[NSFL]

Some of the most remarkable behaviours and structures observed in mating.

Suicidal Males When Australian red-back spiders mate, the male does a somersault after inserting his penis-like organ. The somersault behaviour places his dorsal surface in front of the female's mouthparts. The female then eats the male. Experiments have shown that suicidal males copulate longer and fertilize more eggs than do males that survive copulation, probably because sperm transfer continues until the meal is over.

Giant sperm In the fruit fly Drosophila bifuca, males average 1.5 mm in total body length. Their sperm, however, are each 6 cm long. Recent research suggests that the coiled sperm fill the female's sperm storage area and prevents competition.

Having an affair Researchers who use genetic markers to assess paternity in birds that appear to be monogamous find that up to 60% of nests contain at least one offspring fathered by a male that is not mated to the resident female. In most cases, "infidelity" occurs because females actively solicit copulations from males holding nearby territories.

Love darts Many snails and slugs are hermaphroditic, meaning an individual has both male and female gonads. During mating, 2 individuals simultaneously receive and deposit sperm to fertilize each other's eggs. In some species, individuals fire "love darts" of unknown function from their genitalia into the mater partner. In other species, the penis frequently becomes stuck in the female reproductive tract and is bitten off by one partner.

Hypodermic insemination Some bedbugs have hypodermic penises. Males force the organ through the female's abdominal wall and deposit sperm directly into her body cavity.