Nomada texana Cresson

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 : 18-22

Nomada texana Cresson

Figures 29, 30, 35, 36, 39, 41, 43

Nomada texana Cresson 1872: 271 [Lectotype: Academy of Natural Sciences, Philadelphia, Ψ; label data: “[ USA] Tex. [Texas]// 163// Ψ// Lectotype 2567 [red label]”]; Cresson 1916: 132 [lectotype designation].

Nomada heiligbrodtii Cresson 1878: 75 [Lectotype: Academy of Natural Sciences, Philadelphia, Ψ; label data: “[ USA] Tex. [Texas]// Ψ// Lectotype 2598 [red label] // ANSP”]; Cresson 1916: 120 [lectotype designation]. new synonymy.

Diagnosis. Nomada texana is most similar to N. tiftonensis , but can be differentiated from the latter species by the following characters: in both males and females, S3 and S4 each has a narrow, ivory or very pale yellow, transverse maculation that medially curves slightly anteriorly. The maculations are slightly interrupted medially or nearly so, and one observed specimen from Texas has maculations restricted to small areas laterally on S3 and S4. In contrast, in N. tiftonensis there are no maculations on any of the metasomal sterna. Also, in both males and females of N. texana on T3 there is an uninterrupted, yellow or ivory, transverse maculation ( Fig. 43), while in N. tiftonensis the maculation on this tergum is widely medially interrupted ( Fig. 44); however, there is often a faint area of paler brown integument connecting the two lateral yellow maculations, and in one specimen from Ontario the maculation is entirely uninterrupted. Females of the two species can be differentiated by characters of the hind tibia (viewed at high magnification): in N. texana , there are three to five, very wide and flat, transparent white to brownish, spine-like hairs (depending on the light reflection) whose apical tips are squared-off and extend only to the same length as, or slightly further than, the surrounding finer, white hairs ( Fig. 35 ); while in N. tiftonensis these specialized hairs number from seven to ten, increase more dramatically in size posteriorly along the apical margin, and are clearly longer than the surrounding, finer, white hairs; these hairs comparatively thinner than those of N. texana (though still thicker than in many other Nomada species), round in cross-section, and translucent yellow throughout most of their length but at least a few of the longest and posterior-most hairs have the bases translucent white and the apical tips opaque brown to dark red ( Fig. 37 ). Females of N. texana and N. tiftonensis can additionally be separated by the punctation of the clypeus relative to the paraocular area: in N. texana the punctures on the clypeus are distinctly smaller and denser than those on the paraocular area (punctures ranging in size from relatively small to large, Fig. 39 ), while in N. tiftonensis the punctures are almost exactly the same size and density on the clypeus as in the yellow portion of the paraocular area (punctures uniformly large, Fig. 40 ). Males of the two species are not as distinctly separated by the punctures of the clypeus, but in general the punctures are denser in N. texana than in N. tiftonensis (with significant overlap between the two species).

Males and females of N. texana and N. tiftonensis generally differ, sometimes subtly, in features of the antenna: the antenna (especially the scape, pedicel, and F1) is comparatively brighter yellow-orange in N. texana than in N. tiftonensis , with the antenna of most N. tiftonensis specimens dark brown with black on the posterior surface (when antennae directed dorsally) and dull orange markings on the anterior surfaces of the scape, pedicel and F1 (antenna of N. texana with much less contrast between the anterior and posterior surfaces). As discussed above, the density of punctures on the clypeus tends to be much lower in females of N. tiftonensis than in N. texana (length of space between punctures often greater than one puncture diameter in N. tiftonensis , spaces between punctures rarely greater than a puncture diameter in N. texana ), although in both species there is sometimes an impunctate longitudinal line at the center of the clypeus (this impunctate line sometimes very broad in N. tiftonensis ). The metasomal maculations of several specimens of N. texana are clearly ivory and most are pale yellow to near ivory, while in N. tiftonensis the maculations are entirely yellow. All observed specimens of N. tiftonensis have extensive amounts of black integument on the hind coxa, while in N. texana all but a few lack black integumental color and are instead entirely orange except for a yellow maculation present in both species; however, in a few specimens of N. texana there is a limited amount of black at the very base of the hind coxa and in the Maryland specimen the hind coxa is almost entirely black, except for dark orange shadings on the ventral surface.

Molecular results. We do not have molecular data from representatives of N. texana . Several specimens were sequenced that had previously been identified as N. texana , but upon closer examination they are in fact representatives of N. tiftonensis (see below).

Variation. Both of these very similar species have relatively low degrees of variability in most character states. In addition to the information presented in the description section, the extent of yellow/ivory on the male supraclypeal area varies in N. texana with all male specimens having pale maculations on the supraclypeal area, although the extent varies to a small degree.

Distribution. Nomada texana has a more southern and western distribution relative to N. tiftonensis , with specimens seen from Arizona and Idaho east to Texas and Indiana; we have also seen specimens from Georgia, Alabama, and Maryland.

Material examined. 35 specimens were examined from TX, ID, UT, NM, NE, GA, AL, NV, AZ, MD, and IN (Appendix).

Comments. Mitchell (1962) synonymized N. tiftonensis and N. modesta rivertonensis with N. heiligbrodtii , and then separated N. texana from N. heiligbrodtii based on the maculation pattern of T2 and T3. Based on the characters presented herein we disagree with his conclusions and instead believe that N. tiftonensis and N. modesta rivertonensis represent males and females of the same species, and that N. heiligbrodtii is a junior synonym of N. texana . Mitchell's (1962) keys to the males and females of Nomada , as well as diversity of names present on previously identified specimens in collections, reflect the general confusion between these two very similar species.

Based on the available material, N. tiftonensis appears to inhabit eastern sandy areas; all of the collection locales represented by the material, with which we are familiar, meet that general description. With the exception of the Maryland specimen, we are not familiar with the collection locales represented by the examined N. texana specimens and are therefore unable to comment upon them. However, the Maryland specimen is perhaps illuminating in that it was captured only a few miles from specimens of N. tiftonensis .

The soils of the capture site were silty clay soils (the region is famous for its bricks) while the N. tiftonensis specimens were captured in a restricted deep sand area along the Patuxent River (the only source of commercial sand in the region). It would be interesting to investigate the differences in the preferred sites. Hosts for both species are unknown.

Figures

FIGURES 33 – 38. Outer apical surface of hind tibia. Figs. 33, 34. Nomada fervida. Fig. 33. Female. Fig. 34. Male. Figs. 35, 36. Nomada texana. Fig. 35. Female. Fig. 36. Male. Figs. 37, 38. Nomada tiftonensis. Fig. 37. Female. Fig. 38. Male.

FIGURES 39, 40. Female clypeus and paraocular area. Fig. 39. Nomada texana. Fig. 40. Nomada tiftonensis. FIGURES 41, 42. Male face. Fig. 41. Nomada texana. Fig. 42. Nomada tiftonensis.