Mutillidae (Hymenoptera) from Essex Co., Virginia: monthly changes in abundance and richness

We analyzed the abundance and richness of velvet ants (Hymenoptera: Mutillidae) in Essex County, Virginia, USA. Also, to compare the species list in this study with the known diversity in the state of Virginia, we examined literature searches and collection inventories. Mutillidae specimens in Essex were sampled from March 26 to November 5, 1991, using 13 Malaise traps. The monthly abundance of each genus was then compared using Rayleigh and Mardia-Watson-Wheeler tests. Fieldwork yielded a total of 3302 specimens, distributed in 25 species, eight genera (Dasymutilla Ashmead, Ephuta Say, Lomachaeta Mickel, Myrmosa Latreille, Photomorphus Viereck, Pseudomethoca Ashmead, Sphaeropthalma Blake, and Timulla Ashmead), and three subfamilies (Myrmosinae, Mutillinae, and Sphaeropthalminae). The four most abundant genera were Pseudomethoca (789 specimens, four species), Myrmosa (778 specimens, one species), Ephuta (774 specimens, five species), Sphaeropthalma (662 specimens, one species). Myrmosa unicolor Say and Sphaeropthalma pensylvanica (Lepeletier) were the most abundant species, representing 44% of the collected specimens. The genera analyzed presented significant monthly abundance values, with maximum abundance values in June for Sphaeropthalma, July for Timulla, Dasymutilla, Myrmosa, and Photomorphus; August for Ephuta; and September for Pseudomethoca. Genera with similar patterns are Timulla-Dasymutilla, Timulla-Photomorphus, and Dasymutilla-Photomorphus. The 25 species recorded from Essex County in this study constitute 78.1% of the 32 species recorded from the state of Virginia. We concluded that the Mutillidae from Essex Co. displays large variations in abundance, with peaks of activity occurring from June to September. Although our study did not sample environmental variables, the monthly activity patterns observed are correlated with temperature patterns observed for Essex Co. in 1991. Finally, Sphaerophthalma (sic!) (Photomorphus) rubroscutellatus Bradley was recognized to be a junior synonym of Photomorphus impar (Melander).