strange behaviors

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  • Richard Conniff writes about behavior, in humans and other animals, on two, four, six, and eight legs, plus the occasional slither.

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Valentine’s Day Woes? It Could Be Worse.

Posted by Richard Conniff on February 13, 2009

chocolatebeetlesSo maybe your loved one’s idea of a great Valentine’s Day gift is chocolate rhinoceros beetles.  They’re being offered by a Japanese web site for roughly U.S. $49.  Consider yourself lucky.  Here’s a report about deceptive mating practices in the natural world:

Spending the day of love alone, with a carton of Ben and Jerry’s or a handle of Jack? Abandoned by your one and only just last week, right after you finished putting him/her through grad school?

Well, it could be worse. At least you haven’t been eaten alive on a blind date.

Here’s how it sometimes happens in many species of moths throughout America, Africa, and Australasia.  To start with, the females in these species send out pheromones as a chemical advertisement of sexual availability. It’s like putting a profile up on match.com. The hypersensitive male moths detect the sex pheromones with their antennae, and come flocking by the dozen, ready for action.

But moth pheromones and dating websites can both be deceptive, and some of the moths don’t have quite the dating experience they envisioned.

The problem is that bolas spiders of the genera Mastophora, Cladomelea, and Ordgarius have evolved to imitate these sex pheromones.  As the excited moths flock in, the bolas spiders detect them with their sharp eyesight and hearing–and then pluck the unlucky suitors out of the air with a sticky ball on the end of a string.

The spider pulls in the male moth and embraces it. Then the unhappy couple hang from the string and spin together in a morbid waltz while the spider wraps the moth for future consumption, and finally leaves to fish for another victim.

To add insult to injury, the spider having the moth for dinner is not even good looking. To avoid being eaten by predators itself, the spider disguises itself as a large bird dropping. That’s what I’d call a shitty date.

For more general information about the bolas spiders read:

KV, Yeargan. 1994. Biology of bolas spiders. Annual Review of Entomology
Vol. 39: 81-99
http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.en.39.010194.000501

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