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Identification Atlas of the Vespidae (Hymenoptera, Aculeata) of the northeastern Nearctic region
CJAI 05, February 19, 2008
doi: 10.3752/cjai.2008.05

Matthias Buck, Stephen A. Marshall, and David K.B. Cheung

Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1

 

Species formerly included in A. catskill:
A. catskill A. albophaleratus
A. sp. A A. sp. B

Taxonomy of Ancistrocerus catskill and related species. The most recent edition of the Nearctic Hymenoptera catalogue (Krombein 1979) recognizes three subspecies of A. catskill: A. c. albophaleratus, A. c. halophilus and the nominate subspecies. The three forms show distinct differences in colouration but are morphologically nearly identical. The range of the nominate subspecies broadly overlaps with both of the other subspecies (A. c. halophilus is western and will not be considered here). The two eastern subspecies are traditionally separated on the colour of their pale markings (ivory in A. c. albophaleratus, bright yellow in the nominate subspecies). Originally, the three subspecies were described as different species (still recognized by Bequaert 1925) but later they were reduced to subspecies (Bequaert 1944a). Krombein (1967) first observed that both yellow and ivory specimens emerged from the same nests and proposed the synonymy of albophaleratus with catskill (synonymy not followed by Krombein 1979).
A careful examination of the A. catskill complex shows that it is comprised of at least four species in the eastern Nearctic (plus one additional species from western Canada). Further species will likely be recognised from other areas of the wide range of “A. catskill”. Based on two new characters (cephalic foveae and wing scale at the base of the costa), which have not previously been used to diagnose species in the genus, the eastern species of the A. catskill complex can be divided into two groups. Each group includes forms that are marked with either bright yellow or ivory. In typical A. catskill, in Ancistrocerus sp. A, and in the western A. spilogaster the cephalic foveae are very closely approximated and more or less fused (Fig. B3.12; a thin median septum between the foveae is usually visible; rarely the septum is thick). In contrast, the cephalic foveae of most Eumeninae are paired and clearly separated by a plateau-like, horizontal area of variable width (e.g., Figs A4.2, A4.7–10, B8.3–5). This is also true for A. albophaleratus, Ancistrocerus sp. B, and the remainder of the eastern Nearctic species of the genus (Fig. B3.13). Secondly, in A. catskill, Ancistrocerus sp. A. and A. spilogaster the costal scale (i.e., the scale-like elevation at the base of the costa of the fore wing) is more produced than in other species (its outline is strongly convex in anterolateral view; its rim is acute in lateral view; its medial process is more salient in posterolateral view; Fig. B3.10). In A. albophaleratus and Ancistrocerus sp. B this scale is slightly convex in anteroventral view, its rim is more rounded and its medial process not salient (Fig. B3.11). Another species with separated cephalic foveae occurs in western Canada, but differs from similar eastern species by having a convex wing scale. The species pairs A. catskill/sp. A and A. albophaleratus/sp. B differ from each other by the extent of pale markings in the female (see key; at present no characters are known that will separate males). With the exception of Ancistrocerus sp. A (marked with ivory), all species occur in a bright yellow and in an ivory colour form.

 

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