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Bring on the aerial ant sex

People sometimes talk about being transported on the wings of love. For fertile ants, this is a literal concept.

April 29, 2012|By Marlene Zuk
  • When the days lengthen and the earth warms, the thoughts of a select class of ants turn to passion.
When the days lengthen and the earth warms, the thoughts of a select class… (Illustration by Dugald…)

For those who think spring is all about robins arriving, or window cleaning or crocuses budding, I have two words for you: ant sex.

Now, I know what you're thinking: Those tiny black creatures marching relentlessly toward the sugar bowl or streaming across the driveway are all infertile females who have no interest in sex at all. This is true. But when the days lengthen and the earth warms, the thoughts of a select class of ants turn to passion.

An ant queen produces all of the other ants in the colony. The vast majority of them are sterile female workers, but at certain times of the year she also produces males, as well as some females capable of laying eggs themselves. These future queens and their mates have a startling characteristic not shared by other ants in the colony.

People sometimes talk about being transported on the wings of love. For fertile ants, this is a literal concept. They have a pair of transparent wings on their backs, ready to bear them up out of the gloomy passages of the nest and into the soft spring air. In some ant species, both sexes fly. In others, only the males are winged, while the would-be queens have to crawl out of the nest and send out pheromones — chemical come-hither signals — to the more widely ranging males.

The flying forms of ants are called alates, after the Latin word for wing, though the wings will be used only for the briefest of times.

I imagine the alates underground before liftoff, as nervous as any cast member backstage on opening night, fidgeting and rustling their paper-crisp wings. The so-called nuptial flights are doomed in wet or windy weather, so the insects must worry about rain. But if the conditions are right, the alates — thousands upon thousands of them — rise in clouds, flying away from the nest in search of aerial romance.

Of course, for the bulk of the alates, romance proves elusive. They are eaten by birds and other predators or fail to find a mate of the appropriate sex and species. (On the bright side, alate emergences are a bonanza for birds, which use the juicy young ants as food for their own chicks.) If two ants do manage to connect, the much-smaller male attaches himself to the female and inseminates her, whereupon his genitalia explode and he falls to the ground, lifeless. I tell my students that this outcome is the best one possible for the male, evolutionarily speaking, since his genes will live on in the queen's offspring, but they seem skeptical.

The males vie with each other for access to the virgin queens, and they can be extremely determined. The Internet recently was abuzz over a video that photographer and ant expert Alex Wild posted on his blog, and succinctly headlined: "Male ants don't particularly care if their mate is dead and being eaten by a spider." As Wild noted — and who could argue — "I can't imagine anything more unpleasant than being sucked dry by a crab spider latched to my skull. Other than the same, but simultaneously being assaulted by a sex-crazed drone swarm."

The swarms sometimes form enormous masses. In 2009, flying ants were so numerous that they interrupted a Champions Trophy cricket match in South Africa between Australia and New Zealand. The alates from multiple colonies often all emerge at once, which helps reduce inbreeding because males and females can find mates outside their own nest. This probably happens not because the ants are communicating but because they all respond to the same environmental stimuli.

What ant sex reminds us is that spring can be kind of scary, or at least sobering, particularly for non-humans. Millions of ants, millions of robin eggs, millions of flower seeds, most destined to die before they are even fully grown, and almost all unlikely to reproduce. All that rampant profligacy, all that heedless destruction. In "Pilgrim at Tinker Creek," Annie Dillard writes, "I can like it and call it birth and regeneration, or I can play the devil's advocate and call it rank fecundity — and say that it's hell that's a'poppin.'"

I don't know if it is hell, exactly, or if so, then the nether world bears a striking resemblance to, well, anyplace with a seasonal climate. Regardless, the swirling multitudes of winged ants remind us that spring may be about renewal, but it's also about going for broke, about massive overproduction — and about one sliver of time when even the most earthbound creatures can break loose and head for the sky.

Marlene Zuk is a professor of ecology, evolution and behavior at the University of Minnesota. Her latest book is "Sex on Six Legs: Lessons on Life, Love and Language From the Insect World."

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