Lasioglossum (Dialictus) heterognathum (Mitchell)

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 136-140

Lasioglossum (Dialictus) heterognathum (Mitchell)

( Figures 114A–E , 115A–G )

Dialictus heterognathus Mitchell, 1960: 397 . ♀.

Holotype. ♀ USA, North Carolina, Grandfather Mt. , 27.vi.1952, [ NCSU]. Examined.

Dialictus banksi Mitchell, 1960: 434 . ♂.

Holotype. ♂ USA, North Carolina, West End , 14.vi.1950, (Mitchell); [ NCSU]. Examined.

Taxonomy. Knerer and Atwood, 1963: Dialictus heterognathus ♂, p. 167 (description); Knerer and Atwood, 1966: D. heterognathus , p. 882 (synonymy); Krombein, 1967: Lasioglossum (Dialictus) heterognathum , p. 463 (catalogue); Hurd, 1979: Dialictus heterognathus , p. 1966 (catalogue); Moure & Hurd, 1987: Dialictus heterognathus , p. 103 (catalogue).

Diagnosis. Females of L. heterognathum can be recognized by the diagnostic combination of a large and wide head (length/width ratio = 0.92–0.96), gena wider than eye ( Fig. 114D ), divergent hypostomal carinae ( Fig. 114E ) and fine mesoscutal punctures. They are most similar to L. imitatum and L. apocyni which both have parallel hypostomal carinae.

Males of L. heterognathum can be recognised by polished moderately dense facial tomentum limited to lower paraocular area, elongate flagellomeres (length/width ratio = 1.50–1.85), obtuse dorsolateral angles of the pronotum, mesoscutum dull due to weak microsculpture and sparse punctures on central disc (i=2–3d), distinct fine punctures on mesepisternum (i=1–3d), and apical impressed areas of the metasomal terga impunctate. They are most similar to the eastern USA species L. wheeleri which have acute dorsolateral angles of the pronotum.

Redescription. FEMALE. Length 4.64–6.19 mm; head length 1.08–1.63 mm; head width 1.18–1.68 mm; forewing length 3.23–3.97 mm.

Colouration. Head and mesosoma bluish green. Clypeus with apical 2/3 blackish brown and basal portion, and supraclypeal area with brassy reflections. Antenna dark brown, flagellum with ventral surface reddish brown to orange. Mesoscutum often with substantial green reflections. Tegula reddish amber. Wing membrane subhyaline, venation and pterostigma amber. Legs brown, medio- and distitarsi reddish brown. Metasoma blackish brown, terga and sterna with apical margins brown to brownish yellow.

Pubescence. Dull white. Sparse. Head and mesosoma with moderately sparse woolly hairs (1–1.5 OD), longest on genal beard, metanotum and mesopleuron (2–2.5 OD). Paraocular area with sparse subappressed hairs. Gena with sparse tomentum. Propodeum with moderately dense plumose hairs on lateral and posterior surfaces (2–2.5 OD). Metasomal terga with sparse, fine setae. T1 acarinarial fan with wide dorsal opening. T2–T3 basolaterally and T4–T5 entirely with sparse, scattered tomentum.

Surface sculpture. Face polished, faintly imbricate, punctation fine. Clypeus polished, punctation sparse (i=1–5d). Supraclypeal area with punctation sparse (i=2–3d). Lower paraocular and antennocular areas with punctation moderately sparse (i=1–2.5d). Upper paraocular area and frons with clearly separate punctures (i=1–1.5d). Ocellocular area minutely punctate. Gena polished. Postgena imbricate-lineolate. Mesoscutum polished, faintly imbricate, punctation fine, moderately sparse between parapsidal lines (i=2–3d), moderately dense laterad of parapsidal line (i=1–1.5d) and dense on anterolateral portion (i≤d). Mesoscutellum polished, medial line punctation distinctly separated (i=d). Axilla punctate. Metanotum imbricate. Preëpisternum and mesepisternum imbricate, rugulose above. Metepisternum with dorsal third weakly rugoso-striate, ventral portion imbricate. Metapostnotum incompletely, weakly striate. Propodeum with dorsolateral slope imbricate, lateral and posterior surfaces tessellate. Metasomal terga coriarious, punctation on basal halves sparse (i=1.5– 3d), apical half impunctate (except along premarginal line).

Structure. Head large and quadrate, wide (length/width ratio = 0.92–0.96), broader than mesosoma. Eyes weakly convergent below (UOD/LOD ratio = 1.05–1.14). Clypeus projecting 1/3–1/2 below suborbital line, apicolateral margins convergent. Antennal sockets close (IAD/OAD ratio <0.5). Frontal line carinate, ending>2 OD below median ocellus. OOD greater than IOD. Gena wider than eye. Hypostomal carinae divergent towards mandible bases. Inner metatibial spur pectinate with 3–4 teeth. Metapostnotum short (MMR ratio = 1.21–1.40), posterior margin broadly rounded onto posterior surface. Propodeum with oblique carina weak, lateral carina not reaching dorsal margin.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 4.70– 5.37 mm; head length 1.36–1.49 mm; head width 1.34–1.39 mm; forewing length 3.54–3.97 mm.

Colouration. Flagellum with ventral surface orange-yellow. Femoral-tibial joint and tarsi brownish yellow; protibia infused with brownish yellow.

Pubescence. Clypeus, supraclypeal area, and paraocular area with moderately dense tomentum largely obscuring surface. Frons with sparse tomentum not obscuring surface. Metasomal sterna sparsely pubescent.

Surface sculpture. Gena lineolate. Mesepisternum punctate (i=1–3d). Metapostnotum longitudinally striate, not reaching posterior margin. Propodeum with dorsolateral slope rugose. Metasomal terga more deeply punctate (i=2–3d), apical impressed margin impunctate.

Structure. Head elongate (length/width ratio = 0.99–1.07). Eyes strongly convergent below (UOD/LOD ratio = 1.57–1.64). Clypeus projecting 1/2 below suborbital line, apicolateral margins subparallel. Antennal sockets distant (IAD/OAD ratio> 1.5). Frontal line carinate, ending>2 OD below median ocellus. OOD greater than IOD. Gena narrower than eye. Postgena impressed adjacent to hypstome. Hypostomal carinae parallel. Pedicel subequal to F1. F2 length 2.0–2.2X F1. F2–F10 moderately elongate (length/width ratio = 1.50–1.85). Metapostnotum moderately elongate (MMR ratio = 1.33–1.40), posterior margin rounded onto posterior surface.

Terminalia . S7 with median lobe strongly clavate, apex rounded ( Fig. 115G ). S8 with apicomedial margin weakly convex ( Fig. 115G .). Genitalia as in Fig. 115D–F . Gonobase with ventral arms widely separated. Gonostylus small, dorsal setae elongate. Retrorse lobe narrow, attenuated apically.

Range. Nova Scotia to Ontario, west to Minnesota, and south to North Carolina ( Fig. 113 ).

Additional material examined. CANADA: NEW BRUNSWICK: 2♀ (paratypes) Charlotte Co., 13.viii.1956 (W. T. A. Neilson) ; 1♀ Fredericton , 25.v.1961 [ CNC] ; ONTARIO: 1♀ 1♂ Constance Bay , 13– 19.viii.1977 (M. Sanborne); [ PMAE] ; 2♀ Forks of Credit , 12.viii.1969 (P. MacKay) ; 2♀ 4♂♂ Forks of Credit , 21.viii.1969 (P. MacKay) ; 2♀ Forks of Credit , 29.viii.1969 (P. MacKay); [ ROM] ; 4♀ Madoc , 10.v.1962 (G. Knerer); [ ROM; PCYU] ; 1♀ Toronto, York University N43.77175 W079.4965, 20.iv.2006 (J. Gibbs); [ PCYU] ; QUEBEC: 2♀ Gatineau Pk., Mountian Rd. , 12.vii.1965 (P.S. Corbet); [ PMAE] ; USA: MAINE: 1♀ Acadia, Mt. Desert Camp , 21.vii.1978 (P.E. Hallet); [ PHPC] ; MICHIGAN: 1♀ Huron Co., Port Hope , 8.v.1965 (J. & L. Donahue); [ CUIC] ; MINNESOTA: 1♀ Minnetonka, U. of Minnesota Arboretum , vi.2005 (L. Packer) ; NEW HAMPSHIRE: 1♂, 22.viii.1960, on Solidago, R.A. Morse ; [ PCYU] ; NEW YORK: 1♂ Schuyler Co., Hector Land Use Area, nr Reynoldsville , 16.viii.1977 (G. & K. Eickwort); [ CUIC] ; NORTH CAROLINA: 1♀ Great Smoky Mountain N.P., Cataloochee overlook, N35.63997 W083.06017, 6.viii.2006 (C. Sheffield); [ GSNP] ; WEST VIRGINIA: 1♀ Hampshire Co., N38.4049 W078.5153, 7.vii.2002 (S.W. Droege) ; 1♀ Hampshire Co., N38.4376 W078.6083, 7.vii.2002 (S.W. Droege) ; 1♀ Hampshire Co., N38.415 W078.5012, 7.vii.2002 (S.W. Droege) ; 1♀ Hampshire Co., N39.2325 W078.5174, 29–30.v.2005 (S.W. Droege); [ PCYU] ; WISCONSIN: 15♀ Dane Co., Indian Lk. , 24.vii.1996 ( R. A. Henderson); [ IRCW]..

Floral records. ANACARDIACEAE : Rhus , APIACEAE : Daucus carota , APOCYNACEAE : Apocynum androsaemifolium , ARALIACEAE : Aralia , ASTERACEAE : Doellingeria umbellata , Solidago , Symphyotrichum lateriflorus , Taraxacum officinale , BRASSICACEAE : Barbarea vulgaris , CAPRIFOLIACEAE : Viburnum , FABACEAE : Melilotus alba , HYDRANGEACEAE : Deutzia gracilis , Hydrangea , ROSACEAE : Malus , Rubus .

Comments. Common. Females of L. heterognathum exhibit large variation in head size and shape which are presumably related to caste differentiation with allometry.

Figures

FIGURE 113. Distribution of Lasioglossum foveolatum (dark grey), L. heterognathum (light grey), and L. hudsoniellum (medium grey).

FIGURE 114. Lasioglossum heterognathum (Mitchell). Female (A) lateral habitus; (B) dorsal habitus; (C) face; (D) lateral view of head; (E) hypostomal carina. Scale bars, A–C = 1 mm.

FIGURE 115. Lasioglossum heterognathum (Mitchell). Male (A) lateral habitus; (B) dorsal habitus; (C) face; (D) ventral view of genital capsule; (E) dorsal view of genital capsule; (F) apical view of genital capsule; (G) S7, S8. Scale bars, A–C = 1 mm, G = 0.5 mm.