Identification Summary: Large; metallic green-gold; scutum with large pits; rear face of propodeum has lateral carinae that come up the sides and curve over the top bordering the propodeal triangle but do not meet in the center, overall this gives the impression of a carinate heart; appressed hairs on abdomen often slightly long and tinged with brown; cheeks heavily striated; mesepisturnum very rugose.
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 6.5 mm.; head and thorax brassy-green, abdomen piceous; head somewhat broader than long; clypeus broadly convex, projecting about one-half below suborbital line; supraclypeal area somewhat broader than long and shorter than clypeus; eyes convergent below; lateral ocelli nearer eyes than to each other; cheeks subequal to eyes in width; face below ocelli rather dull, punctures coarse, deep and distinct, very close medially, becoming somewhat more definitely separated at extreme sides, those on the shining vertex becoming very fine and irregularly scattered; cheeks above rather dull, almost entirely coarsely striate; hypostomal carinae subparallel, apical angle rather narrowly rounded; lower half of face somewhat shining, punctures quite deep, distinct and coarse, definitely but not widely separated, those on supraclypeal area somewhat finer and rather close laterally, becoming well separated but not sparse medially, those along upper margin of clypeus rather fine and close, becoming more coarse, deep and sparse apically, the apical half blackened; scutum rather dull, punctures deep and distinct, similar to nymphaearum, (fig. 99), but closer in antero-lateral areas; scutellum very densely and finely rugoso-punctate medially, becoming more distinctly and coarsely punctate laterally, with some interspaces evident; pleura coarsely reticulate anteriorly and above, becoming somewhat more finely striate posteriorly; dorsal area of propodeum rather coarsely striate laterally, the median portion more irregularly rugoso-striate, posterior face completely encircled by a low salient rim, surface irregularly rugoso-striate, lateral faces rather dull, finely rugoso-striate; wings hyaline, veins and stigma testaceous; tegulae brownish-testaceous, becoming more yellowishhyaline anteriorly; legs piceous, becoming more or less brownish-testaceous apically; abdominal terga 1 and 2 shining, very finely but quite distinctly punctate, but the impressed, apical areas largely impunctate, these areas concolorous with the basal portions of discs, tergum 2 densely pale tomentose toward sides basally, 3 and 4 almost completely obscured with the dense, pale yellowish tomentum.
MALE—Length 6 mm.; head and thorax dark olive green, becoming more or less bluish in certain areas, abdomen blackish; pubescence short, thin, entirely white, more dense on face; length and breadth of head subequal; clypeus rather narrow, projecting slightly more than one-half below suborbital line; supraclypeal area about as long as broad and subequal in length to clypeus; eyes strongly convergent below; lateral ocelli subequally distant from eyes and each other; antennae very slightly nearer eyes than to each other, basal segment of flagellum slightly longer than pedicel, about as broad as long, the 2nd and following segments nearly twice as long, uniformly piceous; cheeks slightly narrower than eyes; face below ocelli dull, punctures fine and densely crowded, becoming distinct but minute and rather well separated on the shining vertex; cheeks shining above, becoming more striate below, but areas on each side of hypostomal carinae rather smooth, somewhat shining; hypostomal carinae parallel, apical angle abrupt; lower half of face closely and finely punctate, punctures on supraclypeal area more shallow and obscure but rather close, those on clypeus fine, distinctly separated but rather close in general, these areas often obscured by pale tomentum; scutum shining, punctures deep and distinct, well separated medially as well as between notaulices and tegulae, becoming rather close at sides anteriorly and across posterior margin, scutellum slightly grooved medially, this area rather closely punctate, punctures sparse on each side of this; pleura rather coarsely reticulate; dorsal area of propodeum coarsely and completely striate, posterior face almost completely encircled by a salient rim, this vestigial above, surface rather coarsely rugoso-striate, lateral faces rather dull, irregularly and finely rugoso-striate; wings subhyaline, veins and stigma brownish-testaceous; tegulae more brownish, anterior margin narrowly yellowish-hyaline; basal portions of legs piceous, tarsi almost completely testaceous; abdominal terga shining, basal tergum almost completely impunctate, punctures being exceedingly vague and minute, those on tergum 2 somewhat more distinct, but well separated across base, becoming impunctate apically, similar to terga 3 and 4, apical areas rather broadly but shallowly impressed, becoming very narrowly yellowish-hyaline on rims of terga 3 and 4, pubescence quite thin and sparse; apical margin of sternum 5 nearly straight; median process of sternum 7 much as in reticukitus (fig. 101) ; 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; March to October.
FLOWER RECORDS—Acer, Althaea, Apocynum, Azalea, Barbarea, Berteroa, Brassica, Chrysanthemum, Cirsium, Claytonia, Daucus, Euonymus, Fagopyrum, Geranium, Houstonia, Hydrangea, hex, Melilotus, Pedicularis, Potentilla, Rubus, Salvia, Solidago, Taraxacum, Vagnera and Viburnum. Robertson (1929) records cressonii on these additional genera: Alisma, Âmelanchier, Cacalia, Capsella, Chaerophyllum, Crataegus, Cryptotaenia, Hypoxis, Isopyrum, Ludwigia, Melilotus, Prunus, Ptelea, Ranunculus, Rhus, Ribes, Salix, Sassafras, Symphoricarpus, Virbascum, Viola and Zanthoxylum. Brittain and Newton (1933 & 1934) record it also on Amorpha, Philadelphus, Pyrus malus, Rhododendron and Vaccinium. A specimen of this species was received from K. V. Krombein which he and Padre
J. S. Moure found nesting in rotten heart wood in a live, standing oak at Plummer’s Island, Maryland.
Retrieved from: Gibbs, J. 2010. Revision of the metallic species of Lasioglossum (Dialictus)in Canada (Hymenoptera, Halictidae, Halictini). Zootaxa; 2591, 101-106
Halictus Cressonii Robertson, 1890: 317. ♀ ♂.
Holotype. ♀ USA, Massachusetts [ANSP: 4253]. Examined.
Dialictus delectatus Mitchell, 1960: 435. ♂. [new synonymy]
Holotype. ♂ USA, Maryland, Plummer’s Is., 13.ix.1958 (K.V. Krombein); [NMNH: 66072). Examined.
Halictus (Chloralictus) cressoni Viereck, 1916: 707 (Emend.)
Taxonomy. Robertson, 1902: Chloralictus Cressonii, p. 249 (key); Michener, 1951: Lasioglossum (Chloralictus)
cressonii, p. 1113 (catalogue); Mitchell, 1960: Dialictus cressonii ♀♂, p.390 (redescription); Krombein,
1967: Lasioglossum (Dialictus) cressonii, p. 463, L. (D.) delectatum, p. 463 (catalogue); Hurd, 1979: Dialictus
cressonii, p. 1965, D. delectatus, p. 1965 (catalogue); Moure & Hurd, 1987: Dialictus cressonii, p. 97, D.
delectatus, p. 99 (catalogue).
Diagnosis. Females of L. cressonii are recognisable by the diagnostic combination of golden green head
and mesosoma, coarse mesoscutal punctures which are moderately dense on the central disc (i=1=1.5d), the
very coarsely rugose mesepisternum (Fig. 92E), very strong propodeal carinae which form a medially interrupted
delineation between the dorsal and posterior surfaces of the propodeum (Fig. 92F), parallel and not
reflexed hypostomal carinae, faintly dusky wings and sparse punctures on the apical impressed areas of the
metasomal terga. They are most similar to L. albipenne and L. oceanicum. Female L. albipenne have a bluish
green head and mesosoma, sparse mesoscutal punctures (i=1–3d) and pale wings. Female L. oceanicum have
a bluish head and mesosoma, reflexed hypostomal carinae, an uninterrupted transverse propodeal carina, and
dense punctures on the apical impressed areas of the metasomal terga.
Males of L. cressonii share the same diagnostic traits as females but may be further recognised by the
elongate flagellomeres, F2–F10 length/width ratio = 1.69–1.83, and the punctate anterior margin of the
mesoscutum. They are most similar to those of L. bruneri and L. oceanicum. Male L. bruneri have the anterior
margin of the mesoscutum rugose. Male L. oceanicum have relatively short flagellomeres, F2–F10 length/
width ratio = 1.13–133, and distinctly punctate tegula.
Redescription. FEMALE. Length 5.19–6.80 mm; head length 1.46–1.75 mm; head width 1.49–1.82 mm;
forewing length 3.97–5.49 mm.
Colouration. Head and mesosoma pale green to golden green, with some bluish reflections. Clypeus with
apical half blackish brown. Antenna blackish brown, flagellum with ventral surface dark brown. Tegula dark
reddish brown. Wing membrane subhyaline, venation and pterostigma amber. Legs brown, medio- and distitarsi
reddish brown. Metasoma blackish brown, terga and sterna with apical margins reddish.
Pubescence. Dull to yellowish white. Moderately dense. Head and mesosoma with moderately dense
woolly hairs (1–1.5 OD), longest on genal beard, metanotum and mesopleuron (2–2.5 OD). Paraocular area
with sparse subappressed hairs. Gena without tomentum. Propodeum with dense plumose hairs on lateral and
posterior surfaces (2–2.5 OD). Metasomal terga with sparse, fine setae. T1 acarinarial fan complete. T2–T3
basolaterally and T4 entirely with dense tomentum partially obscuring surface. T2 apicolateral and T3–T4
apical margins with weak fringes.
Surface sculpture. Face imbricate, punctation coarse. Clypeus polished, basal margin imbricate, punctation
sparse (i=1–3d). Supraclypeal area with punctation moderately dense (i=1–2d). Lower paraocular and antennocular areas with punctation moderately dense (i=1–1.5d). Upper paraocular area and frons punctatereticulate.
Ocellocular area densely punctate (i
Structure. Head wide (length/width ratio = 0.96–0.97). Eyes convergent below (UOD/LOD ratio = 1.23–
1.29). Clypeus 1/2 below suborbital line, apicolateral margins convergent. Antennal sockets close (IAD/OAD
< 0.5). Frontal line carinate, ending 2.5 OD below median ocellus. Gena narrower than eye. Inner metatibial
spur pectinate with 3–5 teeth. Metapostnotum posterior margin sharply angled, nearly carinate. Metapostnotum
moderately elongate (MMR ratio = 1.25–1.30), posterior margin sharply angled onto posterior surface.
Propodeum with oblique carina very strong, lateral carina strong reaching dorsal margin.
MALE. Similar to female except for the usual secondary sexual characters and as follows. Length. 5.12–
6.30 mm; head length 1.61–1.70 mm; head width 1.54–1.70 mm; forewing length 3.97–4.58 mm.
Colouration. Tarsi yellow or yellowish brown.
Pubescence. Face with sparse subappressed tomentum, partially obscuring surface. Lower paraocular area
with dense tomentum. S2–S3 apical portions and S4 lateral portions with dense erect hairs (i=1.5–2 OD).
Surface sculpture. Metanotum rugose. Metasomal terga uniformly punctate (i=2–2.5d), apical impressed
Structure. Head moderately elongate (length/width ratio = 1.00–1.05). Eyes strongly convergent below
(UOD/LOD ratio = 1.50–1.63). Clypeus 2/3 below suborbital line, apicolateral margins subparallel. Antennal
sockets distant (IAD/OAD > 1.1). Frontal line carinate, ending 2 OD below median ocellus. Pedicel shorter
than F1. F2 length 1.8–2.0X F1. F2–F10 elongate (length/width ratio = 1.69–1.83). Metapostnotum truncate
(MMR ratio = 1.38–1.50), posterior margin sharply angled onto posterior surface. Propodeum with less evident
oblique and lateral carinae.
Terminalia. S7 with median lobe weakly clavate, sides weakly convex, apex rounded (Fig. 93F). S8 with
apicomedial margin strongly convex (Fig. 93F). Genitalia as shown in Fig. 93D–E. Gonobase with ventral
arms thick, narrowly separated. Gonostylus narrow and elongate, dorsal setae elongate. Retrorse lobes elongate,
Range. Nova Scotia west to British Columbia, south to Georgia and Colorado
Extracted from Jason Gibbs. 2011. Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini.) Zootaxa.
Lasioglossum (Dialictus) cressonii (Robertson)
Halictus Cressonii Robertson, 1890: 317. ♀ ♂.
Lectotype. ♀ USA, Massachusetts [ANSP: 4253] designated herein. Examined.
Dialictus delectatus Mitchell, 1960: 435. ♂.
Holotype. ♂ USA, Maryland, Plummer’s Is., 13.ix.1958 (K.V. Krombein); [NMNH: 66072). Examined.
Halictus (Chloralictus) cressoni Viereck, 1916: 707 (emend.).
Taxonomy. Robertson, 1902b: Chloralictus Cressonii, p. 249 (key); Michener, 1951: Lasioglossum (Chloralictus) cressonii,
p. 1113 (catalogue); Mitchell, 1960: Dialictus cressonii ♀♂, p.390 (redescription, key); Krombein, 1967: Lasioglossum
(Dialictus) cressonii, p. 463, L. (D.) delectatum, p. 463 (catalogue); Hurd, 1979: Dialictus cressonii, p. 1965, D.
delectatus, p. 1965 (catalogue); Moure & Hurd, 1987: Dialictus cressonii, p. 97, D. delectatus, p. 99 (catalogue); Gibbs,
2010b: Lasioglossum (Dialictus) cressonii ♀♂, p. 101 (redescription, key, synonymy).
Diagnosis. Female L. cressonii are recognisable by the following diagnostic combination: head and mesosoma
golden green; hypostomal carinae parallel, unreflexed; mesoscutal punctures very coarse, moderately dense between
parapsidal lines (i=1=1.5d) (Fig. 4B); mesepisternum very coarsely rugose; propodeal carinae strong, lateral carina reaching
dorsal surface (Fig. 2A); and metapostnotum with posterior margin sharply angled. They are easily distinguished
from L. bruneri and L. reticulatum, which have divergent hypostomal carinae. Female L. albipenne have relatively sparse mesoscutal punctures (i=1–3d) and noticeably pale wings. Female L. nymphaearum have hypostomal carinae reflexed
distally and metapostnotum with posterior carina uninterrupted.
Male L. cressonii are similar to females but may be further recognised by clypeal hairs not obscuring surface,
flagellomeres elongate (length/width ratio = 1.69–1.83), and mesoscutum with anterior margin punctate. They are most
similar to male L. bruneri and L. reticulatum which both have anterior margin of mesoscutum rugose and clypeal hairs
Range. Nova Scotia west to British Columbia, Washington, south to Georgia and Colorado. USA: CO, CT, GA, IA,
ID, IL, IN, KY, MA, MD, ME, MI, MN, MO, NC, NH, NJ, NY, PA, UT, VA, VT, WI, WV. CANADA: AB, BC, ON,
NB, NS, PE, PQ.
DNA Barcode. Available. Multiple haplotypes.
Lasioglossum cressonii is known to nest in rotten wood (Mitchell 1960).
DNA barcodes of L. cressonii show levels of genetic divergence suggestive of multiple species (J. Gibbs unpublished
data). Morphological examination has not corroborated the existence of additional species. Additional study is
required before any new species in this possible complex can be described.
The specimen indicated above is designated herein as the lectotype to ensure stability in the application of the name.
A specimen of L. achilleae also occurs in the syntype series, which could potentially lead to confusion.