Lasioglossum (Dialictus) imbriumbrae, Gardner & Gibbs, 2020

Gardner, Joel & Gibbs, Jason, 2020, The ‘ red-tailed’ Lasioglossum (Dialictus) (Hymenoptera: Halictidae) of the western Nearctic, European Journal of Taxonomy 725, pp. 1-242 : 100-105

Lasioglossum (Dialictus) imbriumbrae sp. nov.

urn:lsid:zoobank.org:act:FA28AC7F-5BB1-4AD7-9FDB-2C3506701720

Figs 43–45 , 108C , 115B

Diagnosis

Females of Lasioglossum imbriumbrae sp. nov. can be recognized by the head and mesepisternum shiny with large, dense (i <1 pd) but distinctly separated punctures (except on the frons medially), face short (length/width ratio ~0.8), and T2–4 with dark spiracular spots. They are most similar to L. mesillense . Females of L. mesillense have the frons with finer and slightly but distinctly separated punctures, and hypoepimeron and upper mesepisternum with slightly smaller and crowded, indistinct punctures (i=0 pd).

Males of L. imbriumbrae sp. nov. can be recognized by the propodeum smooth with very strong dull microsculpture, mesepisternum densely punctate (i <1 pd), T1–3 rims almost completely impunctate, wings lightly infuscated with dark veins and dark hairs, scutum and metasoma with somewhat densely plumose hair, and clypeus apical margin and labrum reddish brown. They are most similar to L. minckleyi sp. nov., L. mesillense , L. austerum sp. nov., and L. hudsoniellum . All of these species have T1–3 rims punctate. In addition, males of L. mesillense have the flagellomeres relatively long (F2 about 2 times as long as F1 and 1.6 times as long as broad), propodeum shiny, and clypeus apical margin and labrum usually orange. Males of L. austerum sp. nov. have the mesepisternum slightly more sparsely punctate (i ≤ 1 pd) and scutum and metasoma with mostly thin and weakly plumose hair. Males of L. hudsoniellum have S5 apical margin straight, mesosoma and metasoma with more extensive tomentum, and clypeus apical margin and labrum usually orange.

Etymology

The specific epithet imbriumbrae is formed from the Latin noun ‘ imber ’ (‘rain’) and the genitive singular noun ‘ umbrae ’ (‘shadow’). It refers to this species’ narrow distribution in the rain shadow of the Sierra Nevada Mountains. An appropriate translation would be the rain shadow sweat bee.

Material examined

Holotype

UNITED STATES – California • ♀; Olancha ; [36.28° N, 118.01° W]; 2 May 1927; Timberlake leg.; ex Salix exigua ; UCRC.

[Verbatim label: on Salix exigua // Olancha / Cal. May 2, 27 // Timberlake Coll. // HOLOTYPE / Lasioglossum (Dialictus) imbriumbrae Gardner and Gibbs ]

Paratypes

UNITED STATES – California • 1 ♀; Inyo Co., Bishop ; [37.36° N, 118.4° W]; 21 Jun. 1929; E.P. Van Duzee leg.; CAS • 1 ♀; Mono Co., Tom’s Place, Rock Creek ; [37.56° N, 118.68° W]; 1888 m a.s.l.; 6 Oct. 2002; E.F. Drake leg.; ex Chrysothamnus sp.; UCRC • 2 ♀♀; same collection data as for holotype; UCRC. – Nevada • 1 ♀, 1 ♂; Washoe Co., Pyramid Lake ; [40° N, 119.5° W]; 29 Jun. 1968; D.S. Horning Jr. leg.; UCDC • 1 ♀, 1 ♂; Carson City; [39.16° N, 119.77° W]; 12 Aug. 1940; L J. Lipovsky leg.; SEMC .

Description

Female

COLOURATION. Head and mesosoma blue to blue-green; clypeus apical colour black to reddish brown; labrum black, reddish brown, or orange; mandible orange with black basal band and red tip; flagellum black to reddish brown dorsally, reddish brown to orange ventrally; pronotal lobe black to reddish brown;

metasoma red to orange with dark spiracular spots on T2–4 (sometimes faint), sometimes dark on T1 and T3 laterally and T4–5 throughout; legs black to reddish brown with femur-tibia joints, base and apex of tibiae, and tarsi sometimes orange; tegula reddish brown; wing membrane lightly infuscated, veins with subcosta dark brown, otherwise pale amber to brown.

PUBESCENCE. Body hair colour white. Tomentum dense on gena, pronotal collar and lobe, space between pronotal lobe and tegula, T2 narrow basolateral patches, T3 narrow basal band, and T4 throughout; sparse on paraocular area and episterna. Scutum hair thin to moderately plumose. Wing hairs dark, short and dense. Acarinarial fan complete, very sparse. T2 fringes sparse, T3 fringes sparse.

SURFACE SCULPTURE. Clypeus punctures dense in basal third (i <1 pd), large and irregularly spaced apically (i <2 pd), sculpture shiny, sometimes weakly imbricate basally; supraclypeal area punctures dense (i ≤ 1 pd), sometimes sparse medially (i= 1–3 pd), sculpture shiny or weakly imbricate; paraocular area punctures dense (i <1 pd), irregularly sparser around antenna socket (i <2 pd), sculpture weakly imbricate around antenna socket, otherwise shiny; frons punctures crowded (i=0 pd), sculpture weakly imbricate; vertex punctures dense laterally (i <1 pd), sparse medially (i=1–3 pd), sculpture shiny, sometimes weakly imbricate laterally; gena punctures moderately sparse (i =1–3 pd), sculpture shiny; postgena sculpture shiny; tegula punctures absent; scutum punctures dense (i <1 pd), becoming moderately sparse submedially and anteromedially (i =1–3 pd), sculpture shiny, becoming tessellate anteromedially; scutellum punctures dense marginally and on median line (i ≤ 1 pd), sparse submedially (i =1–4 pd), diversopunctate, sculpture shiny; metanotum sculpture shiny and finely, densely punctate (i <1 pd), becoming rugulose laterally; metapostnotum rugae strong, anastomosing or subparallel, not reaching margin, sculpture imbricate; preëpisternum sculpture shiny with crowded punctures (i=0 pd) or areolate; hypoepimeron punctures dense (i <1 pd), sculpture shiny or weakly imbricate; mesepisternum punctures dense (i <1 pd), sometimes becoming crowded dorsally (i=0 pd), sculpture shiny or weakly imbricate; metepisternum sculpture ruguloso-lineate dorsally, reticulate-punctate medially, imbricate ventrally; propodeum lateral face sculpture tessellate; propodeum posterior face sculpture tessellate; T1 anterior face sculpture shiny; T1 dorsal surface punctures moderately dense laterally (i=1–3 pd), becoming fine and very sparse medially (i=1–6 pd), absent in narrow median line, large apicolateral oval patches, and on rim, sculpture shiny, becoming weakly coriarious on rim; T2 disc punctures moderately dense (i=1–3 pd), disc sculpture shiny, rim punctures fine, sparse (i =1–4 pd), sometimes obscure, rim sculpture coriarious.

STRUCTURE. Face length/width ratio 0.8 (± 0.02 SD). Clypeus projecting ~67% below suborbital tangent; clypeal area length/width ratio 0.38 (± 0.03 SD); apicolateral denticles low rounded knobs; supraclypeal area length/width ratio 0.82 (± 0.08 SD). Forewing with 3 submarginal cells; pronotal angle obtuse; tegula shape normal. Intertegular distance 0.95 (± 0.06 SD) mm. Scutum length/width ratio 0.79 (± 0.04 SD); scutum/scutellum length ratio 2.79 (± 0.16 SD); scutellum/metanotum length ratio 1.53 (± 0.16 SD); metanotum/metapostnotum length ratio 0.73 (± 0.07 SD). Propodeum lateral carinae not reaching dorsal margin; oblique carina weak, straight. T2 depressed apical rim length less than 50% of segment. (n =7)

Male

COLOURATION. Head and mesosoma blue to blue-green; clypeus apical colour black to reddish brown; labrum reddish brown; mandible orange with black basal spot and red tip; flagellum reddish brown dorsally, orange ventrally; pronotal lobe reddish brown; metasoma black to reddish brown with rims of terga and sterna and downcurved lateral areas of terga becoming orange to translucent yellow, dark spiracular spots on T2–4; legs reddish brown with femur-tibia joints, base and apex of tibiae, and tarsi orange; tegula brown; wing membrane lightly infuscated, veins with subcosta dark brown, otherwise brown.

PUBESCENCE. Body hair colour white. Tomentum dense on face below eye emargination, pronotal angle and lobe, and space between pronotal lobe and tegula; sparse on gena, scutum lateral margin, episterna, and T3–5 basolaterally. Scutum hair thin to densely plumose. Sterna hair moderately long (1–2 OD), densely plumose, dense and erect. Wing hairs dark or light, short and dense.

SURFACE SCULPTURE. Clypeus punctures moderately dense (i=1–2 pd), sculpture shiny; supraclypeal area punctures moderately dense (i =1–2 pd), sculpture shiny; paraocular area punctures dense (i <1 pd), sculpture shiny; frons punctures dense (i <1 pd), sculpture shiny; vertex punctures dense laterally (i ≤ 1 pd), moderately sparse medially (i=1–2 pd), sculpture shiny; gena punctures sparse (i =1–3 pd), sculpture shiny; postgena sculpture shiny; tegula punctures absent; scutum punctures dense (i ≤ 1 pd), becoming moderately sparse submedially (i =1–2 pd), sculpture shiny, becoming weakly tessellate anteromedially; scutellum punctures dense (i ≤ 1 pd), sometimes becoming moderately sparse submedially (i=1–2 pd), sculpture shiny; metanotum sculpture shiny and moderately densely punctate (i=1–2 pd), becoming rugulose laterally; metapostnotum rugae strong, anastomosing, nearly reaching margin, sculpture imbricate; preëpisternum sculpture areolate; hypoepimeron punctures dense (i <1 pd), sculpture shiny; mesepisternum punctures dense (i <1 pd), sculpture shiny; metepisternum sculpture lineate dorsally, areolate ventrally; propodeum lateral face punctures obscure, sculpture imbricate and weakly rugulose; propodeum posterior face sculpture imbricate; T1 anterior face sculpture shiny; T1 dorsal surface punctures moderately dense (i=1–2 pd), sparse in large apicolateral oval patches (i =2–4 pd) and absent on rim, sculpture shiny; T2 disc punctures dense basally (i ≤ 1 pd), becoming moderately sparse toward premarginal line (i= 1–2 pd), disc sculpture shiny, rim punctures absent, rim sculpture shiny.

STRUCTURE. Face length/width ratio 0.78 (± 0 SD). F1:pedicel length ratio 0.73 (± 0 SD); F2:F1 length ratio 1.64 (± 0.13 SD); F2 length/width ratio 1.24 (± 0.04 SD); F9 length/width ratio 1.08 (± 0.04 SD). Forewing with 3 submarginal cells; pronotal angle obtuse; tegula shape normal. Intertegular distance 0.71 (± 0.04 SD) mm. Scutum length/width ratio 0.88 (± 0.01 SD); scutum/scutellum length ratio 2.63 (± 0.1 SD); scutellum/metanotum length ratio 1.56 (± 0.19 SD); metanotum/metapostnotum length ratio 0.8 (± 0.05 SD). Propodeum lateral carinae not reaching dorsal margin; oblique carina absent. (n =2)

GENITALIA. Not examined.

Range

Eastern California and western Nevada , just east of the Sierra Nevada Mountains ( Fig. 45 ).

Floral records

ASTERACEAE Giseke : Chrysothamnus • SALICACEAE Mirb. Salix L. S. exigua Nutt.

DNA barcodes

Not available.

Remarks

Rare. Only 9 specimens are known.

Figures

Fig. 43. Lasioglossum (D.) imbriumbrae sp. nov., ♀. A. Dorsal habitus. B. Face. C. Lateral habitus. D. Propodeum and metasoma. Scale bars: 1 mm.

Fig. 44. Lasioglossum (D.) imbriumbrae sp. nov., ♂. A. Dorsal habitus. B. Lateral habitus. C. Face. D. Propodeum and metasoma. Scale bars: 1 mm.

Fig. 45. Georeferenced collection records of Lasioglossum (D.) imbriumbrae sp. nov. (black squares) and predicted distribution by maximum entropy ecological niche modeling in Maxent (colour shading). Warmer colours indicate higher cloglog probability of occurrence.

Fig. 108. Mesepisternum. A. Lasioglossum (D.) eophilus (Ellis, 1914), ♀, entirely rugose. B. L. (D.) mesillense (Cockerell, 1898), ♀, ruguloso-punctate in dorsal half, smooth and distinctly punctate in ventral half. C. L. (D.) imbriumbrae sp. nov., ♀, entirely smooth and distinctly punctate. Scale bars: 0.5 mm.

Fig. 115. Flagellomeres. A. Lasioglossum (D.) festinum sp. nov., ♂, long. B. L. (D.) imbriumbrae sp. nov., ♂, short. Scale bars: 1 mm. Arrows indicate relative lengths of F1 and F2.