Lasioglossum (Dialictus) cephalotes (Dalla Torre)

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 93-96

Lasioglossum (Dialictus) cephalotes (Dalla Torre)

( Figures 87A–C , 88A–E )

Halictus cephalicus Robertson, 1892: 270 . ♀ ♂. (Preocc. Morawitz, 1873)

Lectotype. ♀ USA, Illinois, Carlinville, 15.vii., (C. Robertson); [INHS: 179,606] by W.E. LaBerge. Examined. Halictus cephalotes Dalla Torre, 1896: 57 . (new name for H. cephalicus Robertson )

Taxonomy. Robertson, 1901: Paralictus cephalicus , p. 229 (generic description); Viereck, 1916: Halictus (Paralictus) cephalicus , p. 706 (key); Michener, 1951: Lasioglossum (Paralictus) cephalotes , p. 1119 (catalogue); Mitchell, 1960: Paralictus cephalotes , p. 447 (redescription); Krombein, 1967: Lasioglossum (Paralictus) cephalotes , p. 467 (catalogue); Hurd, 1979: Paralictus cephalotes , p. 1974 (catalogue); Moure & Hurd, 1987: Paralictus cephalotes , p. 143 (catalogue).

Diagnosis. See diagnosis for L. asteris .

Redescription. FEMALE. Length 4.76–4.88 mm; head length 1.44–1.73 mm; head width 1.82–1.85 mm; forewing length 3.90–4.03 mm.

Colouration. Head and mesosoma very dull metallic greenish blue, nearly brown. Clypeus with apical 2/3 blackish brown. Antenna dark brown, flagellum with ventral surface reddish. Tegula pale translucent amber. Wing membrane subhyaline, venation and pterostigma amber. Legs brown, tarsi reddish to brownish yellow. Metasoma reddish brown, terga and sterna with apical margins pale translucent 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). Face without tomentum. Frons and upper paraocular area with moderately dense setae, most apparent when viewed from below. Pronotal collar without dense tomentum. Propodeum with sparse plumose hairs on lateral and posterior surfaces (2–2.5 OD). Mesofemoral and mesotibial combs dense but short relative to non-parasitic species. Metafemoral scopa reduced relative to nest-building species, only a few elongate hairs curved onto ventral surface. Penicillus reduced to a few thick bristles. Metasomal terga with moderately sparse, fine setae. T1 acarinarial fan visible only as a few appressed lateral hairs. T2–T3 basolaterally and T4 entirely with scattered tomentum. T3–T4 with moderately dense elongate setae. Sternal hairs, subappressed, not arranged as scopa (2–3 OD).

Surface sculpture. Face weakly imbricate, punctation extremely fine. Clypeus polished, punctation sparse (i=1–3d). Supraclypeal area with punctation sparse (i=1–6d). Lower paraocular and antennocular areas with punctation moderately dense (i=1–1.5d). Upper paraocular area and frons punctation dense (i<d). Ocellocular area punctation dense (i=d). Gena and postgena strigate. Mesoscutum polished, punctation fine, sparse between parapsidal lines (i=1.5–4d), moderately dense laterad of parapsidal lines (i=1–1.5d) and dense on anterolateral portion (i≤d). Mesoscutellum similar to mesoscutum, punctation sparse (i=1–3d). Axilla punctate. Metanotum weakly imbricate. Preëpisternum and hypoepimeral area imbricate. Mesepisternum dorsal half weakly rugulose, ventral half imbricate. Metepisternum with dorsal two-fifths weakly striate, ventral portion imbricate. Metapostnotum irregularly striate. Propodeum with dorsolateral slope imbricate, lateral and posterior surfaces tessellate. Metasomal terga polished except apical impressed areas weakly coriarious, punctation uniformly close (i=1–1.5d), except apical impressed area nearly impunctate.

Structure. Head enormous, very wide (length/width ratio = 0.78–0.82). Eyes subparallel (UOD/LOD ratio = 1.00–1.02). Labrum enlarged and flattened without distinct basal tubercle, apical process flat and wide without dorsal keel ( Fig. 3B ). Mandible large, scythe-like, without subapical tooth, very narrow, tapering evenly to apex reaching to opposing mandibular base. Clypeus 1/5 below suborbital line, apicolateral margins convergent. Antennal sockets distant (IAD/OAD = 0.8). Frontal line carinate, ending>2 OD below median ocellus. IOD less than OOD. Median ocellus at upper ocular tangent. Gena huge, one and half times as wide as eye. Hypostomal carinae divergent towards mandible. Pronotal dorsolateral angle acute ( Fig. 6B ). Pronotal ridge angled, uninterrupted. and protrochanter unmodified. Basitibial plate lower carinae absent. Inner metatibial spur pectinate with 3–4 short teeth. Metapostnotum truncate (MMR ratio = 1.41–1.50), posterior margin weakly angled onto posterior surface. Propodeum with oblique carina very weak, lateral carina short, not reaching dorsal margin. T5 medial specialized area reduced in size relative to non-parasitic species.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 5.80 mm; head length 1.38–1.58 mm; head width 1.49–1.70 mm; forewing length 4.03 mm.

Colouration. Flagellum with ventral surface reddish brown. Tegula translucent brownish yellow. Tibial bases and apices, and tarsi brownish yellow.

Pubescence. Face with sparse tomentum. Lower paraocular area with dense tomentum obscuring surface. Gena without tomentum. S2–S5 apicolateral portions with sparse plumose hairs (1 OD).

Surface sculpture. Clypeus uniformly punctate (i=1–1.5d). Supraclypeal area with punctation sparse (i=1– 3d). Metanotum rugose. Metapostnotum completely rugoso-striate. Propodeum with dorsolateral slope rugose. Metasomal terga polished, punctation uniform (i=1.5–2d) except apical impressed areas impunctate.

Structure. Head wide (length/width ratio = 0.93). Eyes convergent below (UOD/LOD ratio = 1.27–1.34). Clypeus 1/2 below suborbital tangent, apicolateral margins subparallel. Antennal sockets distant (IAD/OAD> 1.7). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Pedicel shorter than F1. F2 length 1.7–1.8X F1. F2–F10 moderately elongate (length/width ratio = 1.43–1.55). Hypostomal carinae weakly divergent. Metapostnotum moderately elongate (MMR ratio = 1.29–1.35), posterior margin weakly angled onto posterior surface.

Terminalia . S7 with medial lobe wide, acuminate, apex rounded. S8 with apicomedial margin strongly convex. Genitalia as in Fig. 88D–E . Gonobase with ventral arms thick, widely separated. Gonostylus small, dorsal setae elongate. Retrorse lobe elongate, weakly attenuated, reflexed apically.

Range. Ontario south to North Carolina, west to Mississippi and Minnesota ( Fig. 89 ).

Additional material examined. USA: MARYLAND: 1♂ Pr. George’s Co., N39.0352 W076.8739, 21.vii.2004 (S. Kolski) ; 1♀ Pr. George’s Co., N39.0568 W076.8143, 2–3.x.2002 (E.J. Jackson) ; 5♀ Talbot Co., N38.8 W.076.2833, 7–8.v.2005 (W. Steiner) ; MASSACHUSETTS: 1♂ Worcester Co., sand pit, 1.6 mi SW of Lake Denison , 1.ix.2006 (M.F. Veit); [ PCYU] ; NEW YORK: 4♂♂ Suffolk Co., Gardiners I., 19.viii.2007 ( R. G. Goelet); [ AMNH] ; WEST VIRGINIA: 1♀ Hampshire Co., Capon Bridge, Buffalo Gap Camp , 20.vii.2001 (S. Droege); [ PCYU] .

Floral records. ASCLEPIADACEAE : Cynanchum leave , ASTERACEAE : Cirsium , Leucanthemum , Solidago , CORNACEAE : Cornus , SALICACEAE : Salix nigra .

Biology. Robertson, 1901: (possible host); Robertson, 1926: (possible host); Michener, 1978: (possible host).

Comments. Uncommon. This is the type species for the genus-group Paralictus .

Lasioglossum cephalotes has been collected at banks with nesting L. zephyrum ( Robertson 1901, 1926) and is presumably a social parasite on that species. Krombein (1967) erroneously reports L. imitatum (as L. inconspicuum ) as a host of L cephalotes . The range of L. zephyrum greatly exceeds the known range of L. cephalotes (see L. zephyrum below).

Ontario records for L. cephalotes reported by MacKay and Knerer (1979) are in fact L. asteris . No Canadian specimens of L. cephalotes have been examined but is retained in the revision for two reasons. The presence of L. cephalotes in adjacent states has been confirmed. Secondly, its presumed host species, L. zephyrum , is widespread in Canada. It seems probable that L. cephalotes occurs at least in Southern Ontario.

Figures

FIGURE 3. Labrum of female Dialictus; (A) nest-building species, (B) parasitic species. Arrows indicate apical process.

FIGURE 6. Dorsolateral angle of pronotum (A) obtuse, (B) acute.

FIGURE 87. Lasioglossum cephalotes (Dalla Torre). Female (A) lateral habitus; (B) dorsal habitus; (C) face. Scale bars, A–C = 1 mm.

FIGURE 88. Lasioglossum cephalotes (Dalla Torre). Male (A) lateral habitus; (B) dorsal habitus; (C) face; (D) ventral view of genital capsule, S7, S8; (E) dorsal view of genital capsule. Scale bars, A–C = 1 mm, E = 0.5 mm.

FIGURE 89. Distribution of Lasioglossum cephalotes (dark grey) and L. coeruleum (light grey).