This Is Why Spider Monogamy Is Terrifying

Where would I be without regular spider reports? Meanwhile, I noticed an uptick of moths in my house. Spiderbro is getting complacent! Time to get out the vacuum . . ..

Soyeun Choi
1:56 PM Jun 19 2013

How to make something dirty sound scientific:

Whatever the case, if a male dies after only mating with a single female, it's an example of monogyny, which is relatively rare, having been found in a few other spiders, insects and fish (such as the anglerfish). In the animal kingdom, males will typically mate with as many females as possible; females will also mate with multiple partners, but they are pickier with their mates. In other cases, males will mate less frequently than expected because they instead invest more energy into child rearing.

These different strategies carry their own reproductive benefits to the male, whether that is more offspring or healthier offspring. However, evolutionary biologists have struggled to find similar benefits to monogyny, where males will not only mate with a single female, but also forgo any child rearing, Schwartz says.

According to theory, male monogamy is most likely to develop in species with a male-biased effective sex ratio — the ratio between adult males and females that mate at least once. In these cases, where there are a lot more sexually mature males than females, males should want to focus their energy on a single, virgin female and fertilize all of her eggs, instead of trying to fertilize the eggs of multiple other females. The model also predicts that this male-biased sex ratio is more likely to occur in species with a female-biased sexual dimorphism (females are larger than males) because smaller animals have a better chance at surviving to breeding age.

I see, so if we kill a guy after sex, that dude cannot have sex with others, and therefore he's monogamous.

Which is the way of the world for some fish and bugs. (a/k/a our food and our food's food.)

It's the circle of life.

How to make something dirty sound scientific:

<blockquote>Whatever the case, if a male dies after only mating with a single female, it's an example of monogyny, which is relatively rare, having been found in a few other spiders, insects and fish (such as the <a rel="nofollow" target="_blank" href="http://io9.com/5971912/true-facts-about-the-angler-fish">anglerfish</a>). In the animal kingdom, males will typically mate with as many females as possible; females will also mate with multiple partners, but they are pickier with their mates. In other cases, males will mate less frequently than expected because they instead invest more energy into child rearing.

These different strategies carry their own reproductive benefits to the male, whether that is more offspring or healthier offspring. However, evolutionary biologists have struggled to find similar benefits to monogyny, where males will not only mate with a single female, but also forgo any child rearing, Schwartz says.

<a rel="nofollow" target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed/16153026">According to theory</a>, male monogamy is most likely to develop in species with a male-biased effective sex ratio — the ratio between adult males and females that mate at least once. In these cases, where there are a lot more sexually mature males than females, males should want to focus their energy on a single, virgin female and fertilize all of her eggs, instead of trying to fertilize the eggs of multiple other females. The model also predicts that this male-biased sex ratio is more likely to occur in species with a female-biased sexual dimorphism (females are larger than males) because smaller animals have a better chance at surviving to breeding age.</blockquote>

I see, so if we kill a guy after sex, that dude cannot have sex with others, and therefore he's monogamous.

Which is the way of the world for some fish and bugs. (a/k/a our food and our food's food.)

It's the circle of life.

Adam Rifkin
2:20 PM Jun 19 2013

Hey, hey there: no one has to kill anyone. In this case, they just die! Pretty chivalrous, imho. Ha ha. KIDDING.

PS There are many instances when the female dies to feed her young so basically: blame the kids.

Soyeun Choi
2:29 PM Jun 19 2013

Wow, children really do take a lot out of us.

Adam Rifkin
4:47 PM Jun 19 2013

Just to get through it I had to read the article with a German accent.

<It is common among spiders, male dark fishing spiders begin by ejaculating onto a "sperm-web." They then suck up the sperm with their two pedipalps (sperm-transfer appendages). To mate, the male will insert one of his pedipalps into a female's genital opening, and the hematodochal bulb inside the appendage will expand to push sperm into the female. The researchers saw that the males' legs curled up underneath their bodies and they hung motionlessly from the female's genital opening after the bulb expanded.

Tests showed that the males' heartbeats stopped within a few hours — even if the females didn't cannibalize their mates while they hung inert, the males would die anyway.

Schwartz says that the bulb inflation likely has something to do with the males' spontaneous deaths. "We have a number of different, weird observations," he says. In other spider species, the males' pedipalps contract after transferring sperm. But the bulbs of each and every one of the male D. tenebrosus remained swelled, representing a form of genital mutilation. What's more, "every single male that has mated died in the same way," Schwartz adds.

In fact, even males that did not actually have sex died after their pedipalps expanded. Schwartz recalls several males whose bulbs swelled and died just from him handling them. In another case, a male expanded onto a female's leg and subsequently died. Given that males always die after sex, this means that they only mate with a single female — they're monogamous.>

Just to get through it I had to read the article with a German accent.

<It is common among spiders, male dark fishing spiders begin by ejaculating onto a "sperm-web." They then suck up the sperm with their two pedipalps (sperm-transfer appendages). To mate, the male will insert one of his pedipalps into a female's genital opening, and the hematodochal bulb inside the appendage will expand to push sperm into the female. The researchers saw that the males' legs curled up underneath their bodies and they hung motionlessly from the female's genital opening after the bulb expanded.

Tests showed that the males' heartbeats stopped within a few hours — even if the females didn't cannibalize their mates while they hung inert, the males would die anyway.

Schwartz says that the bulb inflation likely has something to do with the males' spontaneous deaths. "We have a number of different, weird observations," he says. In other spider species, the males' pedipalps contract after transferring sperm. But the bulbs of each and every one of the male D. tenebrosus remained swelled, representing a form of genital mutilation. What's more, "every single male that has mated died in the same way," Schwartz adds.

In fact, even males that did not actually have sex died after their pedipalps expanded. Schwartz recalls several males whose bulbs swelled and died just from him handling them. In another case, a male expanded onto a female's leg and subsequently died. Given that males always die after sex, this means that they only mate with a single female — they're monogamous.>

Geege Schuman
2:16 PM Jun 19 2013

I appreciate that little bit of direction! It is like a desperate plan from an inept villain.

By the way, how powerful is the urge to procreate when the little guy is dropped into a sterile, foreign bucket with a female he only just met and he STILL wants to have sex? Every spider I have ever captured (in jars with tightened lids) only ever looks for a way out.

Soyeun Choi
2:32 PM Jun 19 2013

No comment. Seriously, no comment.

Geege Schuman
2:37 PM Jun 19 2013

I believe Oprah said it best when she said...