Mating Slugs: Withdrawal - Type 1

I define the withdrawal phase in Lehmannia valentiana as beginning once both penes have fully retracted, which usually takes a few seconds. Following retraction, the slugs do not immediately separate but remain with their bodies intertwined, rubbing against each other with cephalic tentacles retracted or extended (sometimes alternating between the two), and nibbling each other's body mucus. Then one slug will initiate separation, slipping out of the coil and moving away. The other slug will usually stay behind to eat the leftover mucus and ejaculate on the mating surface. Sometimes neither slug eats it, and other times both slugs will leave only to return later. The reason for this is unknown, but Reise suggests, and I agree, that the consumption of mucus may serve to rejuvenate the slug after the energy-draining act of courtship and copulation.

Like courtship, withdrawal can take a variety of forms. In this post I'll be addressing Type 1, a common kind, in which one slug initiates separation and leaves, conceding, as it were, the mucus on the mating surface, which the remaining slug then devours. The first slug does not return, and the second slug stays on the site only until it has eaten its fill. No further contact is made between the two slugs, as if the separation is mutual.

Couple 9 exemplifies this behavior:

Just after retraction of the penes.