urbpan | 365 Urban Species. #319: Greenhouse Slug

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urbpan. Location: My front step, Brookline.

Urban species #319: Greenhouse slug Milax gagates

It is fortunate, for small urban invertebrates and those of us who appreciate them, that this has been an uncommonly warm fall in Boston. I was excited this morning, while waiting for my ride, to discover a new slug--well, one new to me. At first I thought it was my first glimpse of a terrestrial mollusk native to New England, but some research, including a look at a slug key, proved otherwise.

This particular shell-less snail is probably Milax gagates, or greenhouse slug. The greenhouse slug is originally native to southwestern Europe, but has been transported around the world, from greenhouse to garden. It now occurs on both coasts of North America, the southeast coast of Australia, and the islands of Britain, Bermuda, the Canary Islands, and Easter Island (map). Not shown on that map, but also part of the greenhouse slug's range, is the ever put-upon (ecologically speaking) nation of New Zealand. It seems likely that in its new ranges it lives near cultivated and landscaped plants only. Most of the available information about this species relates to limiting its potentially deleterious effect on agriculture.

Features distinguishing this slug from others include the keel along the tail, and its color pattern. This last feature is variable, with some individuals tending toward very dark coloring. Some sources list the species as the "black keeled slug," especially the Australian sources.