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Why Do Insects Have Gay Sex?

A new study gets to the bottom of same-sex insect love.
14.11.13

Photo by Vvillamon, via Flickr

For centuries naturalists have observed and recorded homosexual behaviour in nature. Famed explorer George Murray Levick was so shocked by the “astonishing depravity” of the male Adélie penguins he observed on the 1910-13 Scott Antarctic Expedition that he successfully hid his research notebook from the public for 100 years. The recently unearthed document detailed such acts as penguin-on-penguin rape, chick molestation and displays of gruesome necrophilia, as well as widespread homosexual relations among birds that the disgusted adventurer, discarding all impartiality, called “hooligan males”.

Annons

Although cultural biases have long obscured observation of “deviant” acts in nature, a spate of recent studies have established that a wide spectrum of species engages in non-reproductive sexual behaviour. As the evidence mounts that same-sex sexytime is a common occurrence in the animal kingdom, scientists have come up with a variety of explanations for why going “gay” might be an evolutionarily advantageous trait, despite the fact that doing so cannot result in baby making. Some scientists have posited that non-reproductive orgasm is a way to keep sperm stocks fresh; some guess that animals need the practice; some observe that same-sex sexual (SSS) activity strengthens social bonds or establishes hierarchal structure; and others suggest that animals just wanna have fun.

A new study suggests that the reason same-sex copulation is so prevalent among insects – under lab observation up to 85 percent of male bugs bone other males – might just be that they can’t tell each other apart. Scientists have seen the same phenomenon in bugs in the wild, too. In a recent paper published in the scientific journal Behavioural Ecology and Sociobiology, biologists Inon Scharf of Tel Aviv University and Oliver Martin of ETH Zurich tackle the “evolutionary paradox” of SSS behaviour, noting that while its “costs seem obvious, positive contributions to fitness remain unclear.”

After analysing studies that document the sex life of 110 different species of insects and arachnids, the researchers say they can find no proof that bugs practice intentional “gay” behaviour. They conclude that SSS activity occurs because bugs are horny as fuck and can’t be bothered to spend the time or energy to discern the sex of their object of affection. They haven’t evolved the sense to tell the difference between a viable mate and some dude who’s been recently dosed by female pheromones, or a female that’s a different species altogether, or even inanimate objects (the lusty Australian jewel beetle has been known to copulate with alluring brown beer bottles).

Annons

This “fuck anything that moves” (or doesn’t move) tactic, say Scharf and Martin, is useful because the more insects do it, regardless of who they do it with, the more likely it is that they will spread their genetic material to the greatest number of fertile females. Scharf and Martin write that there is no proof that this willy-nilly boning strategy is part of any homosexual desire. Rather it is the result of a simple calculation: “The cost of rejecting a valid opportunity to mate with a female is greater than that of mistakenly mating with a male.”

I spoke to Inon Scharf over email about bug libido, comparative zoology, and how much it sucks to be a mistaken object of affection.

VICE: Why wouldn’t insects have evolved a better sense for telling the sexes apart? Is there an adaptive advantage to that kind of “you’ll probably do” mentality?
Inon Scharf: This reminds me of a funny saying: “It's better to be rich and healthy than sick and poor.” Of course, it will be better to distinguish 100 percent between the sexes and avoid homosexual mating (if we accept our suggestion that it is a mistake indeed), while paying no costs. However, animals are not perfect, and there are many types of trade-off in nature. Let’s refer to the speed versus accuracy trade-off. Fast decisions increase the chance of mistake. It would be better to decide both fast and accurate, but this does not usually happen. Sometimes fast decisions are much more helpful than slow though accurate decisions. This could be also the case here. Let’s think of two males. One is 100 percent accurate with his mate choices (he chooses only females), but the other does some mistakes but is faster. In the case of strong competition, the male choosing fast and inaccurate could be much more successful. Such trade-offs are assumed to enhance variation in nature.

Annons

What are the benefits of doing a cross-species comparison of this kind of behaviour? Don’t many of the insects mentioned in the various studies have vastly different anatomies and behaviours? How consistent is insect sexuality across species in general?
This is a good point, which can be asked about any comparative scientific work. On one hand, you are of course right – each system is unique and has its own characteristics. But on the other hand, one important goal of science is to reach a better understanding of life, and this could be done by comparing studies and species, and looking for the common things (while also considering the uniqueness of each system). In short, generalisations are very important in biology, even at the expense of accuracy.

What about the male bugs who are getting penetrated by another male? Are there any drawbacks for the male insects that are mistaken for females and mounted?
Yes, although not much is known. First, they lose time, which could be devoted for other activities (such as mating themselves with females). This is especially important if life in general is short or if there's a short “time slot” for mating. Second, because there is no genital fit or because they tend to resist this mating, they can get injured. Third, they can get infected with some sex disease, while not getting any benefit (transmitting their sperm to a female).

@roseolm

More on sex in the animal kingdom:

The Woman Who Trains Dogs to Have Sex With Humans

Animal Penises Are Super Weird, You Guys

It It Weird When Pets Watch You Have Sex?