Here's some gastropod porn for you. I noticed these two Red Triangle Slugs getting it on at the rear of my house this morning. We've had a couple of storms over the last few days and these slugs tend to come out after rain.
Slugs are hermaphrodites, having both male and female genitalia. These two have followed the normal Red Triangle Slug sex position (they only have one) by encircling each other and exchanging sperm through their protruded genitalia. In a few days they will lay around 30 eggs in a hole in the ground, or beneath the cover of an object such as a fallen log.
The hole you can see in the distinctive red triangle marking is a breathing pore.
These slugs feed only on algae so you don't have to worry about them eating your plants. I find them not only beautiful to look at, but also helpful to have in my yard.
I've blogged about Red Triangle Slugs in a previous post.