Background Recently (2013-2014), several hover fly specimens from two localities in Benin and Cameroon (West and Central Africa) were caught from a species that we could not identify using existing identification keys for Afrotropical Syrphidae. Results Sequencing of the standard COI barcode region and a subsequent BLAST-IDS in BOLD revealed a 100 % sequence similarity with Toxomerus floralis from Suriname (South America). Species identification was subsequently confirmed by morphology and sequencing of part of the nuclear 18S rDNA gene. Significance The species is widely spread in Benin, Nigeria and Cameroon, and eggs, larvae and adults are abundant at several localities. Yet, the full extent of its geographic distribution within tropical Africa remains to be determined. This is only the second known established introduction of a non-African hover fly species in the Afrotropics. Interestingly, the larvae of the species are pollinivorous, which is a rare feeding mode within the subfamily Syrphinae. Moreover, it is the only Syrphinae species of which the larvae feed on pollen from two plant species from different families (Cyperaceae and Rubiaceae). This example illustrates how DNA barcoding may allow a fast and accurate identification of introduced species.