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A new species of Andrena (Trachandrena) from the Southwestern United States (Hymenoptera, Andrenidae)
expand article infoCory S. Sheffield
‡ Royal Saskatchewan Museum, Regina, Canada
Open Access

Abstract

A new species of Andrena Fabricius, 1775, subgenus Trachandrena Robertson, 1902 is described and illustrated, A. hadfieldi sp. nov., from Arizona, United States. The new species, presently known only from the female holotype, was collected in a Malaise trap in 1994, and remained unstudied until recently. In addition, Trachandrena is compared to similar subgenera in North America to assist in recognizing new members.

Keywords

Bee, new species, Trachandrena, North America, Arizona

Introduction

Andrena Fabricius, 1775 is one of the largest genera of bees, with 1,556 species (Ascher and Pickering 2020). Dubitzky et al. (2010) estimated that there are likely ca 2,000 species, suggesting there are many undescribed species, especially in Mesoamerica and in the dry regions of Central Asia. Though the genus is mainly Holarctic, it extends into Mesoamerica, parts of Africa and tropical Asia (Michener 2007).

The subgenusTrachandrena Robertson, 1902 is represented by 30 species globally (Gusenleitner and Schwarz 2002; Michener 2007), 24 of which occur in the Nearctic region (LaBerge 1973). Robertson (1902) originally described Trachandrena as a genus and included many species still placed in the subgenus today, but also included A. claytoniae Robertson, 1891 (= A. imitatrix Cresson, 1872) and A. crataegi Robertson, 1893. Viereck (1917) initially, and incorrectly applied the name Scrapter Lepeletier and Serville, 1828 (a genus of Colletidae) as a subgenus of Andrena for certain species, including among others A. imitatrix and A. morrisonella Viereck, 1917, but later (Viereck 1922) proposed Scrapteropsis because he felt it differed significantly from the Old World species incorrectly assigned to Scrapter (LaBerge 1971). Thus, Viereck (1924) recognized at least two subgenera of Andrena within Robertson’s (1902) initial concept of Trachandrena. Cockerell (1929) provided further discussion on Robertson’s (1902) Trachandrena, though in general supported Viereck’s (1924) opinion of subgeneric rank status, and also felt Robertson’s (1902) concept of Trachandrena likely involved multiple subgenera. For instance, Cockerell (1929) realized that the mainly eastern treatments of Robertson (1902) and Viereck (1924) were not fully representative of the western North American bee fauna and noted similarities of some of these to certain Old World species, sharing some characteristics with Trachandrena, but very distinct, particularly species with males that have a yellow clypeus. These taxa are now placed in the subgenusPlastandrena Hedicke, 1933, and most species in North America (excluding the mainly eastern A. crataegi) have males with a yellow clypeal maculation.

Lanham (1949) subsequently placed Scrapteropsis into synonymy with Trachandrena, and proposed subgenusMimandrena Lanham, 1949 (with type species A. imitatrix) for Trachandrena-like species which have a propodeal corbicula with plumose hairs internally, presumably not realizing (as per LaBerge 1971) that Viereck’s Scrapteropsis shared this feature (as indicated above, he included A. imitatrix in his subgenus). Lanham (1949), Mitchell T (1960) and LaBerge (1964) placed those species with simple internal hairs into the subgenusTrachandrena. Warncke (1968) later placed Trachandrena and Mimandrena into synonymy with the Old World subgenus Biareolina Dours, 1873, which is now considered monotypic (Michener 2007). LaBerge (1971) later reinstated Scrapteropsis as a valid North American subgenus, placing Mimandrena into synonymy. Species which Warncke (1968) placed in Bareolina are now included in Scrapteropsis (Nearctic only) or Trachandrena (Holarctic) (Michener 2007).

Robertson’s (1902) concept of Trachandrena suggested close affinities of Plastandrena, Scrapteropsis and Trachandrena which was supported in a recent morphology-based phylogeny (Dubitzky et al. 2010). In that work, Trachandrena was recovered as a taxon belonging to a larger clade (i.e., the Trachandrena clade) containing Scrapteropsis, Plastandrena, Agandrena Warncke, 1968 and Biareolina (Dubitzky et al. 2010), the latter two subgenera absent from the Nearctic (Michener 2007). However, in an earlier phylogenetic analysis using mitochondrial and nuclear DNA sequences, Scrapteropsis was not recovered as a monophyletic group, instead being interspersed within Trachandrena, with Plastandrena not as closely related (Larkin et al. 2006). The somewhat contrasting results from both studies (Larkin et al. 2006; Dubitzky et al. 2010) suggest that more analysis with more taxa included is required to resolve the relationship of Trachandrena to other subgenera.

Since LaBerge’s (1973) revision of the subgenusTrachandrena in the Nearctic region no additional North American species have been recognized. Here a new species of Trachandrena is described from Arizona, United States. A diagnosis and full description of the female is provided. In addition, a partial key, modified from that of LaBerge (1973) is provided to allow females of the new species to be recognized from other species.

Materials and methods

For consistency with species treatments published elsewhere, the description generally follows the format used by LaBerge (1973). Other terminology and measurement methods follow that of Michener (2007); body length was measured as the sum of the length from the antennal base to the posterior propodeal surface and the length of the metasoma in lateral view. The following abbreviations are used: F = flagellomere, numbered from base to apex; pd = puncture diameter; T = metasomal tergum, and S = metasomal sternum, both numbered from the base to apex.

Photomicrography was undertaken with a Canon EOS 5D Mark II digital camera with an MP-E 65 mm 1:2.8 1–5× macro lens. Measurements were made with an ocular micrometer on a Nikon SMZ1000 stereomicroscope.

Taxonomy

Family Andrenidae Fabricius, 1775

Subfamily Andreninae Fabricius, 1775

Andrena Fabricius, 1775

Andrena Fabricius, 1775: 376. Type species: Apis helvola Linnaeus, 1758, by designation of Viereck, 1912: 613.

Anthrena Illiger, 1801: 127, unjustified emendation of Andrena Fabricius, 1775.

Anthocharessa Gistel, 1850: 82, unjustified replacement for Andrena Fabricius, 1775.

Type species

Apis helvola Linnaeus, 1758, autobasic.

Subgenus Trachandrena Robertson, 1902

Trachandrena Robertson, 1902: 187, 189.

Type species

Andrena rugosa Robertson, 1891, by original designation.

Diagnosis

Trachandrena, particularly the females, are relatively easy to recognize among most other subgenera of Andrena in the Nearctic region based on the combination of the coarsely rugose metapostnotum (i.e., propodeal triangle) (Fig. 1) and the generally coarse body sculpturing (being less strongly sculptured in most other subgenera), the structure of the metasomal terga, especially T2, which have broad apical marginal zones that usually extend ½ the median length of the tergum (Fig. 2B) or more (Fig. 2A, C, D) (other subgenera in the Nearctic have narrower marginal zones), and the characteristic structure of the facial fovea, which is typically much narrower in the lower half (Fig. 3) (more parallel-sided for entire length in other Nearctic subgenera). As indicated above, in the Nearctic region Trachandrena is most similar to Plastandrena and Scrapteropsis. In addition to both of these subgenera having terga with much narrower marginal zones (Fig. 4), both sexes of Plastandrena usually have weakly to strongly curved inner hind tibial spurs (Fig. 5A) whereas these are straight in Trachandrena (Fig. 5B), and the facial fovea of females of both subgenera are typically broad throughout. Males of Scrapteropsis are difficult to distinguish from Trachandrena (Viereck 1924), though each has unique genital capsules (LaBerge 1971, 1973), the marginal zone of T2 is longer in Trachandrena, the antenna usually being slightly longer. Male Trachandrena also have S6 usually flat, not with a reflexed apical margin or with apicolateral teeth as in some Plastandrena (i.e., A. crataegi; LaBerge 1969; Michener 2007). In addition, most Plastandrena in North America, excluding A. crataegi, have the clypeus yellow or otherwise maculated (LaBerge 1969), not black as in Trachandrena.

Figure 1. 

Dorsal enclosure of propodeum (i.e., propodeal triangle) of a female Andrena rugosa Robertson, the type species of Trachandrena Robertson.

Figure 2. 

Dorsal surface of metasoma of female Trachandrena. A Andrena rugosa, the type species of the subgenus, with relatively wide apical impressed area of T2; B A. hippotes Robertson, with a relatively narrow apical impressed area of T2 (but still wider than basal area); C A. cleodora (Viereck); D A. hadfieldi, nov. sp. Both of the latter species have broad apical impressed areas of T2 which are impunctate.

Figure 3. 

Facial fovea of Andrena rugosa. The lower half of the facial fovea in Trachandrena is usually much narrower than the upper portion, though this species is the most extreme example.

Figure 4. 

Dorsal surface of metasoma of female A Plastandrena Hedicke, Andrena crataegi Robertson, and B Scrapteropsis Viereck, A. kalmiae Atwood. Both subgenera differ from Trachandrena Robertson in having the apical impressed area of T2 narrower than the basal area.

Figure 5. 

Inner hind tibial spur of A Plastandrena, Andrena crataegi, and B Trachandrena, A. hippotes.

Andrena (Trachandrena) hadfieldisp. nov.

Material examined

Holotype female, USA, Arizona, Santa Cruz Co., Patagonia Sonorita Creek Reserve, 31.53N, 110.77W, 14.iv.1994, M[alaise] T[rap], B. Brown & E. Wilk / Royal Saskatchewan Museum Entomology RSKM_ENT_E-219414. The single specimen is housed at the Royal Saskatchewan Museum (RSKM) in Regina, Saskatchewan, Canada. The dataset for Andrena hadfieldi is archived with Canadansys (http://community.canadensys.net/) under resource title "A new Trachandrena from the Southwestern USA" and can be accessed using the following: https://doi.org/10.5886/em2mri.

Diagnosis

The female of Andrena hadfieldi is unique among Trachandrena in the Nearctic region in having very wide (i.e., at least 2/3 of the median tergal length) marginal zones of T2-T4 which are shiny and impunctate (Fig. 2D), a feature shared only with A. cleodora (Viereck) (Fig. 2C). Andrena hadfieldi is smaller than A. cleodora (9 mm, versus 10–13 mm body length in A. cleodora), and differs from A. cleodora in having the terga black (Fig. 2D) instead of black with strong metallic bluish reflections (Fig. 2C), and in having entirely pale pubescence, including the scopa (Figs 6, 7); the hair on the metasoma (Fig. 2C) and scopa of A. cleodora are black, and the pubescence of the dorsum of thorax is yellowish to red (subspecies cleodora; widespread in western North America) or entirely black (subspecies melanodora Cockerell; known from southern California). The structure of the pubescence on the dorsum of the thorax also differs between these two species, being long, very thin, and weakly plumose in A. hadfieldi (Fig. 6), but shorter and densely plumose, almost scale-like, in A. cleodora (Fig. 8). The process of the labrum in A. hadfieldi is more than 3× as wide basally as long medially (Fig. 9A); in A. cleodora the labral process is larger, subtriangular, with the base 2.5× as wide as the medial length (Fig. 9B). The body surface sculpture of A. hadfieldi is much finer than for A. cleodora; as examples, the face of A. hadfieldi is generally more finely and sparsely punctate, with shiny interspaces > two pd on the lower paraocular area (Fig. 10A), while in A. cleodora the lower paraocular area is more coarsely and closely punctate (interspaces < pd) (Fig. 10B); the surface of the propodeal corbicula is smooth with a few short rugae in A. hadfieldi (Fig. 11A), while coarsely rugose in A. cleodora (Fig. 11B).

Figure 6. 

Holotype female of Andrena (Trachandrena) hadfieldi. Lateral view.

The male of A. hadfieldi is unknown.

Description

Holotype, female (Figs 6, 7, 9A, 10A, 11A, 12). Body length 9 mm; head length 1.9 mm; head width 2.5 mm; intertegular width 2.1 mm; fore wing length 6.9 mm.

Figure 7. 

Holotype female of Andrena (Trachandrena) hadfieldi. Dorsal view.

Colour . Black except as follows: F3-F10 dark reddish-brown below; tegula moderately translucent, brown, becoming reddish brown in posterior half; wing membranes slightly infumate, veins yellowish-brown; legs dark brown, apical tarsal segments reddish brown.

Figure 8. 

Dorsal thoracic surface of Andrena (Trachandrena) cleodora, showing the short, thick pubescence.

Structure . Labrum with process trapezoidal, more than three times as wide at base as long medially, apical edge entire (Fig. 9A). Clypeus with coarse, close round to irregular shaped punctures, becoming finer apically, interspaces shiny and linear, less than 0.5 pd, without obvious median impunctate line but with a small shiny subapical boss extending for less than 1/5th median length of clypeus (Fig. 10A). Supraclypeal area with distinct round punctures separated by 0.5 pd, surface rather shiny (Fig. 10A). Mandible short, extending beyond middle of labrum by about ¼ its length in repose. Malar space extremely short (Fig. 10A). Lower paraocular area shiny with small punctures separated by > two pd (Fig. 10A). Face above antennal socket with rugulae extending to ocelli, without obvious punctures. Facial fovea long, extending from middle level of lateral ocellus to basal edge of clypeus; lower portion narrow, from below level of antennal socket about 1/3 as wide as upper portion, outer edge slightly incurved from inner margin of compound eye just above level of antennal socket, this area smooth, shiny and impunctate (Fig. 10A). Compound eye just over three times as long as broad in frontal view, inner margin converging slightly toward mandibles. Genal area in profile about as broad as compound eye, surface shiny with minute punctures separated by 2 pd, posterior half dull with reticulate shagreening, without apparent punctures except near base of mandible. Vertexal area above lateral ocellus subequal to one ocellar diameter, dulled by crowded punctures and dense reticulate shagreening. Antennal scape length equal to combined length of F1-F3; F1 about 1.5 times as long as broad at apex, and 1.5 times longer than F2; F2-F5 quadrate, F6-F9 about 1.2 times longer than broad, F10 more elongate, about 1.5 times longer than broad.

Figure 9. 

Labral process of A Andrena (Trachandrena) hadfieldi, and B A. (Trachandrena) cleodora.

Pronotum somewhat shiny, with distinct punctures dorsally, separated by about two pd, laterally mostly impunctate with surface somewhat dull. Mesoscutum with large, round deep punctures, between parapsidal lines and posteromedially separated mostly by ½ to one pd, anteriorly and laterally separated by less than ½ pd, becoming somewhat rugosopunctate along anterior edge (Fig. 7), surface dull, reticularly shagreened. Scutellum similarly punctured though punctures slightly sparser anteriorly, and surface mostly shiny. Metanotum dull and tessellate laterally, becoming somewhat shiny and punctate medially. Metapostnotum with rather shallow but distinct rugae, these somewhat irregular (Fig. 12); dorsolateral and posterior surfaces of propodeum moderately coarsely rugosopunctate, tessellate, dull; propodeal corbicular surface moderately shiny, tessellate, with a few short rugae (Fig. 11A). Mesepisternum coarsely rugose and somewhat shiny. Metepisternum surface smooth, with a slight shine. Fore femur with base round in outline. Posterior hind tibial spur straight. Tarsal claws with a small subbasal tooth.

Figure 10. 

Face of A holotype female of Andrena (Trachandrena) hadfieldi, and B A. (Trachandrena) cleodora.

T1 shiny and largely impunctate, with basal area (= disc) punctures obscure, shallow, sparse, separated by ≥ 5pd; marginal zone impunctate and shiny, occupying about 3/5th of median length of tergum, a few sparse minute punctures visible at extreme lateral edge, surface smooth (Fig. 2D). T2 with marginal zone clearly longer than basal area (about 3/4th medial with); basal area shiny with punctures separated by one pd, a narrow dull impunctate area adjacent to gradulus; marginal zone smooth, shiny and impunctate (Fig. 2D). T3-T4 similar to T2 but marginal zone of T4 shorter, about 3/5th of median length of tergum (Fig. 2D). T5 with basal area broader than marginal zone, basal area tessellate, with distinct punctures separated by 2–3 pd, becoming closer adjacent to marginal zone (Fig. 2D); marginal zone dull, largely obscured by prepygidial fringe (Fig. 2D). Pygidial plate U-shaped with rounded apex about ½ as wide as base, with sharply pointed, internal, raised triangular area on median surface. S2-S5 with surface somewhat shiny, punctures uniformly dense, separated by 1 pd; S2 with a medial U-shaped depression.

Figure 11. 

Propodeal corbicula of A Andrena (Trachandrena) hadfieldi showing long plumose hairs on the dorsal and posterior surface, no hairs on the anterior margin, and long simple internal hairs, and the rather smooth surface, and B A. (Trachandrena) cleodora, with the surface coarsely rugose.

Vestiture . Generally white to pale yellowish (Figs 6, 7), somewhat reddish on mandible and apical margin of labrum. Propodeal corbicula with long plumose hairs on dorsal and posterior edges, lacking anterior hairs, with long simple hairs internally (Fig. 11A). Trochanteral flocculus complete. Tibial scopal hairs long and simple. Prepygidial fimbria and T6 with reddish brown hairs (Fig. 2D). Terga lacking apical fasciae except reduced to small lateral patches of sparse hairs on T2 and T3 (Fig. 2D); a few long pale subappressed hairs arising laterally from the premarginal line and overlaying marginal zone (Fig. 2D). T1 with sparse pale hairs laterally and on declivitous anterior surface (Fig. 2D). S2 to S5 with sparse, pale, elongate plumose hairs apically, these becoming longer laterally (i.e., ½ length of succeeding segment).

Figure 12. 

Holotype female of Andrena (Trachandrena) hadfieldi. Dorsal view, propodeal enclosure.

Male unknown.

Distribution

United States, southern Arizona.

Etymology

It is a privilege to name this new species after Canadian astronaut Col. Chris Hadfield for his many achievements as a pilot, astronaut, author, lecturer, and science educator.

Partial key to species of Trachandrena (modified from LaBerge 1973)

4(2) T2 with basal area (i.e., visible base of tergum to gradulus) less than half as long medially as apical area and often less than one-third as long (Fig. 2A, C, D) 5
T2 with basal area (i.e., visible base of tergum to gradulus) more extensive, at least half as long medially as apical area and often longer (Fig. 2B) 14
5(4) Mesoscutum with posteromedian area impunctate, or punctures separated by two or three or more pd; face above antennal socket rugose; metasoma often red Andrena striatifrons Cockerell
Mesoscutum with posteromedian area punctate, punctures usually separated by one or two pd, if by more than two pd, then face above antennal socket punctate or rugosopunctate, not strongly rugose; metasoma black or mostly so 6
6(5) Metasomal hairs entirely black or dark brown (Fig. 2C); leg hairs, including tibial scopa, brown to black or largely so 7
Metasomal hairs largely pale in color (Fig. 2D); at least scopal hairs and often leg hairs entirely pale in color (Fig. 6) 7a
7(6) T2-T4 with apical areas impunctate, often with metallic blue reflections (Fig. 2C); face above antennal socket with coarse longitudinal rugae, especially in upper half Andrena cleodora (Viereck)
T2-T4 with apical areas with fine but distinct punctures, without strong metallic blue reflections; face above antennal socket with rugae weak or absent, usually with deep punctures with interspaces shiny, or weakly shagreened Andrena cupreotincta Cockerell (in part)
7a(6) T2-T4 with apical areas impunctate (Fig. 2D) Andrena hadfieldi sp. nov.
T2-T4 with apical areas distinctly punctate (Fig. 2A) 8 (in LaBerge 1973)

Discussion

Nothing is known about the biology of this species as it is known only from the holotype female which was collected in a Malaise trap. However, like other Trachandrena in the Nearctic region, this is a vernal species that probably visits spring flowering trees and shrubs (LaBerge 1973). It is hoped that by publishing a full description of the new species and a partial key to the Trachandrena in North America that includes this species, that additional specimens, including the male, will be discovered in other entomology collections or through survey work. The American Southwest is one of the most diverse regions for bees globally (Michener 1979, 2007), so it is likely that many other bee species await recognition.

Acknowledgements

I am grateful to Prof. Laurence Packer, York University, Toronto, Canada for comments on an early draft of this manuscript. I also appreciate the assistance of Dr. Robert Minckley (University of Rochester, Rochester, NY), Dr. John L. Neff (Central Texas Melittological Institute, Austin, TX), and Dr. Doug Yanega (University of California, Riverside, CA) for searching their respective collections for additional specimens.

References

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