As noted above, Eardley (1983) reviewed the taxonomic status of all names included in Xylocopa subgenus Xenoxylocopa by Hurd and Moure (1963) except X. chiyakensis, which was described from material collected in Angola outside the geographic scope of Eardley’s study. The name X. chiyakensis (Cockerell, 1908) has been applied by authors including LeVeque (1928) and Hurd and Moure (1963) to large-bodied female carpenter bees belonging to Xylocopa subgenus Xenoxylocopa which have yellow (as opposed to white) pubescence on the sides of the mesosoma, the scutellum, and the base of the metasoma. However, the material of this subgenus in USNM also includes both small-bodied females with yellow pubescence and large-bodied females with white pubescence, suggesting that the color characters provided by Cockerell (1908) may not actually correlate with the body size characters.

Cockerell (1908) used total body length and forewing length as diagnostic characters in a key to separate his Mesotrichia chiyakensis (said to have total body length 30 mm and forewing length 26 mm) from X. inconstans (said to have total body length of 26 mm and forewing length 21–23 mm). In the material examined, females with yellow pubescence (n = 7) had an average head capsule width of 9.1 mm (range 8.2–10.0 mm) while females with white pubescence (n = 17) had an average head capsule width of 9.0 mm (range 8.0–10.2 mm). Females with yellow pubescence had an average total body length of 27.6 mm (range 24.5–30.0 mm) while females with white pubescence had an average total body length of 25.3 mm (range 19.8–29.0 mm). Females with yellow dorsal pubescence had an average right forewing length of 24.7 mm (range 21.8–30.0 mm) while females with white dorsal pubescence had an average right forewing length of 24.0 mm (range 21.0–30.0 mm).

Given the significant overlap in these sets of measurements between female specimens with yellow pubescence and female specimens with white pubescence, and the fact that the averages of these measurements differ by just 0.1 mm (average head capsule width), 2.3 mm (average total body length), and 0.7 mm (average right forewing length), it does not appear that female specimens with yellow pubescence and female specimens with white pubescence differ significantly in these measurements of body size. Thus, the use of female body size to separate X. chiyakensis and X. inconstans, as proposed in the key of Cockerell (1908), does not appear to be tenable.

Male reproductive structures of X. chiyakensis were illustrated by LeVeque (1928) and those of X. inconstans were illustrated by Eardley (1983). Given the significant differences in size and style of these authors’ illustrations, it is difficult to tell from a comparison of these illustrations alone whether significant diagnostic differences are actually present. For this study, I examined the original dissection prepared by LeVeque (1928) from which her line drawing of the male genitalia of X. chiyakensis was derived. From my examination of this dissection, it is clear that the illustration provided by LeVeque (1928) shows the male genital capsule rotated slightly, suggesting that the dissected parts were likely drawn with a camera lucida or similar device, and thus the outline and general appearance of these structures may not be strictly comparable to the illustrations provided by Eardley (1983). Furthermore, the broad lines and small overall size of the illustration provided by LeVeque (1928) actually obscure important structural features of the genital capsule. Accordingly, I have provided a new, photographic image of the dorsal and ventral surfaces of this dissected male genital capsule here (Figure 4). Comparison with my own dissections of X. inconstans male reproductive structures from other localities and comparison with the illustrations provided by Eardley (1983) of the male reproductive structures in X. inconstans do not reveal significant differences between male reproductive structures in these two forms.

LeVeque (1928) mentioned that the male specimens available to her of X. chiyakensis from central Africa had slightly darker and more brownish pubescence than the male of X. inconstans, which she knew only from the description by Radoszkowski (1876). Differences in coloration can provide important diagnostic information at the species level for males of Xylocopa species (see, for example, Eardley 1983 and Hurd 1978). However, the male specimens that I examined from LeVeque’s material had evidently been immersed in some preservative prior to pinning, as their pubescence is matted and discolored. This may be the source of the reported color variation, as the male specimens that I examined from northern Zambia and southwestern Tanzania all had lighter colored pubescence which is similar in color to that of males from southern Africa and Ethiopia.

Finally, Eardley (1983) presents compelling evidence that females with yellow pubescence and females with white pubescence are both present in southern African populations of X. inconstans, and that in at least one instance females of the two different color forms were even found within the same nest.

Given this combined evidence, and the lack of clear, reliable diagnostic features which could be used to separate X. chiyakensis and X. inconstans, I have no difficulties in placing X. chiyakensis in synonymy with X. inconstans, new synonymy. Given the fact that the original description of X. inconstans by Smith (1874) emphasized both the body size variation and the color variation that occurs among females of the species, it is frankly difficult to understand how and why the yellow female color form was subsequently given three separate Latin names by three different workers.

The full synonymy for this species is therefore as follows:

Xylocopa inconstans Smith, 1874

Xylocopa abyssinica Radoszkowski, 1876

Xylocopa inconstans var. flavescens Vachal, 1899

Mesotrichia chiyakensis Cockerell, 1908, new synonym

Xylocopa inconstans var. flavocincta Friese, 1909

Females and males of the subgenus Xenoxylocopa can be readily separated from species in the other African subgenera of the genus Xylocopa using combinations of adult external morphological characters. Females and males of the widespread subgenus Koptortosoma Gribodo, 1894 are most similar to the species of subgenus Xenoxylocopa in terms of their overall appearance and coloration in both males and females (Hurd and Moure 1963). In my experience and that of my colleagues (Mawdsley et al. 2016), certain common and widespread species of the subgenus Koptortosoma are often found in association with the species of the subgenus Xenoxylocopa; however, species of these two subgenera can be readily separated using certain combinations of adult external morphological characters. In particular, the following characters will help to separate species of Xenoxylocopa from sympatric species in the closely allied subgenera Koptortosoma and Mesotrichia Westwood, 1838.

Female (Figures 1, 2). Head capsule broad and massive, space behind eyes greatly expanded. The space behind eyes is not greatly expanded and the head capsule is not as broad and massive in females of subgenera Koptortosoma and Mesotrichia.

First metasomal tergite lacking a distinct invaginated acarinarium or “mite chamber.” The acarinarium is present in females of subgenera Koptortosoma and Mesotrichia.

Small tooth present on either side of the median pygidial spine. This tooth is absent in females of subgenera Koptortosoma and Mesotrichia.

Male (Figures 3, 4). Frons very broad, maximum distance between compound eyes across frons greater than the vertical length of the compound eyes. The frons is narrower in males of subgenera Koptortosoma and Mesotrichia.

Inner margin of compound eyes with a distinct groove parallel to and adjacent to the eye margin. This groove is absent in males of subgenera Koptortosoma and Mesotrichia.

Figure 1–4. 

1 Adult female of Xylocopa (Xenoxylocopa) inconstans Smith, collected by the author at Skukuza, Kruger National Park, Mpumalanga, Republic of South Africa, on flowers of Peltophorum africanum Sonder (Fabaceae) 2 Adult female of Xylocopa (Xenoxylocopa) inconstans Smith, collected at Garamba, Democratic Republic of the Congo, and identified by Norma LeVeque as X. chiyakensis (Cockerell) 3 Adult male of Xylocopa (Xenoxylocopa) inconstans Smith, collected at Kruger National Park, Mpumalanga, Republic of South Africa 4 Dorsal (left) and ventral (right) views of the male genital capsule of Xylocopa (Xenoxylocopa) inconstans Smith, collected at Faradje, Democratic Republic of the Congo, dissected and illustrated by Norma LeVeque (1928, figure 16) as the male genitalia of X. chiyakensis (Cockerell).

Michener (2007) provides keys for separating species of subgenus Xenoxylocopa from the other Old World subgenera of Xylocopa, while Eardley (1983) provides keys for separation of both sexes of X. inconstans from the other species of Xylocopa in southern Africa. At this writing, the Michener (2007) keys and text are available online at: http://base.dnsgb.com.ua/files/book/Agriculture/Beekeeping/Thep-Bees-of-the-World.pdf.

The following keys were developed to separate species of the subgenus Xenoxylocopa from species of continental African subgenera which belong to what I call here the “Mesotrichia Group,” a morphologically well-defined group of Old World subgenera within Xylocopa which may ultimately prove to be a distinct monophyletic group (as suggested by the phylogenetic analyses of Minckley (1998)). Females of the continental African species in this group can be readily separated from those of other continental African Xylocopa subgenera by the presence of a sharp transverse ridge on the scutellum which divides the scutellum into two distinct surfaces, a more or less horizontal dorsal anterior surface and a more or less vertical posterior surface. Males of the continental African species in this group of subgenera have a somewhat similar modification to the first metasomal tergite, which is divided by a transverse ridge into a more or less horizontal posterior surface and a more or less vertical or sloping anterior surface. In other continental African subgenera of Xylocopa, the scutellum is rounded or feebly angled in females, while the first metasomal tergite is sloping or rounded in males. The following key is based on adult morphological characters which were originally identified and used in keys by Hurd and Moure (1963), Eardley (1983), and Michener (2007), and which were confirmed through my own examination of specimens of these subgenera in USNM.