Worldwide Spread of the Graceful Twig Ant, Pseudomyrmex Gracilis(Hymenoptera: Formicidae)

James K. Wetterer


Pseudomyrmex gracilis is a large, slender arboreal ant with a painful sting. This species has a broad native range spanning much of the New World tropics and subtropics. In addition, P. gracilis has established exotic populations, notably in Florida and Hawaii. Here, I compiled and mapped records of P. gracilis from >1500 sites in 32 geographic areas (countries and US states) to evaluate its worldwide distribution and update information on its recent spread. Pseudomyrmex gracilis has an essentially continuous distribution ranging from southern Uruguay (34.9°S) and central Argentina (34.5°S), through much of South and Central America, to southern Texas (31.3°N), with recent records (all since 1995) in southern Louisiana (29.9–31.3°N). Populations of P. gracilis were first discovered in southeast Florida in 1960. Since then, P. gracilis populations have expanded northward in Florida, up to 30.8°N. In 2009, a P. gracilis population was discovered in Mississippi (30.6°N). Genetic analyses are needed to determine whether the recent appearance of P. gracilis in Louisiana and Mississippi has resulted from this species expanding its range eastward out of Texas or westward out of Florida. Exotic populations of P. gracilis in Hawaii were first found on Oahu in 1976. There are now >20 reports of P. gracilis from Oahu, Kaho'olawe, and Maui, suggesting that the Hawaiian populations are expanding. Finally, there are a few exotic records of P. gracilis from the West Indies: Barbados, Guadeloupe, and Jamaica. It remains to seen whether or not the wide-ranging P. gracilis, which has become so well established across Florida, will show comparable success in Hawaii and other regions it has invaded.

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