Worldwide spread of Roger's dacetine ant, Strumigenys rogeri (Hymenoptera: Formicidae)

Strumigenys rogeri EMERY, 1890 (Subfamily Myrmicinae, Tribe Dacetini) is a very small ant (total length ~ 2.5 mm) that nests in and under dead wood and preys on tiny soil arthropods. Strumigenys rogeri has spread to many parts of the world through human commerce. However, because S. rogeri workers are so small and slow moving, and they become motionless when disturbed, most people, including field biologists, remain unaware of their presence. To examine the spread of S. rogeri, I compiled specimen records from > 400 sites worldwide. I documented the earliest known S. rogeri records for 67 geographic areas (countries, island groups, major Caribbean islands, US states, and Canadian provinces), including many areas for which I found no previously published records: Antigua, Austral Islands, Barbados, British Virgin Islands, Comoro Islands, Grenada, Guadeloupe, Iles Eparses, Martinique, Nevis, Palau, Philippines, St Kitts, St Lucia, St Martin, and Tanzania. Strumigenys rogeri apparently originated in tropical Africa, where its closest relatives all live, but it has become widespread on tropical islands of the Indo-Pacific and the West Indies, and in peninsular Florida. Outside of Africa and Florida, there are only a small number of continental records of S. rogeri, including a few from South and Central America and just one from continental Asia, in peninsular Malaysia. It is unclear whether S. rogeri has not yet spread to these continental areas, whether continental ants have competitively excluded S. rogeri, or whether these ants have been simply overlooked in surveys of diverse continental faunae. There is little information on what impact S. rogeri may be having on the native mesofauna in its exotic range.