But is it art? II

Any idea what this is on my garden fence?  The drunken daubings of a novice graffiti artist, perhaps?  Amazingly, and I hope you won't feel repulsed at this (I'm having a nature-geek moment), but it's the trail of dried slime left there by some slugs who have clearly been getting frisky during the night.  I know... the words 'frisky' and 'slug' don't really go together, perhaps I should have said 'horny'? - but that doesn't sound quite right either...

The great grey/leopard slug (Limax Maximus) has quite a spectacular and complex mating ritual which involves much, well, I suppose you'd call it foreplay, as these humble but apparently very well-endowed hermaphrodites slowly circle and lick eachother for hours before doing the deed, closely entwined and suspended from a trail of slime (I wish there was a better word for that).

Catching the light in the way you can perhaps see it here, this evidence of their nocturnal dance is full of beautiful rainbow colours, like the surface of a pool of oil.  In fact, now dry and completely unslimy, it resembles a fine layer of mother-of-pearl.   They might have made a mess of the fence but I can't help but see pictures in it and appropriately enough, perhaps, they seem a bit saucy to me.  I bet you'll never look at a slug in quite the same way again.