Finding a mate can be exhausting—so much that some animals die after finally meeting that special someone.

For Weird Animal Question of the Week, we took a closer look at the reproductive strategy called semelparity, or suicidal reproduction, in which animals concentrate all their reproductive energies into one bout of mating before death.

The poster child for this phenomenon is the male antechinus, a tiny, short-lived Australian mammal. The critter goes on a mad mating spree (sometimes as long as 14 hours), after which it suffers a fatal immune system breakdown and dies a ragged wreck. (Read more about why some animals mate themselves to death.)

You could call it a parental sacrifice: Antechinus males die knowing they'd spread their sperm far and wide.

“The trade-off is that semelparous species produce more offspring,” says Jeyaraney Kathirithamby, an entomologist at Oxford University.

One Twisted Parasite

View Images A female parasite of the Caenocholax-Strepsiptera genus is burrowed in a cricket. She'll mate, give birth, and then die here. Photograph by Jeyaraney Kathirithamby

For example, in twisted-wing parasites of the order Strepsiptera, females produce between 1,000 and 750,000 larvae in their one and only mating session.

These animals have odd lifestyles: Females bury their bodies into a host, such as a solitary bee, and never leave. With no need for wings, eyes, legs, or antennae, the females retain juvenile traits, making them look like mini marshmallows.

The only part of their body that protrudes from the host is the brood canal, an opening through which males inseminate the female and larvae crawl to the outside world. (Related: "Tough Love: Male Parasite Stabs Female in Neck With Penis.")

Males, which live up to six hours, fly around looking for these embedded females, with which they'll mate and then die, Kathirithamby says. After the larvae emerge from the female, she dies too.

Mysterious Eel Mating

Fish are famously fertile egg producers.

Pacific salmon die after spawning—the chinook species, for instance, lays up to 5,000 eggs.

American eels can produce up to 30 million eggs at a time, but their sex lives are still a mystery, notes John Casselman, a professor at Queen’s University in Ontario, Canada.

These eels can take up to 20 years to mature, upon which they'll swim toward the Sargasso Sea. Though scientists haven't observed spawning, which they're thought to do at great depths, they have recorded pulses of eel larvae coming from that direction.

View Images This pair of praying mantids will die soon after reproducing. Occasionally, the female will cannibalize the male by biting off his head. Photograph by George Grall, Nat Geo Image Collection

Sacrificial Spiders

Female spiders often get a bad rap as femme fatales that eat their mates, but mother Stegodyphus lineatus spiders die for their young.

After her first batch of eggs hatch, “mothers first regurgitate food for newly emerged spiderlings and then let the spiderlings eat her,” says Catherine Scott, a Ph.D. student at the University of Toronto in Scarborough.

Other male spiders sacrifice their bodies—literally—to make sure they're the father.

Mother-Eating Spiders Young spiderlings attack and eat their mother for survival.

Male spiders “have two sperm-transfer organs, called pedipalps,” which they insert one after the other in the females’ two sperm storage areas, Scott says. Male orb weavers of the Argiope genus die upon inserting that second pedipalp.

After death, “the male’s body hangs from the female’s genital opening,” so other males have a tough time mating with that female.

Male Argiope often mate with females who have just molted, and therefore can’t eat them. But if it’s an older female, “she will eat him shortly after he dies,” Scott says.

Well, it’s healthier than a post-coital cigarette.