Lasioglossum (Dialictus) eremum sp. nov. urn:lsid:zoobank.org:act: 76F04F95-0D86-42FF-A596-C7415D9BB1FF Figs 21–23, 94B Diagnosis Females of L. eremum sp. nov. have the tegula relatively small (exceeding posterior margin of mesoscutum in dorsal view by about a seta’s breadth if at all), with inner posterior margin straight or very weakly concave, and usually moderately sparsely punctate laterally at midlength (IS = 1–2 PD); metapostnotum rugose due to very strong anastomosing rugae reaching posterior margin; postgena smooth, at most weakly lineolate; mesoscutum and mesepisternum mostly shiny (mesoscutum becoming tessellate anteromedially and mesepisternum sometimes dull dorsally); T1 anterior slope coriarious; and apical rims of T1–T2 distinctly punctate with punctation similar to discs (sometimes slightly sparser). Females of L. eremum sp. nov. are most similar to those of L. diabolicum sp. nov., L. ellisiae, L. gaudiale, and L. helianthi. Females of L. diabolicum and L. ellisiae have the postgena lineate and apical rims of T1–T2 impunctate or with minute, sparse, obscure punctures. Females of L. gaudiale have the tegula inner posterior margin more strongly concave and often more densely punctate laterally at midlength (IS 3 PD) and absent on rim; T2 disc shiny, with punctures dense (IS ≤1 PD), becoming moderately sparse near premarginal line (IS = 1–3 PD), apical rim shiny, with punctures absent. STRUCTURE. Face length/width ratio 0.84 (± 0.02 SD); gena/eye width ratio 0.8 (±0.05 SD). Pronotal angle obtuse; intertegular span 0.74 (± 0.01 SD) mm; mesoscutum length/width ratio 0.95 (± 0.06 SD); mesoscutum/scutellum length ratio 2.61 (± 0.27 SD); scutellum/metanotum length ratio 1.74 (±0.02 SD); metanotum/metapostnotum length ratio 0.82 (± 0.14 SD); forewing with 3 submarginal cells; tegula enlarged, reaching posterior margin of mesoscutum; inner posterior margin weakly concave; tegula length 0.43 (± 0.01 SD) mm, width 0.22 (± 0.01 SD) mm; propodeum lateral carinae not reaching dorsal margin; oblique carina absent. (n = 2) GENITALIA. Not examined. VARIATION. The one other male specimen examined has the mandible completely dark, scutellum entirely densely punctate (IS <1 PD), and both forewings with only two submarginal cells. Range Mountains from Nevada to New Mexico and north to Wyoming (Fig. 23). Floral hosts APOCYNACEAE: Apocynum L.: A. androsaemifolium L. • ASTERACEAE: Chrysothamnus • Heterotheca: H. subaxillaris • EUPHORBIACEAE: Euphorbia: E. albomarginata Torr. & A.Gray • FABACEAE: Melilotus: M. officinalis • PAPAVERACEAE: Argemone. DNA barcodes Two confirmed sequences available (BOLD process IDs: DLII1060-07, DLIII183-19). There is a small amount of divergence within these sequences (0.16% maximum intraspecific p-distance). They are closest in terms of p-distance to L. ellisiae (2.68% minimum interspecific p-distance). Six fixed nucleotide substitutions distinguish L. eremum sp. nov. from all other Nearctic species of the L. gemmatum complex: 15(C), 63(C), 75(G), 162(C), 199(A), and 573(A) (Supp. file 2). Comments Rare. Lasioglossum eremum sp. nov. is evidently restricted to rugged, relatively high elevation terrain. It is not found in flat plains or deserts except for a single specimen from Carrizozo, New Mexico, collected by Raymond Beamer among a very long series of L. coactus. It is possible that this specimen is mislabeled and actually belongs to the long series of L. eremum from Carrizo Creek, Arizona, which were collected one week later by Lucy Beamer. Alternatively, the mountains or extremely rugged lava fields near Carrizozo may be suitable habitat for this species.

Published as part of Gardner, Joel & Gibbs, Jason, 2023, Revision of the Nearctic species of the Lasioglossum (Dialictus) gemmatum species complex (Hymenoptera: Halictidae), pp. 1-222 in European Journal of Taxonomy 858 (1) on pages 70-76, DOI: 10.5852/ejt.2023.858.2041, http://zenodo.org/record/7629347