I may not live in a greenhouse, but that didn’t stop a greenhouse millipede (Oxidus gracilis) from paying my front door a visit. Greenhouse millipedes are not native to Louisiana, but the real question is where are they really from? Like many organisms that have a wide introduced range and poor documentation of introductions, the exact native range of this species is not certain, but is thought to be Japan (it is now found on all major continents).
When people think of invasive species, the first thing to come to mind are usually very conspicuous, costly and destructive examples like the zebra mussel and yellow jackets, which displace native species. Sometimes a distinction is made between invasive and introduced on the basis of whether the organism expands its range after introduction or stays localized, but with inconspicuous organisms this line is blurry. When I look back after a day of taking photos, I usually can find at least one introduced organism in the lot (often more, sometimes many more). We may not think of the greenhouse millipede as a destructive invader, but we don’t really know what the cumulative effects of countless introduced organisms to new regions will be. This is an ongoing debate among ecologists and conservationists, and I am nearly well versed enough to claim to have answers, but when the first millipede I have stumbled across in Louisiana is from Japan (and there are native millipedes here), it makes me scratch my head a bit.