Eggs of Arion vulgaris are laid in clutches. Each egg is 3 mm in diameter. There are 45 eggs in this clutch and dimension of this clutch is 21 mm × 18 mm. This is a fresh clutch laid in the same day as the photo was taken.
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)
Why it is on those stones on these photos? It is because inhabits rocks and walls. It is quite common snail already described by Carl Linnaues in 1758. Linnaues used the specific name lapicida for this snail, because he thought that its mucus can dissolve limestone rocks. The Latin word lapis means the “stone”, the Latin suffix -cida means “cut out”. The Latin word lapicida means the “stonecutter”. It can not dissolve stones in fact.
(in Czech) Blažka F. (1892). Na venkově po dešti. Vesmír, 22(3): 5-6.
Lapicide. Wictionary, accessed September 12, 2014.
Etymology of the Latin word lapicida. myEtymology, accessed September 12, 2014.