I found a slug Arion fuscus dangling on its mucus thread. I found it on a waste container in the street, in Olomouc city, the Czech Republic, on the September 16, 2014. Such species usually live in woods, but it can be found in gardens too.
It was moving down quite fast. The difference between the first and the second photo is 20 seconds.
As we know, some snails and slugs can move down on the mucus thread like a spider on a spider thread. Such locomotion is considered to be unusual.
There is a detail of Arion fuscus cropped from the first photo:
Breure B. 2011: “Dangling snails – an update“. Bram’s snailblog.
Breure B. 2011: “Dangling snails – update (2)“. Bram’s snailblog.
Breure B. 2013: “Dangling Jamaican snail“. Bram’s snailblog.
Wiktor A. & Stawarczyk T. 2012: “AN UNUSUAL MODE OF LOCOMOTION OF AN ECUADOREAN SLUG BELOCAULUS SP. (MOLLUSCA: GASTROPODA: VAGINULIDAE)“. Folia Malacologica 19(4): 277–278. (PDF free download after free registration)