Lasioglossum (Dialictus) eremum, Gardner & Gibbs, 2023

Gardner, Joel & Gibbs, Jason, 2023, Revision of the Nearctic species of the Lasioglossum (Dialictus) gemmatum species complex (Hymenoptera: Halictidae), European Journal of Taxonomy 858 (1), pp. 1-222 : 70-76

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 <1 PD); T1 anterior slope very shiny; metapostnotum rugae usually not reaching posterior margin; and postgena sometimes lineate. Females of L. helianthi have the mesoscutum entirely tessellate and postgena lineate.

Males of L. eremum sp. nov. have the tegula relatively small (reaching but not exceeding posterior margin of mesoscutum in dorsal view), with inner posterior margin weakly concave, and entirely covered in deep, crowded punctures (IS = 0 PD) except with some narrow interspaces <1 PD laterally at midlength; metapostnotum rugose and propodeum lateral surface extensively rugulose due to very strong anastomosing rugae reaching posterior margin; face with sparse tomentum restricted to paraocular area; mesepisternum with crowded punctures (IS = 0 PD); and metasomal terga with depressed apical rims impunctate.

Males of L. eremum sp. nov. are most similar to those of L. holzenthali sp. nov. and members of the L. stictaspis species complex. Males of L. holzenthali have the clypeus and supraclypeal area with sparse tomentum; tegula more sparsely punctate with more distinct interspaces (IS ≥0.5 PD); metapostnotum with subparallel rugae and propodeum lateral surface smooth and shiny; and metasomal terga with depressed apical rims punctate. Males in the L. stictaspis species complex have the face uniformly covered in dense tomentum below the eye emargination and mesepisternum usually more sparsely punctate with distinct interspaces (IS ≥ 0.5 PD).

Etymology

The specific epithet ʻ eremum ʼ is the Latinized Greek adjective ʻ eremos ʼ (lonely). It refers to the fact that this species is primarily known from singleton specimens in remote locations.

Material examined

Holotype UNITED STATES – Utah • ♀; Washington Co., 0.63 mi. NNW of Lemmon Spring ; 37.2953° N, 112.9092° W; 16 Jun. 2006; F. Nicklen, B. Hays leg.; ex Apocynum androsaemifolium ; BBSL ZION23556 .

[Verbatim label: USA UT Washington Co. / 0.63 mi NNW Lemmon Spr. 12S E330774 N4129346 16Jun06 / F.Nicklen, B.Hays / Apocynum androsaemifolium / ZION 23556 // 2388C04 // HOLOTYPE / Lasioglossum (Dialictus) eremum Gardner and Gibbs ]

Paratypes

UNITED STATES – Arizona • 1 ♀; Coconino Co.; 35.35393° N, 111.73061° W; 19 Jun. 2012; Dave Smith leg.; NAUF4 A 0087470 • 3 ♀♀; Carrizo Creek ; [33.9° N, 110.28° W]; 16 Jun. 1950; R. H. Beamer leg.; SEMC • 34 ♀♀; ibid.; 16 Jun. 1950; R. H. Beamer leg.; ex Euphorbia albomarginata ; SEMC • 1 ♂; Chiricahua Mountains, Southwestern Research Station ; [31.883° N, 109.205° W]; elev. 1646 m; 19 Aug. 1964; Charles D. Michener leg.; ex Heterotheca subaxillaris ; SEMC • 1 ♀; Flagstaff ; [35.2° N, 111.65° W]; 14 Jul. 1947; L.D. Beamer leg.; SEMC • 1 ♀, 1 ♂; Huachuca ; [31.5° N, 110.4° W]; 1937; W. Benedict leg.; SEMC • 1 ♀; Santa Rita Mountains ; [31.7° N, 110.8° W]; elev. 1524–2438 m; July; F.H. Snow leg.; SEMC. – Nevada • 1 ♀; Clark Co., Lovell Canyon ; 36.1648° N, 115.5758° W; 20 May 2005; E. Ahlstrom leg.; BBSL640067 • 1 ♀; Ely ; [39.25° N, 114.87° W]; 30 Jun. 1950; C.D. Michener leg.; ex Melilotus officinalis ; SEMC . – New Mexico • 1 ♀; Socorro Co., Cibola NF: South Baldy meadow ( MG2 ); 33.9911° N, 107.1837° W; elev. 3178 m; 16 Jun. 2017; J.A. Fowler leg.; BBSL1070450 • 1 ♀; Carrizozo ; [33.64° N, 105.88° W]; 9 Jun. 1950; L.D. Beamer leg.; SEMC . – Utah • 2 ♀♀; Beaver Co., Milford ( UT 21 , mi. 60); [38.434° N, 113.289° W]; 3 Jun. 1994; G. Bryant leg.; ex Argemone ; BBSL FaunalSurvey No. 000 085 362, FaunalSurvey No. 000 085 363 • 1 ♀; Washington Co., Central ; [37.42° N, 113.62° W]; 19 Sep. 1956; Knowlton and Goodarzi leg.; ex Chrysothamnus sp. ; SEMC . – Wyoming • 1 ♀; Platte Co., Warm Spring, Camp Guernsey ; [42.26° N, 104.76° W]; elev. 1372 m; 6 Jun. 2000; P.M. Pineda, J. Schmidt leg.; CSUC .

Description

Female

COLOURATION. Head and mesosoma blue to olive green; clypeus apex black; labrum reddish brown; mandible orange with black base and red apex; flagellum dark reddish brown dorsally, light brown ventrally. Pronotal lobe reddish brown; legs dark reddish brown; tegula black to reddish brown; wing membrane hyaline, veins with subcosta dark brown, otherwise light brown. Metasoma black with rims of terga and sterna broadly translucent brown.

PUBESCENCE. Body pile colour white. Tomentum dense on gena anteriorly, pronotal collar and lobe, space between pronotal lobe and tegula, metanotum anteriorly, T2–T3 basolaterally, and T4 througout; sparse on paraocular area and metepisternum. Mesoscutum pubescence thin to moderately plumose. Wing setae dark, short and dense. Acarinarial fan complete, dense. T2 fringes dense, T3 fringes dense.

SURFACE SCULPTURE. Clypeus shiny, with punctures dense in basal fourth (IS ≤1 PD), large and irregularly sparse apically (IS <2 PD); supraclypeal area shiny, with punctures dense (IS ≤1 PD); paraocular area shiny, with punctures dense (IS <1 PD), sparser around antenna socket (IS ≤ 1 PD); frons shiny, with punctures dense (IS <1 PD); vertex shiny, with punctures dense laterally (IS <1 PD), fine and sparse medially (IS = 1–3 PD); gena shiny, with punctures fine, moderately dense (IS = 1–2 PD); postgena shiny, becoming lineolate posteriorly. Tegula punctures fine, sparse (IS = 1–3 PD); mesoscutum shiny, becoming weakly tessellate anteromedially, with punctures moderately dense (IS = 1–2 PD), becoming dense on lateral and posterior margins (IS <1 PD); scutellum shiny, with punctures dense (IS <1 PD); metapostnotum weakly tessellate, with rugae strong, anastomosing, reaching posterior margin; preëpisternum shiny with crowded punctures (IS = 0 PD); hypoepimeron shiny, with punctures crowded (IS = 0 PD); mesepisternum shiny, with punctures dense (IS <1 PD); metepisternum weakly rugulose; propodeum lateral surface tessellate, posterior surface tessellate. T1 anterior slope weakly coriarious, disc shiny, with punctures moderately dense (IS = 1–2 PD), becoming fine and moderately sparse on rim (IS = 1–3 PD) and absent in small subapicolateral boss; T2 disc shiny, with punctures moderately dense (IS = 1–2 PD), apical rim shiny, with punctures fine, moderately sparse (IS = 1–3 PD).

STRUCTURE. Face length/width ratio 0.8 (± 0.01 SD); clypeus apicolateral denticles rounded acute points; gena/eye width ratio 0.96 (± 0.06 SD). Pronotal angle obtuse; intertegular span 0.85 (± 0.07 SD) mm; mesoscutum length/width ratio 0.88 (± 0.03 SD); mesoscutum/scutellum length ratio 2.88 (± 0.17 SD); scutellum/metanotum length ratio 1.6 (± 0.2 SD); metanotum/metapostnotum length ratio 0.75 (±0.11 SD); forewing with 3 submarginal cells; tegula enlarged, reaching posterior margin of mesoscutum; inner margin concave; tegula length 0.42 (± 0.03 SD) mm, width 0.21 (± 0.01 SD) mm; propodeum lateral carinae not reaching dorsal margin; oblique carina strong, straight. T2 depressed apical rim less than 50% of tergum. (n = 9)

VARIATION. The tegula punctures can vary from dense (IS ≤ 1 PD) to sparse (IS = 1–3 PD), the inner posterior margin can be straight or weakly concave, the T1–T2 apical rim punctures can vary from moderately dense (IS = 1–2 PD) to sparse (IS = 1–3 PD), and the supraclypeal area is sometimes black or brassy.

Male

COLOURATION. Head and mesosoma blue to blue-green; clypeus apex black; labrum black; mandible orange with black base and red apex; flagellum black dorsally, light brown ventrally. Pronotal lobe dark brown; legs brown; tegula dark reddish brown; wing membrane hyaline, veins with subcosta dark brown, otherwise brown to light brown. Metasoma black with depressed apical rims of terga and sterna and downcurved lateral areas of terga translucent brown.

PUBESCENCE. Body pile colour white. Tomentum dense on pronotal collar; sparse on paraocular area and gena. Mesoscutum pubescence simple to sparsely plumose. Wing setae dark, short and sparse. Sterna pubescence moderately short (1–2 OD), sparsely plumose, sparse.

SURFACE SCULPTURE. Clypeus shiny, with punctures dense (IS <1 PD); supraclypeal area shiny, with punctures dense (IS <1 PD); paraocular area shiny, with punctures dense (IS <1 PD); frons shiny, with punctures crowded (IS = 0 PD); vertex shiny, with punctures dense laterally (IS <1 PD), moderately dense medially (IS = 1–2 PD); gena shiny, with punctures fine, moderately sparse (IS = 1–2 PD); postgena lineate. Tegula punctures crowded (IS = 0 PD); mesoscutum shiny, becoming weakly tessellate anteromedially, with punctures dense (IS ≤ 1 PD), becoming sparse anteromedially (IS = 1–3 PD); scutellum shiny, with punctures dense (IS <1 PD), becoming sparser medially (IS = 1–2 PD); metanotum shiny and finely, densely punctate (IS <1 PD); metapostnotum shiny, with rugae strong, anastomosing, reaching posterior margin; preëpisternum areolate; hypoepimeron shiny, with punctures crowded (IS = 0 PD); mesepisternum shiny, with punctures crowded (IS = 0 PD); metepisternum rugulose; propodeum lateral surface rugulose, becoming smooth and imbricate medially, with punctures crowded (IS = 0 PD), becoming slightly sparser medially (IS <1 PD), posterior surface shiny with crowded punctures (IS = 0 PD). T1 anterior slope shiny, disc shiny, with punctures sparse (IS = 1–3 PD), becoming very sparse in large subapicolateral boss (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.

Figures

Fig. 21. Lasioglossum (D.) eremum sp. nov., ♀ (BBSL1070450). A. Dorsal habitus. B. Lateral habitus. C. Face. D. Metasoma and propodeum. Scale bars = 1 mm.

Fig. 22. Lasioglossum (D.) eremum sp. nov., ♂ (SEMC). A. Dorsal habitus. B. Lateral habitus. C. Face. D. Metasoma and propodeum. Scale bars = 1 mm.

Fig. 23. Georeferenced collection records of Lasioglossum (D.) eremum sp. nov. (black squares) and predicted distribution by maximum entropy ecological niche modelling in Maxent (colour shading). Warmer colours indicate higher cloglog probability of occurrence.

Fig. 94. Scutellum and metapostnotum. A. Lasioglossum gaudiale (Sandhouse, 1924), ♀, scutellum coarsely punctate and metapostnotum rugae not reaching posterior margin. B. L. eremum sp. nov., ♀, scutellum finely punctate and metapostnotum rugae reaching posterior margin. Scale bars = 0.5 mm.