Lasioglossum (Dialictus) stictaspis ( Sandhouse, 1923 )

Gardner, Joel & Gibbs, Jason, 2022, New and little-known Canadian LasIOGLOssum (DIaLICTus) (Hymenoptera: Halictidae) and an emended key to species, The Canadian Entomologist (e 3) 154 (1), pp. 1-37 : 24-28

Lasioglossum (Dialictus) stictaspis ( Sandhouse, 1923)

Figures 13 , 14 , 17A

Dialictus stictaspis Sandhouse 1923: 195 (holotype, ♂, deposited in USNM, examined)

Halictus (Chloralictus) albuquerquensis Michener 1937: 316 (holotype, ♀, deposited in CAS, examined) new synonymy

Lasioglossum (Dialictus) stictaspis – Michener 1951: 1119 (catalogue)

Lasioglossum (Chloralictus) albuquerquense – Michener 1951: 1112 (catalogue)

Dialictus stictaspis – Hurd 1979: 1971 (catalogue) – Moure and Hurd 1987: 131 (catalogue)

Dialictus albuquerquensis – Hurd 1979: 1964 (catalogue) – Moure and Hurd 1987: 89 (catalogue)

Specimens examined

Holotype: UNITED STATES – New Mexico ♂; Mesilla; [32.27° N, 106.8° W]; June year and day unknown; Cockerell leg.; USNM

Other material. (See Supplementary material, Table S1 for complete data including coordinates and collection codes.)

CANADA – Alberta 9♀; PMAE – Saskatchewan 1♂; CNC .

UNITED STATES – Colorado 4♀; CUIC 12♀, 1♂; SEMC 18♀, 4♂; UCMC – New Mexico 5♀; BBSL 1♀; CAS 1♀; NMSU 16♀, 9♂; SEMC 9♀; TAMU 3♀; UCMC – Texas 7♀, 1♂; BBSL 1♂ ; UCDC – Wyoming 1♀ ; UMSP.

Diagnosis. Females of L. stictaspis can be recognised by the combination of tegula enlarged (reaching posterior margin of mesoscutum in dorsal view), with inner posterior margin concave, and densely punctate in centre (IS ≤ 1 PD), metapostnotum dull due to tessellate microsculpture and usually with weak subparallel rugae, mesepisternum shiny (sometimes with weak microsculpture) and densely punctate (IS <1 PD), mesoscutum coarsely punctate (2–4 punctures between posterior end of parapsidal line and lateral edge of mesoscutum), T3 with dense subapical band of tomentum, and tegula and metasoma black to dark brown. They are most similar to L. ellisiae and several undescribed species from the southwestern United States of America and Mexico. Females of L. ellisiae have the metapostnotum shiny with strong, often anastomosing rugae, mesoscutum usually densely punctate (4–5 punctures between posterior end of parapsidal line and lateral edge of mesoscutum), tegula often more sparsely punctate (IS ≤ 2 PD), T3 usually without subapical tomentum, and tegula and/or metasoma sometimes orange.

Males of L. stictaspis can be recognised by the tegula densely punctate (IS ≤ 1 PD), relatively large (slightly exceeding posterior margin of mesoscutum in dorsal view), and inner posterior margin concave, with a small rounded projection posteriorly, mesoscutum relatively sparsely punctate (IS ≤ 1 PD near parapsidal line), mesepisternum densely punctate (IS <1 PD), metapostnotum dull due to tessellate microsculpture and usually with weak subparallel rugae, and T1–T3 with dense punctures reaching premarginal line (IS ≤ 1 PD). They are most similar to L. tegulare , L. ellisiae , and L. helianthi . All of these species have the tegula slightly smaller (not exceeding posterior margin of mesoscutum in dorsal view), inner posterior margin more weakly concave, coming to a narrow point or blunt angle posteriorly, and usually more sparsely punctate in part (IS ≥ 1 PD). Males of L. tegulare and L. ellisiae have the metapostnotum shiny with stronger parallel rugae. Males of L. ellisiae and L. helianthi have the mesoscutum slightly more densely punctate (IS <1 PD and IS <0.5 PD near parapsidal line, respectively) and tegula often slightly more sparsely punctate (IS ≤ 1 PD). Males of L. ellisiae also have T1–T3 with punctures becoming sparser towards the premarginal line.

Some other species (described and undescribed) from the southwestern United States of America and Mexico are also similar but do not occur sympatrically except in southern New Mexico, United States of America and, in one case, as far north as Colorado, United States of America, and will lack one or more of the diagnostic characters given above. These species will be revised in a forthcoming work.

Range. Western Great Plains and mountain valleys from New Mexico, United States of America to Alberta, Canada ( Fig. 17A ).

Floral hosts. Polylectic (Supplementary material, Table S2).

DNA barcodes. Three sequences available (BOLD process IDs: DLIII224-20, DLIII225-20, DLIII227-20). These sequences are very similar and poorly distinguished from three other undescribed species (maximum intraspecific P -distance 0.3%; minimum interspecific P -distance 0.64%).

Comments. The name Lasioglossum stictaspis has not been widely applied in the past because the primary diagnostic characters used for this species were the enlarged, punctate tegula and the presence of only two submarginal cells in the forewing ( Sandhouse 1923). The number of submarginal cells is known to be variable in many bees including several L. ( Dialictus ) species ( Gardner and Gibbs 2020; Scarpulla 2018), although this variation is typically rare. Among the specimens reported here, only one additional male from Las Cruces, New Mexico, United States of America was discovered with two submarginal cells. All other specimens have the usual three submarginal cells.

Many other species with an enlarged, punctate tegula can also have only two submarginal cells in rare cases, including L. gaudiale (Sandhouse, 1924) (new combination, see comments on L. tegulariforme below) and several undescribed species. In addition, the holotype of L. stictaspis is missing the head, limiting the number of visible alternative characters. As a result, the few specimens determined as L. stictaspis prior to this work are likely misidentified.

The female of L. stictaspis was associated by a series of both sexes from the same collecting event in Las Cruces, New Mexico, United States of America (very near the type locality), and a series of both sexes from Boulder County, Colorado, United States of America, from which DNA barcodes were obtained. The female was found to match the holotype of L. albuquerquense . This holotype is missing the metasoma, but an additional series of females in good condition from the type locality of Albuquerque, New Mexico, United States of America helped confirm the synonymy.

Figures

Fig. 13. Lasioglossum stictaspis (Sandhouse, 1923) (♀): A, lateral habitus; B, dorsal habitus; C, face; and D, propodeum and metasoma. Scale bars: 1 mm.

Fig. 14. Lasioglossum stictaspis (Sandhouse, 1923) (♂; A–B, D–F: holotype): A, dorsal habitus; B, lateral habitus; C, face; D, propodeum and metasoma; E, genital capsule (dorsal view with gonostylus parallel to plane of vision); and F, retrorse lobe (lateral view parallel to plane of vision). Scale bars: A–D, 1 mm; E–F, 0.25 mm.

Fig. 17. Georeferenced collection records (black squares) and predicted distribution by maximum entropy ecological niche modelling in Maxent (colour shading). Warmer colours indicate higher cloglog probability of occurrence. A, Lasioglossum stictaspis; and B, L. tegulariforme. Duplicate records within 0.1 degree were pruned to reduce bias.