Lasioglossum (Dialictus) asteris (Mitchell)

Gibbs, Jason, 2010, Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini) 2591, Zootaxa 2591 (1), pp. 1-382 : 69-73

Lasioglossum (Dialictus) asteris (Mitchell)

( Figures 73A–C , 74A–E )

Paralictus asteris Mitchell, 1960: 446 . ♀ ♂. Holotype. ♀ USA, North Carolina, Cliffs of the Neuse State Park , Wayne Co., 21.x.1955 [Mitchell].

Taxonomy. Krombein, 1967: Lasioglossum (Paralictus) asteris , p. 467 (catalogue); Hurd, 1979: Paralictus asteris , p. 1974 (catalogue); Moure & Hurd, 1987: Paralictus asteris , p. 142 (catalogue).

Diagnosis. Females of L. asteris , L. cephalotes , L. michiganense , L. platyparium and L. sitocleptum are recognisable by the characters typical of social parasites such as the lack of scopa, enlarged head, scythe-like mandible, acute pronotal dorsolateral angle ( Fig. 5B ) and flattened labrum without dorsal keel ( Fig. 3B ). Female L. asteris may be differentiated from other parasitic species by their small size (4.0– 4.6 mm), mandible without subapical tooth or angle, gena much broader than eye and imbricate metapostnotum. Other parasitic species are larger (5.0–6.0 mm) and have typically rugoso-striate metapostnotum. Female L. cephalotes have very narrow mandibles without a subapical tooth or angle, a flattened basal tubercle on the labrum and weakly divergent hypostomal carinae. Female L. michiganense have a distinct subapical tooth, gena width subequal to eye and vertical striations on the mesepisternum. Female L. platyparium and L. sitocleptum both have a distinct basal tubercle on the labrum and a very weak subapical angle on the mandible. These final two can be distinguished by the much broader gena of L. platyparium (1.5 times eye width) relative to L. sitocleptum (subequal to eye width)

Males of L. asteris , L. cephalotes , L. packeri , L. platyparium and the eastern USA species L. wheeleri (Mitchell) are recognisable by the acute pronotal dorsolateral angle. Male L. asteris may be differentiated from other parasitic species by their small size (4.2–4.5 mm), very wide separation of the antennal sockets (IAD/OAD> 2.0), strong pronotal collar and sometimes vein 1rs-m incomplete or absent. Male L. cephalotes have dense tomentum on the lower paraocular area which obscures the surface below and have a strong pronotal collar. Male L. packeri have abundant facial tomentum and very distinct mesepisternal punctures. Male L. platyparium have a relatively weak pronotal collar which is not noticeably different from non-parasites. Male L. wheeleri have very distinct mesepisternal punctures.

Redescription. FEMALE. Length 4.15–4.64 mm; head length, 1.13–1.20 mm; head width 1.25–1.30 mm; forewing length 2.99–3.23 mm.

Colouration. Head and mesosoma dull greenish blue, nearly brown. Labrum yellowish brown. Mandible orange. Pronotal lobe yellowish brown. Legs brown, tibial bases and apices, and tarsi yellowish brown. Antenna dark brown, flagellum with ventral surface reddish-brown. Tegula translucent yellow. Wing membrane subhyaline, venation and pterostigma pale honey-coloured. Metasoma dark brown, terga and sterna with apical margins translucent brownish yellow.

Pubescence. Dull white. Very sparse. Head and mesosoma with moderately sparse woolly hairs (1–1.5 OD), longest on genal beard, metanotum and mesopleuron (1.5–2.5 OD). Face without appressed hairs. Pronotal collar with dense tomentum. Propodeum with sparse plumose hairs on lateral and posterior surfaces (1.5–2 OD). Mesofemoral comb reduced to sparse row of hairs. Mesotibial comb similarly reduced to cluster of dense hairs. Metafemoral scopa reduced relative to nest-building species. Penicillus greatly reduced, indistinguishable from other setae. Metasomal terga with sparse, fine setae. T1 acarinarial fan absent. Metasomal terga without appressed tomentum, sterna with posterior directed simple hairs (2–3 OD).

Surface sculpture. Face polished, weakly imbricate, punctation extremely fine. Clypeal punctation sparse (i=1–3d), except on basal margin (i=d). Supraclypeal area with punctation sparse (i=2–3d). Lower paraocular and antennocular areas with punctation moderately sparse (i=1–1.5d). Upper paraocular area and frons punctation distinctly separated (i=d). Ocellocular area minutely punctate (i=1–2d). Gena polished. Postgena imbricate. Mesoscutum polished, punctation fine, sparse between parapsidal lines (i=2–4d), laterad of parapsidal line (i=2d), and on anterolateral portion (i=1–2d). Mesoscutellum polished, submedial punctation obscure (i=2–3d). Axilla punctate. Metanotum polished. Preëpisternum, hypoepimeral area, and mesepisternum weakly imbricate, punctation sparse (i=2–3d). Metepisternum with dorsal half weakly ruguloso-striate, ventral half imbricate. Metapostnotum imbricate with at most weak basal striations. Propodeum with dorsolateral slope and lateral and posterior surfaces weakly imbricate-tessellate. Metasomal terga faintly coriarious, punctation fine, uniformly spaced on disc (i=1–1.5d), apical impressed area virtually impunctate.

Structure. Head enormous, very wide (length/width ratio = 0.90–0.93, head to mesosoma width ratio = 1.6). Eyes weakly divergent below to subparallel (UOD/LOD ratio = 0.95–0.99). Labrum enlarged and flattened, apical process without dorsal keel, basal tubercle broad and flat. Mandibles large, scythe-like, subapical tooth absent. Clypeus 1/5 below suborbital tangent, apicolateral margins very strongly convergent. Antennal sockets moderately distant (IAD/OAD <0.9). Frontal line carinate, ending 3 OD below median ocellus. IOD less than OOD. Median ocellus above upper ocular tangent. Gena very broad, maximum width nearly twice as wide as eye at midpoint. Pronotal dorsolateral angle acute. Pronotal ridge sharply angled, complete, not interrupted by sulcus. Mesoscutum with anteromedial margin broadly rounded, overhanging pronotum. Basitibial plate reduced and lower carina absent. Inner metatibial spur pectinate with 2–3 short teeth. Metapostnotum truncate (MMR ratio = 1.56–1.64), posterior margin broadly rounded onto posterior surface. Propodeum with oblique carina very weak, lateral carina very short. T5 medial specialized area reduced in size relative to nonparasitic females.

MALE. Similar to female except for the usual secondary sexual characters and as follows. Length 4.20– 4.45 mm; head length 1.18–1.27 mm; head width 1.15–1.22 mm; forewing length 3.05–3.17 mm;

Colouration. Labrum brown. Flagellum with ventral surface brownish yellow to orange-yellow. Tibial bases and apices orange-yellow.

Pubescence. Sparse. Lower paraocular area with sparse, subappressed hairs not obscuring surface. S2–S5 lateral portions with weak hair tufts (1–1.5 OD).

Surface sculpture. Facial punctation coarse. Metapostnotum longitudinally striate.

Structure. Head moderately elongate (length/width ratio = 1.00–1.04). Eyes convergent below (UOD/ LOD ratio = 1.31–1.32). Clypeus 1/2 below suborbital tangent, apicolateral margins strongly convergent. Subantennal sutures strongly incurved. Antennal sockets very distant (IAD/OAD = 2.0). Frontal line carinate, ending 2 OD below median ocellus. IOD subequal to OOD. Pedicel subequal to F1. F2 length 1.6–1.7X F1. F2–F10 moderately short (length/width ratio = 1.18–1.44). Gena narrower than eye. Pronotum dorsolateral angles orthogonal. Metapostnotum truncate (MMR ratio = 1.44–1.64), posterior margin weakly angled onto posterior surface.

Terminalia . S7 with median lobe large, broadly acuminate, apex flat ( Fig. 74D ). S8 with apicomedial margin weakly convex ( Fig. 74D ). Genitalia as shown in Fig. 74D–E . Gonobase with ventral arms thick, not evidently separated. Gonostylus small with erect setae, dorsal setae elongate. Retrorse lobe wide, attenuated apically.

Range. Ontario south to Alabama, west to Kansas ( Fig. 75 ).

Additional material examined. CANADA: ONTARIO: 1♂ Forks of Credit , 9.vii.1968 (P. MacKay) ; 1♀ Oliver Bog , 3k. S Salt, 26.ix–11.x.1987 (D. Blades) ; 1♂; [ PCYU] ; USA: ALABAMA: 1♀ Clay Co., Clairmont Springs Rd at Idaho Rd , UTM 0595690 3687303, 31.v.2007 (J. Hanula, S. Horn, M. Ulyshen); DIS- TRICT OF COLUMBIA : 1♀ Washington, Sidwell School , 12.x.2007 ; MARYLAND: 1♀ Fairfax Co., 4.viii.2008 (D. Crombline) ; 1♂ Prince George’s Co., N38.9623 W076.7464, 22.ix.2006 (K. Hutson); MIS- SOURI : 1♀ Wayne Co., Williamsville , 1–20.ix.1988 (J. T. Becker) ; NORTH CAROLINA: 1♂ S of Bryson City, Bryson City & Queen Branch Rds. , N35.28377 W083.4872, 8.viii.2006 (J. Gibbs) ; VIRGINIA: 5♂♂ Arlington , 4.viii.2008 (D. Crombline); [ PCYU] ; WEST VIRGINIA: 1♀ paratype Hardy Co., Lost River S.P., 29.vii–11.viii.1957 (K. V. Krombein); [ NMNH] .

Floral records. ASTERACEAE : Aster , FABACEAE : Melilotus , Robinia .

Biology. Mitchell, 1960: (predator); Michener 1978: (host); Wcislo 1997: (biology, host); Danforth 1999: (phylogeny); Danforth & Ji 2001: (phylogeny); Danforth et al. 2003: (phylogeny).

Comments. Uncommon. Vein 1rs-m is often incomplete or absent. The host species, L. imitatum , has a much more extensive range (see below).

Figures

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

FIGURE 5. Gena of female Dialictus (A) narrower than eye, (B) wider than eye.

FIGURE 73. Lasioglossum asteris (Mitchell). Female (A) lateral habitus; (B) dorsal habitus; (C) face. Scale bars, A–C = 1 mm.

FIGURE 74. Lasioglossum asteris (Mitchell). 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 75. Distribution of Lasioglossum asteris (dark grey) and L. atwoodi (light grey).