Lasioglossum (Dialictus) cephalotes (Dalla Torre)

Gibbs, Jason, 2011, Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini), Zootaxa 3073, pp. 1-216 : 67-70

Lasioglossum (Dialictus) cephalotes (Dalla Torre)

( Figures 77–78 )

Halictus cephalicus Robertson, 1892: 270 . Ƥ 3. (junior primary homonym of Halictus cephalicus Morawitz, 1873 ) Lectotype. Ƥ USA, Illinois, Macoupin Co., Carlinville, 21.vii.1891, (C. Robertson); [INHS]. by W. E. LaBerge (inWebb 1980). 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 Ƥ3, p. 447 (redescription, key); Krombein, 1967: Lasioglossum (Paralictus) cephalotes , p. 467 (catalogue); Hurd, 1979: Paralictus cephalotes , p. 1974 (catalogue); Moure & Hurd, 1987: Paralictus cephalotes , p. 143 (catalogue).

Diagnosis. Female L. cephalotes can be recognised by the following diagnostic combination: head massive (head width = 2.02 mm), mandible large nearly reaching opposing mandible base, preapical tooth absent, gena much wider than eye, pronotal ridge carinate, mesepisternum punctate, and metapostnotum smooth with short rugae limited to base. They are similar to L. lionotum , L. rozeni and L. platyparium . Female L. rozeni and L. platyparium both have the metapostnotum extensively rugose. Female L. lionotum are much smaller (head width = 1.13–1.20 mm).

Male L. cephalotes can be recognised by the following diagnostic combination: head wide and large (length/width ratio = 0.91; head width 1.54 mm), gena and postgena lineolate, antennal sockets widely separated (IAD/OAD> 1.9), pronotal ridge carinate, and mesepisternum punctate. They are most similar to L. lionotum and L. wheeleri . Male L. lionotum are much smaller (head width 1.15–1.22 mm) and have gena and postgena relatively polished. Male L. wheeleri have a less modified head and postgena imbricate.

Redescription. FEMALE. Length 6.05–6.23 mm; head length 1.50–1.68 mm; head width 1.80–2.02 mm; forewing length 4.48–4.60 mm

Colouration. Head and mesosoma very dull metallic bluish green. Antenna dark brown, flagellum with ventral surface reddish brown. Tegula dark amber. Wing membrane faintly dusky, venation and stigma amber. Legs brown, except tibial bases and apices, and medio- and distitarsi amber, basitarsi suffused with amber. Metasoma brown, terga and sterna with apical margins translucent brownish yellow.

Pubescence. Dull white. Sparse throughout. 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 appressed hairs. Pronotal collar with dense tomentum. Propodeum with moderately dense 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 curving above ventral surface. Penicillus greatly reduced, indistinguishable from other hairs. Metasomal terga with moderately sparse, fine hairs but no apparent tomentum. T1 acarinarial fan absent, medial portion of declivitous surface without erect hairs. T3–T4 without evident fringes. Sternal hairs erect, posteriorly directed (2–3 OD).

Surface sculpture. Face polished, weakly imbricate, punctation fine. Clypeus an supraclypeal area punctation obscured in holotype. Lower paraocular and antennocular areas with punctation moderately sparse (i=1–2d). Upper paraocular area and frons punctation contiguous (i≤d). Ocellocular area punctate (i=1–1.5). Gena polished. Postgena imbricate. Mesoscutum polished, punctation sparse between parapsidal lines (i=1–2d), relatively dense laterad of parapsidal line (i=0.5–1.5d) and dense on anterolateral portion (i≤d). Mesoscutellum similar to mesoscutum. Axilla punctate. Metanotum rugulose-imbricate. Preëpisternum rugulose. Hypoepimeral area imbricate-punctate. Mesepisternum polished, finely punctate (i=1–1.5d). Metepisternum dorsal half rugulose, ventral half imbricate. Metapostnotum with longitudinal rugae not reaching 1/3 distance to posterior margin, posterior surface weakly imbricate. Propodeum with dorsolateral slope weakly imbricate, lateral and posterior surfaces tessellate. Metasomal terga polished except apical impressed areas faintly coriarious, punctation fine (i=1–1.5d), apical impressed areas impunctate.

Structure. Head enormous, very wide (length/width ratio = 0.83). Eyes subparallel (UOD/LOD ratio = 1.00–1.04). Labrum enlarged and flattened without distinct basal tubercle, apical process without dorsal keel. Mandibles large, scythe-like, with minute subapical angle. Clypeus 1/3 below suborbital tangent, apicolateral margins widely convergent. Antennal sockets distant (IAD/OAD> 0.75). Frontal line carinate, ending 2.5 OD below median ocellus. IOD less than OOD. Gena huge, nearly 1.5 times as wide as eye. Hypostomal carinae divergent towards mandible bases. Pronotal dorsolateral angle acute. Pronotal ridge carinate, weakly interrupted by sulcus. Basitibial plate with posterior carina weak. Inner metatibial spur pectinate with 4 short branches. Metapostnotum truncate (MMR ratio = 1.32), posterior margin rounded onto posterior surface. Propodeum with oblique carina fine, 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 4.38 mm; head length 1.39 mm; head width 1.54 mm; forewing length 3.87 mm.

Colouration. Head and mesosoma dull green with bluish reflections. Flagellum with ventral surface brownish orange. Tegula orange. Wing venation and pterostigma yellowish brown. Legs brown, tibial base and tarsi yellow.

Pubescence. Face with subappressed tomentum obscuring lower paraocular area and partially obscuring clypeus. S3–S4 with apicolateral tufts.

Surface sculpture. Clypeus and supraclypeal area with sparse punctation (i=1–2d). Frons with dense but distinct punctation (i≤d). Gena and postgena lineolate. Hypoepimeral area and mesepisternum polished, distinctly punctate. Metapostnotum with coarse rugae nearly reaching posterior margin. Propodeum with dorsolateral slope rugose.

Structure. Head wide (length/width ratio = 0.91). Eyes strongly convergent below (UOD/LOD ratio = 1.33). Clypeus 1/2 below suborbital line, apicolateral margins convergent. Antennal sockets very distant (IAD/OAD> 1.9). Frontal line carinate, ending 2 OD below median ocellus. Hypostomal carinae only slightly divergent towards mandibles. Pedicel subequal to F1. F2 length 2.0X F1. F2–F10 moderately elongate (length/width ratio = 1.53– 1.67). Metapostnotum truncate (MMR ratio = 1.55), posterior margin rounded onto posterior surface.

Terminalia . Not examined.

Range. New York west to Iowa ( Fig. 74 ). USA: IA, IL, NY.

Additional specimens examined. USA: ILLINOIS: 13 paratype, Carlinville, (C. Robertson); [ INHS]; IOWA: 13 Sioux City, 21.ix.1923 (C.N. Ainslie); [2 submarginal cells in left wing, metasoma missing]; 1Ƥ Sioux City, 21.ix.1923 (C.N. Ainslie) [head missing]; 1Ƥ Sioux City, clay bank,? 20.ix.1918? (C.N. Ainslie), [stylopized, pinned with male L. zephyrum ]; [ AMNH]; NEW YORK: Suffolk Co., N41.0371 W071.9248, 7.ix.2005 (S.W. Droege); [ PCYU].

DNA barcode. Available. Partial sequence.

Comments. Uncommon.

Lasioglossum cephalotes is the type species of 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) reports L. imitatum (as L. inconspicuum ) as a host of L cephalotes but this was likely a misidentification of L. lionotum . Morphological and molecular comparison show close affinities to L. lionotum (Gibbs et al. in press.). Lasioglossum lionotum is a social parasite of L. imitatum and closely related to both L. imitatum and L. zephyrum ( Danforth et al. 2003; Gibbs et al. in press.).

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. lionotum .

Gibbs (2010b) misidentified an undescribed species ( L. rozeni below) for L. cephalotes . The holotype of L. cephalotes was recently re-examined and the mistake was realized.

Figures

FIGURE 74. Distribution map of Lasioglossum batya (stars), L. ceanothi (circles) and L. cephalotes (squares).

FIGURE 77. Lasioglossum cephalotes (Dalla Torre) female, (A) lateral habitus, (B) face. Scale bars = 1 mm.

FIGURE 78. Lasioglossum cephalotes (Dalla Torre) male, (A) lateral habitus, (B) face. Scale bars = 1 mm.