New-World Spread of the Old-World Robust Crazy Ant, Nylanderia bourbonica (Forel) (Hymenoptera: Formicidae)

            The robust crazy ant, Nylanderia bourbonica (Forel) (formerly Paratrechina bourbonica), is native to the Old-World tropics and subtropics. Its earliest known record in the New World was collected in 1924 in Miami, Florida. Here, I examine the subsequent spread of this species to other parts of North America and the West Indies. I compiled published and unpublished New World N. bourbonica specimen records from 446 sites, documenting the earliest known records for 24 geographic areas (countries, island groups, major islands, and US states), including nine for which I found no previously published records: Anguilla, Antigua, Barbuda, British Virgin Islands, Jamaica, Turks and Caicos Islands, Missouri, New York, and Washington. The vast majority of New World site records for N. bourbonica (89%) come from Florida, where this species is now known from 37 counties. Most, if not all, of the 14 site records of N. bourbonica in North American north of 30.5°N come from indoors. Although the earliest record of N. bourbonica from Cuba dates to 1933, the spread of N. bourbonica to many West Indian islands appears to be much more recent. In Florida, N. bourbonica is a widespread, though relatively minor household and agricultural pest, and also is common in some more natural environments. It remains to be seen whether N. bourbonica will become a significant pest in the West Indies or elsewhere in the New World.