Nomada lehighensis Cockerell

Droege, Sam, Rightmyer, Molly G., Sheffield, Cory S. & Brady, Seán G., 2010, New synonymies in the bee genus Nomada from North America (Hymenoptera: Apidae), Zootaxa 2661, pp. 1-32 : 14-18

Nomada lehighensis Cockerell

Figures 9–12, 19, 20, 45–50

Nomada lehighensis Cockerell 1903: 605 [Holotype: Academy of Natural Sciences, Philadelphia, Ψ; label data: "[ USA] Lehigh Gap, Pa. [Pennsylvania]// 7.1.97 [1 July 1897]// Ψ// P43// Type No. 10147 [red label]// N. lehighensis Ckll Type "].

Nomada kingstonensis Mitchell 1962: 420 [ US National Museum of Natural History, Ψ; label data: “[ USA] Kingston, R.I. [Rhode Island], Apr. 26 ’04 [26 April 1904]// R I College, Lot 80, No.1, Collection// Nomada perplexa Cr. Ψ// HOLOTYPE Nomada kingstonensis Mitchell [red label]// Type No. 75221 U.S. N.M.// USNM ENT 0 0 533940 [yellow barcode label]”] new synonymy.

Diagnosis. Females of N. lehighensis are likely to be confused with eastern North American Nomada species that possess thin, white to reddish, spine-like hairs on the outer apical margin of the hind tibia (e.g., N. pygmaea Cresson , N. sayi Robertson , and N. illinoensis Robertson ) due to a very similar appearance of their general habitus. However, N. lehighensis can be differentiated from those species by the presence of two to four (typically three) very stout, dark red, spine-like hairs that are evenly spaced along the outer apical margin of the hind tibia, and which do not project beyond the surrounding white hairs ( Fig. 19 ). As is typical of many Nomada species, there is a single, long, thin hair between the row of stout, spine-like hairs and a short triangular projection at the outer apical corner of the tibia that is present in nearly all species of Nomada . In combination with the hair pattern found on the hind tibia, the pattern of yellow maculations on the metasoma is usually diagnostic (Figs. 10, 11): in a few specimens there are no markings whatsoever, but in the majority, on T2–T5 each terga has a very small yellow dot (at times minute and sometimes with two dots) on the far lateral surface (in fact, so far laterally that they are not visible in dorsal view). The observed variability in maculation pattern progresses from a yellow dot present laterally only on T2 (for lightly-maculated specimens) to yellow dots present on T2 and T3, to yellow dots present on T2, T3 and T5, and finally (for the most heavily-maculated specimens), to yellow dots present on T2–T5 including T4. The dots increase slightly in size with more heavily-maculated individuals; however, as the extent of the maculations increases, the enlargement of the dots occurs medially, creating a more rectangular maculation, progressing to a more broadly transverse set of maculations (these maculations not joining medially and usually absent at the midpoint of the terga), maculation extent finally progressing to T3 possessing a second, sublateral, round, yellow spot similar in size to, but not conjoined with, the far lateral yellow maculation (a second, sublateral yellow spot has not been observed on T2). Unlike many species, in N. lehighensis the scutellum is pillow shaped, lacking a median longitudinal depression or furrow. The pseudopygidial area is also diagnostic in this species: compared to other species, it is relatively long, extending basally rather far onto the disc of T5, and is comprised of comparatively long and coarse hairs (Fig. 12). Finally, the preoccipital margin of the gena is carinate to subcarinate.

As in females, males of N. lehighensis have a similar habitus to species such as N. sayi , N. illinoesnsis , and N. pygmaea . In N. lehighensis , both the head and the mesosoma are largely black, with no yellow maculations present on the mesoscutum, propodeum, or mesepisternum (Fig. 10). One individual has small yellow markings on the pronotal collar, and another examined specimen has two large red circles on the scutellum. Males of N. lehighensis can be distinguished by the two to four large, stout, spine-like hairs on the outer apical margin of the hind tibia (as with most male Nomada , these stout, spine-like hairs are not as large as in the females, and tend toward translucence, making them more difficult to see in the males) ( Fig. 20 ). The yellow maculation pattern found on the metasomal terga is more extensive than that of the females, but follows the general pattern described above. However, in at least one specimen examined the lateral yellow maculations were poorly differentiated from the dark orange background integument of the terga, especially on T2–T4 (thus these maculations could be described as either complete or medially interrupted). T6 has vague, dark orange to yellow maculations that are poorly differentiated from the background color of the integument.

Description of male. Total length: 7.5–8.0 mm; forewing length: 6.0–6.5 mm.

Color: Figure 10. Head and mesosoma predominantly black, with the following areas yellow to pale brownish orange: basal two-thirds of mandible, labrum, clypeus, malar space and ventrally on paraocular area, anterior surface of antenna (scape usually yellow, pedicel and flagellar segments often pale brown to orange), sometimes posterior surface of apical flagellar segments, sometimes anteroventral corner of gena near malar space, pronotal lobe, tegula, sometimes entirely or in spots on scutellum, sometimes on anterior surface of mesepisternum, and most of legs except basally on coxae, posteriorly on trochanters, femora, and sometimes tibiae, reddish brown on entire tarsi. Forewing weakly infuscate to clear along most of length, more strongly infuscate at apical tip beyond closed cells. Metasoma predominantly brownish-red, with the following areas black: basally and sometimes apically on T1, less commonly basally and apically on T2–T6, and basally on S1; the following areas yellow: forming dots or quadrate maculations laterally on T2–T4, sometimes also forming lateral dots on T1 and T5, sometimes forming submedian dot or transverse maculation on median half or third of S2–S4, sometimes forming small dot midapically on T5.

Pubescence: Head and mesosoma (excluding mandible, flagellar segments, tegula, propodeal triangle, and parts of legs) densely covered with white, minutely branched, subappressed to erect hairs intermixed with white to clear, unbranched, erect hairs. Mandible with sparse row of long, unbranched hairs on ventral margin. Flagellar segments densely covered with minute, unbranched, appressed hairs. Tegula, especially near margins, with dense, unbranched, subappressed hairs. Propodeal triangle lacking hairs. Midtibia with dense, golden, simple, subappressed hairs along anterior margin of outer surface. Hind tibia with two to four, stout, reddish, spine-like hairs along outer apical margin and with a single, white to translucent, thin, long hair between spine-like hairs and posterior corner ( Fig. 20 ). Entire forewing (except basally) densely covered with short, brown hairs and lacking visible papillae. Metasoma mostly covered with sparse, short, suberect to appressed, unbranched hairs; in addition, with long, erect to suberect, simple hairs forming weakly defined, transverse row of hairs where basal yellow to orange-brown and apical reddish-brown to black integument meet on T3–T4 and S1–S5 (these hairs restricted more laterally on posterior sterna); long simple hairs more densely covering discs of T6 and T7 (T5–T7 laterally and T7 ventrally on pygidial plate with erect, simple hairs particularly long). S6 with apical tip covered with dense brush of short, unbranched, ventrally directed hairs.

Punctation: Punctures on face below frons largely obscured by hairs, except paraocular area adjacent to eye largely lacking hairs and with sparse, minute punctures. Frons, vertex, and gena with punctures relatively coarse, separated by about a puncture diameter (punctures larger on vertex and gena than on frons). Hypostomal area with punctures relatively wide and shallow. Mesosoma with punctures coarse, deeply impressed, and nearly contiguous to separated by a puncture diameter (especially on mesoscutum and dorsal half of lateral surface of mesepisternum) except as follows: metanotum with punctures fine and nearly contiguous, metespisternum and lateral surface of propodeum immediately above hind coxa with punctures less deeply impressed and less distinct from background integument due to weak striations on these sclerites; propodeal triangle with dorsal fifth very weakly reticulate, ventral fourth-fifths granulose to weakly striate near ventral margin; pronotal lobe and especially tegula with punctures minute, separated by 1 to 3 puncture diameters; legs with punctures less deeply impressed and especially on portions of inner surfaces with punctures absent. T1, T2, and basally on T3 and T4 with punctures minute, nearly contiguous, and weakly impressed; T3 and T4 apically, and T5–T7 with punctures increasingly larger and slightly more deeply impressed, separated by up to a puncture diameter. Sterna excluding very weakly granulose apical margins on S1–S5 with punctures small, weakly impressed, and separated by about a puncture diameter.

Structure: Mandible long, simple, apically pointed. Malar space larger near acetabulum (condyle nearly touching ventral margin of eye). Pedicel partly enclosed by scape. F2 one-third to one-half longer than F1, and one-fourth to one-third larger than F3; remaining flagellar segments subequal, each segment gradually decreasing in length moving apically; F11 nearly twice length of F10. Interantennal area with weak tumescence and moderate longitudinal carina extending posteriorly to midpoint of frons, gradually decreasing in height posteriorly. Preoccipital margin smoothly rounded, not carinate. Pronotal collar in dorsal view with apical margin not distinctly carinate, straight, reduced almost to nothing at midpoint, length laterally about 1.0 OD. Malus with relatively short apical spine distinctly separated from vellum by notch; apical spine with minute hairs on ventral margin. Hind tibia with small but distinct rounded triangular process on posterior corner of outer apical margin. Hind tibial spurs relatively straight, with outer spur nearly one-fourth shorter than inner. Forewing with three submarginal cells. Pygidial plate about a fourth longer than basal width, carinate along margin, and strongly emarginate medially at apex. S7 as in figure 45, S8 as in figures 46 and 47, and genital capsule as in figures 48–50.

Molecular results. We obtained DNA barcoding data from 20 specimens of N. lehighensis (16 females and 4 males) sampled from widely separated localities in Canada (Nova Scotia, Ontario, Alberta, British Columbia) and the United States (Pennsylvania, California, Washington) ( Table 1). The sequence divergence among these specimens ranged from 0–1.8%. Male specimens possessed sequences identical to that of female specimens in several cases, providing further evidence for the gender association in these species.

We note that our ongoing DNA barcoding work seems to support a cluster of genetically similar specimens that can be categorized into three separate morphological groups with affinities to N. lehighensis . Herein we are describing only one of those groups (i.e., the one that most closely matches the holotype specimen of N. lehighensis ). The remaining morphological groups appear to be distributed in more southern locations throughout the United States, and will be described in a later treatment.

Variation. For both males and females, the extent and pattern of yellow maculations on the metasoma is extremely variable. We have seen a relatively long series of female specimens and the maculation pattern can vary from none to modest amounts on all the terga except T1, which in all cases lacks yellow maculations (see Diagnosis). The amount of black integumental color on the mesoscutum varies progressively from only a small section along the median anterior margin, to a black stripe extending longitudinally along the side, to a stripe extending longitudinally down the middle, to an additional black stripe between the lateral and central areas of black integument. Similarly, and usually corresponding to the degree of black integument on the mesoscutum, the amount of black integument on the face varies from a small patch surrounding the ocelli to a large coalesced patch surrounding both the ocelli and the antennal bases.

The variation in the males of N. lehighensis (based only on two individuals) is listed in the Diagnosis, above; however, based on experience with similar species we speculate that there may be individuals of N. lehighensis that have extensive areas of red integument, particularly in the Southern Appalachians.

Distribution. Nomada lehighensis is a largely northern species that likely is tolerably common but underreported due to confusion with other species. We have seen specimens from the Maritimes to British Columbia and further south in the East in more mountainous regions. In eastern North America the species ranges as far south as the Great Smoky Mountains, and specimens have been collected from the Fall Line in the Washington, D.C., area, but it is not known from the Atlantic Coastal Plain proper.

Material examined. 31 specimens were examined from ME, BC, WA, RI, DC, PA, NC, VA, NJ, CT, ON, CA, NS, AB (Appendix).

Comments. This is the first description of the male of N. lehighensis of which we are aware. As discussed above, this species is likely under-reported due to its similar appearance to other common species. It is perhaps not surprising that the male had not been previously described given the taxonomic uncertainties that have frequently confused identifications in the past. The most important diagnostic character for distinguishing male N. lehighensis is the sparse number of stout, spine-like hairs on the hind tibia.

The holotype of N. kingstonensis was described based on a single female, and its taxonomic placement was likely complicated by the faded color of the integument. Because the holotype is faded, it is difficult to discern the pattern of the maculations present, particularly on the metasomal terga; however, the holotype appears to have the distinctive small yellow spots at the far lateral surface of T2 along with other diagnostic characters of N. lehighensis , including the hair pattern on the hind tibia, the weakly carinate preoccipital margin of the gena, and the general pattern of black integument throughout the body.

Figures

FIGURES 19, 20. Outer apical surface of hind tibia of Nomada lehighensis. Fig. 19. Female. Fig. 20. Male. FIGURES 21, 22. Scutellum, metanotum, propodeum, and propodeal triangle of female Nomada. Fig. 21. Nomada bethunei. Fig. 22. Nomada fragariae.