Elaphidion pseudonomon Ivie

(Figs 1, 2, 11, 17, 19, 21)

Elaphidion pseudonomon Ivie, 1985: 312. Monné and Giesbert, 1995: 55. Monné and Hovore, 2005: 66. Valentine & Ivie 2005:280. [For a complete pre-1985 synonymy, see Ivie 1985.]

Elaphidion glabratum pseudonomon: Chalumeau and Touroult, 2005: 103.

This species has been a problem to distinguish throughout its more-than-100-year history (Ivie 1985). When two unit trays of 50 specimens each are placed side-by-side, the difference between E. pseudonomon and E. glabratum is so obvious that no one would question their distinctiveness. However, when faced with diagnosing these two highly variable species in such a way that every specimen can be identified in isolation, the situation is much more difficult, leading to polite and understandable questions by workers with only small series to work with. This has been aggravated by use of relative and weakly defined characters to diagnose these differences (e.g. Ivie 1985). Recently, Chalumeau and Touroult (2005) went so far at to consider E. pseudonomon a subspecies of E. glabratum. However, the definition of a subspecies generally includes “…and interbreeding successfully where their ranges overlap” (Lincoln et al. 1982), and there is no evidence of these two forms occurring together anywhere in their ranges. Therefore, they cannot be considered subspecies. In the absence of behavioral or genetic data most modern insect systematists consider two allopatric populations that exhibit consistent differences to have divergent evolutionary histories, and place them either as populations of the same taxon or recognize them as full species. After extensive work with these populations for (in the case of Ivie) nearly 30 years, we have found they consistently behave as species, and have identified several, albeit difficult, characters to distinguish them (see diagnosis under E. glabratum above). These differences correspond to a biogeographic boundary (the Anegada Passage), which divides the Greater and Lesser Antillean faunae, further strengthening our argument. We therefore return E. pseudonomon to full specific status.

DIAGNOSIS: See under E. glabratum. Length 9.5– 17 mm.

DISTRIBUTION: St. Thomas, St. John, Tortola, Guana (Valentine and Ivie, 2005), Virgin Gorda, Anegada. Puerto Rican record removed to E. mayesea.