Lasioglossum (Dialictus) cressonii (Robertson)

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 101-106

Lasioglossum (Dialictus) cressonii (Robertson)

( Figures 92A–F , 93A–F )

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<d). Gena and postgena coarsely strigate. Mesoscutum weakly imbricate, punctation coarse, moderately dense between parapsidal lines (i=1–1.5d), dense laterad of parapsidal lines (i<d) and reticulate on anterolateral portion. Mesoscutellum similar to mesoscutum, submedial punctation moderately sparse (i=1=1–2.5d). Axilla reticulate. Metanotum rugose. Preëpisternum, hypoepimeral area and mesepisternum strongly rugose. Metepisternum with dorsal two-thirds rugoso-striate. Metapostnotum rugoso-striate. Propodeum entirely strongly rugose. Metasomal terga polished except apical halves faintly coriarious, punctation on basal halves moderately dense (i=1.5–2d), sparse on apical halves (i=3–5d).

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 areas impunctate.

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, reflexed apically.

Range. Nova Scotia west to British Columbia, south to Georgia and Colorado ( Fig. 94 ).

Additional material examined. CANADA: ALBERTA: 1♀ Edmonton , 30.viii.1984 (Thormin, Spanton & Nicholson); [ PMAE] ; BRITISH COLUMBIA: 5♀ Richmond , N49°08´41´´ W123°04´24´´ m 4.vi.2003 (C. Ratti) ; ONTARIO: 1♀ Joker’s Hill , N44.039 W079.531, 17.vi.2006 (J. Gibbs) ; 17♀ Manester Tract, St. Williams , N42°43´W080°26´, 15–22.vi.1992 (L. Packer) ; 5♀ 4♂♂ Manester Tract, St. Williams , N42°43´W080°26´, 22.vii.1995 (L. Packer) ; NEW BRUNSWICK: 1♀ Kent Co., St. Ignace , N46.707 W071.054, 31.vii.2005 (M. Gravel) ; NOVA SCOTIA: 1♀ Annapol. Co., Middleton , N44.9665 W065.5755, 13.ix.2001 (C. Sheffield) ; 1♀ 1♂ Cape Breton I., Baddeck , 29.viii.1985 (L. Packer) ; 1♀ Kings Co., Pereau , N45.2046 W064.3786, 24.vi.2003 (Sheffield, Rigby & Jansen); [ PCYU] ; QUEBEC: 1♀ Laval Univ. , 26.vi–2.vii.1971; [ PMAE] ; USA: COLORADO: 1♀ Jefferson Co., N39.731 W105.244, 21.viii.2001 (S.W. Droege) ; 1♀ Larimer Co., N40.6833 W105.3975, 11–12.v.2004 (S.W. Droege); [ PCYU] ; GEORGIA: 1♀ Putnam Co., Oconee N.F., 11.iv.2008 (J. Hanula & S. Horn); [ PCYU] ; INDIANA: 1♀ Jasper Co., Prairie Border , 1.vii.2003 ( R. P. Jean) ; 1♀ Vigo Co., Landsbaum , 13.iv.2001 ( R. P. Jean) ; MAINE: 2♀ Hancock Co., N44.3608 W068.23, 20.vi. (H.W. Ikerd) ; MARYLAND: 1♀ Garrett Co., N39.566 W079.428, 7.[?].2004 (S.W. Droege); MASSA- CHUSETTS: 1♀ Middlesex Co., sandpit, 1.1 mi SE of Pepperell , 11.vi.2006 (M.F. Veit) ; MICHIGAN: 1♂ Allegan Co., N42.5538 W086.0437, 28.viii.2003 (S.W. Droege) ; MINNESOTA: 3♀ Minnetonka, U of Minnesota Arboretum , vi.2005 (L. Packer) ; MISSOURI: 1♀ Dallas Co., Lead Mine CA , 2.v.2001 (Arduser); 2♀ Marion Co., Elmslie Forest Nat. Area , 6 mi. N Monroe City, 16–18.iv.2004 (Arduser) ; NEW HAMPSHIRE: 1♀ Coos Co., Cherry Ponds NWR , Jefferson , 26.vi.2006 (M.F. Veit) ; NEW YORK: 3♀ Hwy 63, N of Genesio, N42.8235 W077.7425, 11.vi.2006 (J. Gibbs); [ PCYU] ; 1♀ Orange Co., Cornwall, Black Rock Forest , 18- N4585216 E582593, 15.viii.2003 ( V. Giles & J. Rozen); [ AMNH] ; 6♀ Suffolk Co., 6.ix.2005 (S.W. Droege); [ PCYU] ; 1♀ Suffolk Co., Gardiners Island , 29.iv.2006 ( R.G. Goelet); [ AMNH]; NORTH CARO- LINA: 1♀ Blue Ridge Parkway, 10 km of Asheville , N35.663 W082.479, 4.vi.2005 (A. Zayed) ; 1♀ 1♂ Grandfather Mtn. , N36.08942 W081.83699, 13.viii.2006 (J. Gibbs) ; 2♀ N of Doughton Park , N36.44752 W081.02898, 14.viii.2006 (J. Gibbs) ; VERMONT: 1♀ Essex Co., Nulhegan NWR , Brighton , 2.vii.2006 (M.F. Veit); [ PCYU] .

Floral records. ACERACEAE : Acer , ALISMATACEAE : Alisma plantago-aquatica , ANACAR- DIACEAE: Rhus , APIACEAE : Chaerophyllum procumbens , Cryptotaenia canadensis , Daucus carota , APO- CYNACEAE: Apocynum androsaemifolium , AQUIFOLIACEAE : Ilex , ASTERACEAE : Achillea millefolium , Anaphalis , Arnoglossum reniforme , Cirsium , Erigeron annuus , E. philadelphicus , Eurybia macrophylla , Euthamia graminifolia , Heliomeris multiflora , Hieracium , Leucanthemum vulgare , Packera aurea , Solidago juncea , Symphyotrichum drummondii , S. leave , Taraxacum , BRASSICACEAE : Barbarea , Berteroa , Brassica , Capsella bursa-pastoris , CAPRIFOLIACEAE : Symphoricarpos orbiculatus , Viburnum prunifolium , V. dentatum , CELASTRACEAE : Euonymus , CORNACEAE : Cornus , ERICACEAE : Rhododendrom, Vaccinium , FABACEAE : Amorpha , Melilotus , Trifolium , GERANIACEAE : Geranium , GROSSULARI- ACEAE: Ribes , HYDRANGEACEAE : Hydrangea , Philadelphus , HYDROPHYLLACEAE : Hydrophyllum , Phacelia , LAMIACEAE : Salvia , LAURACEAE : Sassafras albidum , “ Smilacina ”, LILIACEAE : Allium canadense , Hypoxis hirsuta , Lilium philadelphicum , Maianthemum stellatum , Uvularia grandiflora , MAL- VACEAE: Althaea rosea , ONAGRACEAE : Epilobium , Ludwigia polycarpa , POLYGONACEAE : Fagopyrum , PORTULACEAE : Claytonia virginica , RANUNCULACEAE : Enemion biternatum , Pulsatilla patens ssp. multifida , Ranunculus abortivus , ROSACEAE : Amelanchier canadensis , Crataegus mollis , Fragaria ,

Malus sylvestris , Potentilla , Prunus serotina , Rubus , RUBIACEAE : Houstonia purpurea , RUTACEAE : Ptelea trifoliata , Zanthoxylum americanum , SALICACEAE : Salix amygdaloides , S. cordata , S. interior , SCRO- PHULARIACEAE: Pedicularis , Verbascum thapsus , VIOLACEAE : Viola cucullata .

Biology. Reinhard 1924: (possible predator, as D. cressoni ?); Evans & Lin, 1959: (predator); Evans, 1964: (predator); Sakagami & Michener, 1962, pp. 14: (nesting substrate); Danforth 1999: (phylogeny); Danforth & Ji 2001: (phylogeny); Danforth et al. 2003: (phylogeny).

Comments. Abundant. This is the type species for the genus-group name Chloralictus .

DNA barcoding reveals this species is represented by a group of sequences with deep divergences not evidently related to geography. Specimens collected at the same time and location may have different DNA barcode haplotypes. Morphological examination has failed to yield corresponding anatomical characters. Base substitutions between haplotypes were mostly in the third codon position, suggesting that only functional copies and no pseudogenes were amplified (Song et al. 2008). Two other possibilities for this pattern are heteroplasmy (e.g., Magnacca & Brown 2009), or cryptic speciation. Additional study is needed to determine what is the cause of the discrepancy. The barcodes do not give a pattern of paraphyly (i.e. no other species arise within the L. cressonii cluster), so identification should still be possible using this method.

Synonymy of L. delectatum is supported by morphological comparison including examination of male genitalia. The holotype of L. delectatum has the lower mesepisternum densely foveolate with punctures visible from certain angles rather than coarsely rugose throughout. This is believed to be merely a specimen of L. cressonii with unusual sculpturing rather than a separate species.

Figures

FIGURE 92. Lasioglossum cressonii (Robertson). Female (A) lateral habitus; (B) dorsal habitus; (C) face; (D) mesoscutum; (E) mesepisternum; (F) metapostnotum. Scale bars, A–C = 1 mm.

FIGURE 93. Lasioglossum cressonii (Robertson). Male (A) lateral habitus; (B) dorsal habitus; (C) face; (D) ventral view of genital capsule; (E) dorsal view of genital capsule; (F) S7, S8. Scale bars, A–C = 1 mm, F = 0.5 mm.

FIGURE 94. Distribution of Lasioglossum cressonii, (light grey) and L. dashwoodi (dark grey).