08 December 2009

Suicidal slugs at noon


Within about a half hour period around noon today, I saw 5 of these slugs crawling on a dry sidewalk. One slug had already run out of steam, or rather, liquid water, in the middle of the sidewalk and was rapidly approaching its demise. I relocated it to the grass along with the other 4 who were totally oblivious to the risks of crawling on bone dry concrete.


They were about 2 to 2.5 cm long and black. Very Black. I had to lighten up the pictures in Photoshop considerably to make their skin features visible. I believe they were Deroceras laeve.


John said...

Interesting that they wouldn't have the instinct to stay off of such dry surfaces.

Kazimir Majorinc said...

It was nice that you returned them to the grass.

Anonymous said...

Hi Aydin. Yes, I said to myself Deroceras laeve when I saw your images, although in the British Isles I never saw one that dark; they were always pale to mid-brown in color. I was recently reading that here in the US there is also the introduced species Deroceras panormitanum which is supposedly very hard to tell apart from D. laeve and which is probably already present (as yet unrecognized) and widely distributed, even in the eastern states, having been introduced via nurseries and garden centers.

Other than by dissection, one is supposed to be able to tell the difference (some of the time) by the profile of the very end of the tail, which usually rises up from the sole vertically in D. parnormitanum. It's hard to say if yours does that from the images, but the lower image looks as if that might be the case. Apparently D. parnormitanum can be dark brown or almost black in color.

There's a paper at:

I wish I knew more about how to distinguish the two externally.
Susan J. Hewitt


Maybe I should dissect one to confirm the ID.

Anonymous said...

Well, I suppose having saved 5 lives from terminal desiccation, you are entitled to sacrifice one for the cause of science. It would be interesting to know if the species is present in Maryland. As it says in that Reise et al paper, D. parnormitanum was recorded from Washington DC and near Philadelphia in 2006, but prior to that it was not recorded in the eastern US, although recorded in greenhouses in Quebec in 1969. I would not be surprised if what you saw was not D. laeve because once you get beyond the first impression, to me they don't really look like that species: they look chunkier, coarser and thicker, both in their body shape and in the raised surface "fingerprint" pattern they have. To me, at least in Britain, D. laeve always had a very "dainty" "delicate" and "elegant" appearance (OK, it's not very scientific terminology!)

Apparently in Europe there are some other species of ''Deroceras'' that look very similar, such as Deroceras sturanyi. If more species get introduced and established here, it will be even harder to know what is going on when you see slugs that look like this.

Susan J. Hewitt

Megan said...

I agree with Susan that you might try dissecting one. Yeah, D laeve normally seems "daintier" and paler than the slugs on your sidewalk. But I've always had a hard time with anatomical dissections of D. laeve, which usually have underdeveloped, um, male organs and are functionally female.


Yes, that's the problem with D. laeve, especially this time of year when they tend to be aphallic. But that could be one way to tell it apart from other species.

xoggoth said...

You have just gone way up in my estimation for rescuing that nice little slug Mr O. Makes up for previous nasty experiments and dissections and the exploitation of them in your slug porno movies.