As regulars to my Flickr collection may have noticed, I've developed a bit of a penchant for invertebrate NC-17 moments, especially amongst ladybird beetles (née ladybugs). I find the black bean aphids (Aphis fabae) a charming touch to this shot of asian ladybird (Harmonia axyridis) relations. One is tempted to analogize to pair of humans coupling on a counter at Denny's amidst a pile of grand slam specials. Or at least I am tempted to draw that comparison.
You'll also note that this photo has a good view of the male's aedeagus. Sperm delivery organs have evolved independently within many animal lineages: there is the infamous "tentacle sex" of cephalopods, the gonopodium of certain live-bearing fish species, the double-trouble hemipenes of snakes and lizards and the impressively lengthy duck phallus (not to mention similar structures known in annelids, gastropods and, of course, mammals).
Indeed, evolution has had a ball with genitalia (weak pun not intended), and for good reason: sex and reproduction are at the core of the struggle for existence. Evolution is so picky with penes that penile morphology is often used as a key method for sussing out phylogenetic relationships in such diverse groups as flies and primates. Here's an interesting paper on the influence of contrasting selection pressures on the morphology of the male member in a group of tropical fish. In this case males cope with the perpetual struggle of attracting potential mates while trying to avoid attracting predators.
What would quality porn be without another angle?
For those of you more inclined to read your erotica, here's an account of ladybird reproduction courtesy of the Ladybuglady.
Once a male has found a female to mate with, he will grasp her firmly from behind using the front most part of the leg, called the tarsi. The tarsi is like a serrated claw with sticky pads. This allows the male to get a stable grip of the female during copulation. In this position, it looks as though one is getting a "piggy-back" ride. The male's genetic material is passed to the female through an ejaculatory gland, much like an oviposititor for the female. The male's genetic material than passes into the female through the oviduct to the spermatheca. This is a special sac in the female's body where the sperm can be stored for up to several months before it is used to fertilize the eggs as they are laid.
One thing I've noticed about the beetles in our garden is that copulation seems to take a long time for such small critters. I've seen pairs carry on happily for hours. All that love-making must do wonders for the appetite:
This is actually a shot of a seven-spotted ladybird (Coccinella septempunctata) which, like the asian ladybird, has been introduced to our area as a pest control agent.
Those of you craving more graphic invertebrata should check out this post on Snails Tales, which answers the age-old question "who would win in a cage match between a garden slug and an earth worm?" (hint it's the one with a radula). If you've recently gorged yourself, I suggest you wait a bit for it to settle before heading over there.