Identification Summary: Moderately sized to large; thorax blue; has pits on mesepisturnum but often difficult to see; has no appressed hair on abdomen, but the long hairs on the abdomen are more abundant than normal and tan in color often giving the impression of something slightly hairy, in contrast with L. oblongum whose abdomen is almost completely absent of hairs of any kind; T1 hair fan is open at the top but not extremely widely open; pits on scutum are widely separated in the center but also between the nautalices and the tegula.
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 mm.; head and thorax green, abdomen piceous, legs rather uniformly dark; pubescence short, thin, entirely pale, apical abdominal terga quite fully exposed; length and breadth of head subequal; clypeus projecting about two-thirds below suborbital line; supraclypeal area considerably shorter than clypeus; eyes somewhat convergent below; lateral ocelli somewhat nearer eyes than to each other; cheeks subequal to eyes in width; upper portion of face densely and finely punctate, punctures around and below antennae well separated but not sparse, those on supraclypeal area somewhat finer but distributed about as facial areas on each side, clypeus very finely punctate along narrow upper margin, but becoming coarsely and quite sparsely punctate toward apical margin, apical half blackened; vertex and cheeks somewhat shining, punctures minute and hardly evident, cheeks becoming somewhat smoother below on each side of hypostomal carinae which are parallel, with the apical angle rather broadly rounded; scutum and scutellum somewhat shining, punctures very fine, well separated over most of scutum, even between notaulices and tegulae, scutellum with an impressed median line which is somewhat more finely and densely punctate, sparsely so on each side; pleura smooth, somewhat shining, with scattered and very fine and irregular punctures evident at certain angles; dorsal area of propodeum rather finely striate, completely so on each side, but median striations more irregular and not quite attaining the rounded apical margin, lateral faces of propodeum smooth and somewhat shining; wings subhyaline, veins and stigma pale testaceous, 2nd submarginal cell nearly as long as 3rd, receiving 1st recurrent vein toward apex; tegulae yellowish-hyaline, with some darker inner blotches; legs dark, but tarsal segments to some degree reddened; abdominal terga smooth and shining, punctures exceedingly minute, hardly evident on basal tergum, but terga 2 and 3 with rather numerous, minute and rather close punctures across basal half, apical impressed areas quite shallow, smooth, impunctate, becoming very narrowly yellowish along rims, discal pubescence very thin, suberect, not obscuring the apical segments to any degree.
DISTRIBUTION—Minnesota to New York, south to Georgia; April to September.
FLOWER RECORDS—Aquilegia, Aruncus, Barbarea, Fagopyrum and Robinia. Robertson (1929) records obscurus on the following: Arabia, Aster, Boltonia, Chaerophyllum, Circaea, Coreopsis, Cornus, Ellisia, Galium, Gnaphalium, Hellopair, Ilysanthes, Isopyrum, Osmorrhiza, Polemonium, Ranunculus, Smilacina, Stellaria and Symphoricarpus.
Retrieved from: Gibbs, J. 2010. Revision of the metallic species of Lasioglossum (Dialictus)in Canada (Hymenoptera, Halictidae, Halictini). Zootaxa; 2591, 215-220
Halictus obscurus Robertson 1892: 270. ♀.
Lectotype. ♀ USA, Illinois, Apr. 28-May 12 [INHS: 179,613] by W.E. LaBerge.. Examined.
Dialictus orbitatus Mitchell, 1960: 440. ♂. [new synonymy]
Holotype. ♂ USA, North Carolina, Bluff Park, Scenic Hgwy., [Doughton Park, Blue Ridge Pkwy], 24.vi.1948 (T.B.
Mitchell); [NCSU]. Examined.
Taxonomy. Robertson, 1902: Chloralictus obscurus, p. 249 (key); Viereck 1916: Halictus (Chloralictus)
obscurus, p. 707 (key); Michener, 1951: Lasioglossum (Chloralictus) obscurum, p. 1115 (catalogue); Mitchell,
1960: Dialictus obscurus ♀, p. 376 (redescription); Krombein, 1967: Lasioglossum (Dialictus) obscurum,
p. 465, L. (D.) orbitatum, p. 465 (catalogue); Hurd, 1979: Dialictus obscurum, p. 1969, D. orbitatus, p. 1969
(catalogue); Moure & Hurd, 1987: Dialictus obscurus, p. 117, D. orbitatus, p. 118 (catalogue).
Diagnosis. Females of L. obscurum can be recognised by the diagnostic combination of mesoscutal punctures
sparse including the lateral portions (Fig. 158D), mesepisternal punctures distinct, propodeal carinae
weak (Fig. 158E) 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 the metasomal terga. Female L. tenax have dense punctures on the lateral portions of the
Males of L. obscurum can be recognised by the moderately elongate head (length/width ratio = 1.02–
1.05), elongate flagellomeres (length/width ratio = 1.50–1.92), imbricate postgena, polished mesoscutum due
to weak microsculpture with sparse fine punctures on central disc (i=1–4d), punctate mesepisternum, apical
impressed areas of the metasomal terga impunctate, and sparse plumose hairs on the apicolateral portions of
S3–S5. They are similar to L. nigroviride, L. cattellae, L subversans, L. nevadense and L. tenax. Males of L.
nigroviride, L. nevadense, L. knereri and L. subversans have distinctly dense plumose hairs on the metasomal
sterna. Lasioglossum nevadense and L. knereri are not known to occur within the range of L. obscurum. 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) and have strong mesoscutal and
mesepisternal punctures, distinctly lineolate postgena, and moderately sparse hairs on the metasomal sterna.
Redescription. FEMALE. Length 4.88–5.86 mm; head length 1.44–1.58 mm; head width 1.49–1.66 mm;
forewing length 3.78–4.70 mm.
Colouration. Head and mesosoma golden green to bluish green. Clypeus with apical half blackish brown
and basal half, and supraclypeal area bronze. Antenna dark brown, flagellum with ventral surface brownish
yellow. Tegula reddish brown to pale amber. Wing membrane sometimes dusky, venation and pterostigma
amber. Legs brown, tarsi reddish brown. Metasoma dark brown, terga and sterna with apical margins translucent
Pubescence. Dull white. Very sparse. Head and mesosoma with moderately sparse woolly hairs (1–1.5
OD), longest on genal beard, metanotum and mesopleuron (2–2.5 OD). Lower paraocular area and gena without
subappressed tomentum. Propodeum with moderately dense plumose hairs on lateral and posterior surfaces (2–2.5 OD). Metasomal terga with sparse, fine setae. T2–T4 basolaterally with very sparse tomentum.
T2 apicolateral and T3–T4 apical margins with very sparse fringes.
Surface sculpture. Face imbricate, punctation fine. Clypeus polished, punctation moderately sparse (i=1–
3d). Supraclypeal area with punctation irregularly spaced (i=1–3d). Lower paraocular area punctation dense
(i≤d). Antennocular area punctation moderately dense (i=1–1.5d). Upper paraocular area and frons punctatereticulate.
Ocellocular area punctate (i≤d). Gena lineolate. Postgena imbricate. Mesoscutum imbricate, submedial
portion polished, punctation fine, moderately sparse between parapsidal lines (i=1–4d) and laterad of
parapsidal lines (i=1–2d), dense on anterolateral portions (i≤d). Mesoscutellum polished, submedial punctation
sparse (i=2–5d). Axilla punctate. Metanotum imbricate. Preëpisternum rugulose. Hypoepimeral area
imbricate-punctate (i=1–1.5d). Mesepisternum imbricate, weakly polished, distinctly punctate (i≤d), more
widely spaced on ventral portion (i=1–3d). Metepisternum with dorsal third rugoso-striate, ventral portion
imbricate. Metapostnotum incompletely longitudinally striate, posterior margin imbricate. Propodeum with
dorsolateral slope and lateral and posterior surfaces imbricate. Metasomal terga coriarious. T1 dorsal surface
obscurely, sparsely punctate. T2–T4 punctation on basal halves close (i=1–2d), apical half obscurely punctate
(except along premarginal line).
Structure. Head wide (length/width ratio = 0.95–0.97). Eyes convergent below (UOD/LOD ratio = 1.18–
1.20). Clypeus 2/3 below suborbital tangent, apicolateral margins convergent. Antennal sockets close (IAD/
OAD < 0.5). Frontal line carinate, ending 2 OD below median ocellus. Gena narrower than eye. Inner metatibial
spur pectinate with 3–4 teeth. Metapostnotum truncate (MMR ratio = 1.21–1.40), posterior margin
weakly angled onto posterior surface. Propodeum with oblique carina obscure, lateral carina weak, not reaching
MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 5.43–
5.92 mm; head length 1.54–1.61 mm; head width 1.51–1.54 mm; forewing length 4.39–4.58 mm.
Colouration. Flagellum with ventral surface pale brownish yellow. Tegula reddish brown. Wing membrane
subhyaline, venation and pterostigma reddish brown to pale brownish yellow. Tarsi tan to brownish yellow.
Pubescence. Paraocular area with subappressed tomentum obscuring surface. Clypeus with scattered
tomentum not obscuring surface. S3 apical half and S4–S5 lateral portions with dense, erect plumose hairs (1–
Surface sculpture. Mesoscutum polished to imbricate, punctation denser laterad of parapsidal lines (i≤d).
Mesepisternum polished, weakly imbricate with distinct punctation (i=1–1.5d). Metapostnotum with coarse
rugae, apical margin rounded onto posterior surface. Propodeum with dorsolateral slope and posterior surface
of propodeum rugose, lateral surface rugulose. Metasomal terga polished except margins weakly coriarious.
T2–T4 punctation on basal portions moderately dense (i=1–2d), apical impressed areas impunctate.
Structure. Head elongate (length/width ratio = 1.02–1.05). Eyes strongly convergent below (UOD/LOD
ratio = 1.39–1.58). Antennal sockets distant (IAD/OAD > 1.4). Frontal line carinate, ending 2 OD below
median ocellus. Pedicel less than F1. F2 length 1.57–1.69X F1. F2–F10 elongate (length/width ratio = 1.50–
1.92). Metapostnotum moderately elongate (MMR ratio = 1.17–1.20), posterior margin sharply angled onto
Terminalia. S7 with median lobe columnar, apex rounded (Fig. 159D). S8 with apicomedial margin
weakly convex (Fig. 159D). Genitalia as in Fig. 159D–E. Gonobase with ventral arms widely separated.
Gonostylus small, dorsal setae elongate. Retrorse lobe narrow, weakly attenuated apically.
Range. Ontario, south to North Carolina, west to Wisconsin, Missouri (Fig. 160).
Additional material examined. CANADA: ONTARIO: 1♀ Pt. Pelee, 7.vi.1961 (G. Knerer); USA: ILLINOIS:
1♀ Fermilab, 8.viii.2003 (D. Huie); MARYLAND: 1♀ Anne Arundel Co., N39.02727 W076.6669,
24–25.vii.2003 (R. Jackowski); 1♀ Montgomery Co., N38.97 W077.1565, 24.vi.2006 (S.W. Droege);
[PCYU]; MICHIGAN: 1♀ Filmore Twp., 29.vii.2004 (J. Tuell); [ARC]; MISSOURI: 1♀ Linn Co., Pershing
S.P., Locust Crk., 12.vii.2000 (Arduser); NEW HAMPSHIRE: 1♂ Meredith, 26.viii.1960 (R.A. Morse);
[PCYU]; NEW YORK: 6♀♀ Wayne Co., Endress, Sodus Pt, 19.v.2009 (M.G. Park); [CUIC]; 1♀ Worchester
Co., Ossining, Clemmons Garden, 21.vii.2005 (E. Fetridge); [PCYU]; NORTH CAROLINA: 1♀ Great
Smoky Mountain N.P., Cataloochee, N35.62813 W083.09997, 6.viii.2006 (J. Gibbs); [GSNP]; PENNSYLVANIA:
1♀ Montgomery Co., MapleA, N40.194 W075.369, 7.vii.2004 (L. Kurtz); TENNESSEE: 1♀ HWY 321,
nr Gatlinburg, N35.75988 W083.3615, 8.viii.2006 (J. Gibbs); VERMONT: 1♂ Lamoille Co., 4.5 mi NE Hyde
Park, 28.vii.2006 (M.F. Veit); VIRGINIA: 1♀ Frederick Co., N39.1928 W078.4197, 27.v.2005 (S.W.
Droege); 1♀ KOA, 15 km N of Harrisonburg, N38.534 W078.704, 6.vi.2005 (A. Zayed); WEST VIRGINIA:1♀ Hampshire Co., N39.2479 W078.5267, 6–8.viii.2006 (Students); 1♀ Hampshire Co., N39.2489
W078.5256, 30.vii.2005 [PCYU].
Floral records. ANACARDIACEAE: Rhus, APIACEAE: Chaerophyllum procumbens, Osmorhiza longistylis,
ASTERACEAE: Boltonia asteroides, Coreopsis palmata, Heliopsis helianthoides, Pseudognaphalium
obtusifolium, Rudbeckia, Symphyotrichum pilosum pilosum, S. ericoides ericoides, BRASSICACEAE: Arabis
shortii, A. laevigata, Barbarea, CAPRIFOLIACEAE: Symphoricarpos orbiculatus, CARYOPHYLLACEAE:
Stellaria media, CORNACEAE: Cornus florida, FABACEAE: Melilotus, Robinia, HYDROPHYLLACEAE:
Ellisia nyctelea, Hydrophyllum, LAMIACEAE: Stachys, LILIACEAE: Maianthemum racemosum, M. stellatum,
ONAGRACEAE: Circaea lutetiana, POLEMONIACEAE: Polemonium reptans, POLYGONACEAE:
Fagopyrum, PORTULACACEAE: Claytonia virginica, RANUNCULACEAE: Aquilegia, Enemion biternatum,
Ranunculus recurvatus, R. hispidus nitidus, ROSACEAE: Aruncus, Prunus persica, Spiraea, RUBIACEAE:
Galium aparine, SCROPHULARIACEAE: Lindernia dubia.
Additional floral records for an Eastern Kansas species tentatively identified as this species are as follows.
ANACARDIACEAE: Rhus aromatica, R. glabra, ASTERACEAE: Echinacea purpurea, Rudbeckia, BRASSICACEAE:
Erysimum repandum, FABACEAE: Amorpha canescens, A. fruticosa, Dalea, Medicago sativa,
Melilotus officinalis, Robinia pseudoacacia, HIPPOCASTANACEAE: Aesculus glabra glabra, LAMIACEAE: Monarda fistulosa, M. f. fistulosa mollis, LILIACEAE: Camassia scilloides, RHAMNACEAE:
Ceanothus herbaceus, ROSACEAE: Crataegus, Fragaria virginiana, Malus pumila, Prunus serotina, Zizia
aurea, SALICACEAE: Salix.
Biology. Reinhard 1924: (predator); Evans & Lin, 1959: (predator); Michener, 1966: (life history, nest
architecture, floral relationships, as obscurus?).
Michener (1966) considered the species called L. obscurus? as very similar to L. versatum. These species
are easily separable which suggests that the species studied by Michener may not have been L. obscurum.
Extracted from Jason Gibbs. 2011. Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini.) Zootaxa.
Lasioglossum (Dialictus) obscurum (Robertson)
Halictus obscurus Robertson 1892: 270. ♀.
Lectotype. ♀ 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 ♀, 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 ♀♂, 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. 24A), 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.