, this interrupted briefly on each side above, rather coarsely reticulate, lateral faces dull, very finely rugoso-striate; wings hyaline, veins and stigma brownish-testaceous; tegulae brownish-testaceous, becoming more clear hyaline anteriorly; legs piceous basally, front tibiae narrowly testaceous basally and apically, all tarsi yellowish; abdominal terga shining, discs quite closely and distinctly but very finely punctate, apical margins rather narrowly impressed, this area completely impunctate, becoming somewhat brownish toward rims, pubescence in general quite thin, not at all obscuring the surface; apical margin of sternum 5 straight; median process of sternum 7 subtruncate, length less than twice the breadth; gonostylus of armature as shown (fig. 102), retrorse lobe rather expansive, very sparsely covered with short, fine pubescence.
DISTRIBUTION—Minnesota to Nova Scotia, south to Georgia; May to September.
FLOWER RECORDS—Asclepias, Barbarea, Berteroa, Castalia, Chrysanthemum, Daucus, Fagopyrum, Hydrangea, Koellia, Krigia, Lotus, Lythrum, Medicago, Melilotus, Pontederia, Potentilla, Ranuneulus, Rubus, Solidago, Taraxacum and Trifolium. Robertson (1929) records nymphaearum on Lippia, Nelumbo, Salix and Taenidia. Brittain and Newton (1934) record it on Leontodon.
Extracted from Jason Gibbs. 2011. Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini.) Zootaxa.
Lasioglossum (Dialictus) nymphaearum (Robertson)
Halictus palustris Robertson, 1890: 317. ♀ ♂. (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. ♀.
Holotype. ♀ USA, New Jersey, Ocean Grove, 12.vii.1893, [NMNH: 27769]. Examined.
Dialictus advertus Mitchell, 1960: 433. ♂.
Holotype. ♂ 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 ♀♂, 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 ♀♂, 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.
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.