Sex on Six Legs: Lessons on Life, Love and Language from the Insect World

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Sex on Six Legs:
Lessons on life, love and language from the insect world
Marlene Zuk • Houghton Mifflin Harcourt, New York, 2011.
Sex on Six Legs: Lessons on life, love and language from the insect world, by Marlene Zuk

To most of us, the instinctive response to insects is to swat, spray, scratch and swear. But to Marlene Zuk, a professor of biology at the University of California at Riverside, insects in all their astonishing diversity are the prime lens for examining biology and evolution. With six legs, tiny brains, chitinous external skeletons and countless adaptations to niches within niches in the environment, you’d think insects would have invented just about every sexual and “child”-raising oddity imaginable.

You’d be half-right, but insects have also invented some unimaginable oddities, including a number of ferocious sperm-competition routines, and our favorite: “Making a meal of mother.”

The average insect lays eggs and hits the road, but momma earwigs are devoted guards of her developing eggs. And no, earwigs do not crawl into the ear.

We may call parental care “love,” but Zuk calls it “a smart investment.” If a mother burrower bug did not tend them, her eggs would succumb to fungus or predators. What looks like love is actually a tool for ensuring that the genes survive to the next generation.

Indeed, it’s Zuk’s emphasis on evolution to explain the bizarre range of structures and behaviors in the insect kingdom that elevates her book from a source of prurient entertainment into a larger lesson in biology. Insects, she writes, “make us see that our way of life is not the only one – and I don’t mean that we could be eating dung [It’s the law: every insect book must mention dung beetles!] instead of cheeseburgers. I mean that it is possible to be unselfish without a moral code, sophisticated without an education, and beautiful wearing your skeleton on the outside.”

Many of these traits appear in a caterpillar that, having been implanted with the eggs of a parasitic wasp, continues to assist the deadly young parasites after they have moved to a nearby plant: “The ravaged caterpillar stands guard over the developing wasps and defends them against intruders with vigorous swings of its body; a most uncaterpillar-like behavior. Apparently the wasps exert a kind of mind control over their host that persists even after they leave it, doomed to die before it will ever become a moth.”

Call it a zombie, and shed a tear for the lost potential…

The book is not without problems: Zuk implies that corn is pollinated by insects rather than wind. She also offers a confused discussion of bees that learn to “recognize” human faces: “This is not suggesting that the bees actually know what they are looking at, but later on the page she discusses the implications of “the bees’ capacity to learn to recognize human faces.”

To bee honest, you can’t have it both ways…

Despite the clever title, not all of the fun concerns sex and its consequences. For example, in the chapter titled, “If you’re so smart, why aren’t you rich?” Zuk covers an experiment that successfully enhanced fruit fly intelligence, in the all-important realm of food choice. After just 20 generations, the learning curve was cut by two-thirds, but there’s a big downside: Smarter females laid fewer eggs, and braniac flies died before the wilder dimwits.

It’s as fundamental a lesson as biology will ever offer: To everything, there is a season — and penalty. No silver lining is complete without a dark cloud.

– David J. Tenenbaum