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Jul. 14, 2014

Picture of the Week: Harlequin Bug Eggs

by Becca Cudmore

Click to enlarge images
The piebald cylinders above may look like handcrafted confections, but they’re hardly sweet. These are actually insect eggs, and within two weeks, each one will release a starving, life-sucking harlequin bug nymph. When they feed in large numbers, the insects—a species of stink bug native to Central America—have been known to decimate entire fields of cabbage and collards in the United States, where they’re considered an invasive species.
 
Unlike many other stink bugs that eat only the seeds of a plant, harlequins are indiscriminate feeders. “The harlequin bug doesn’t care; they’ll just jab their big [needle-like] mouthparts into a plant wherever,” says entomologist and agricultural research scientist Deane Jorgenson. This fierce extraction method can result in scars that turn crops into grocery store discards or detritus in the field.
 
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Once a harlequin bug has penetrated a plant, it sucks its juices and steals glucosinolates—sulfur-based, toxic compounds produced by species in the mustard family. The floral chemistry arms the insect with a potent smell—hence the “stink” in stink bug—and taste, which both turn off would-be predators.
 
As if the nasty smell weren't warning enough, harlequins also advertise their putrid flavor with conspicuous markings called “aposematic coloring”—in this case, a fiery red geometric pattern that deters predators and allows the bugs to “feed out and about all day,” says Jorgenson. (Related species, like the more common brown marmorated stink bug, use camouflage to avoid predators.)
 
Perhaps fittingly, harlequin bug eggs also stand out. Although they’re pale yellow when first laid, the watertight eggs quickly turn solid white with two black bands and look like “little standing-up beer keg[s],” says Jorgenson. Above the lower band sits a single black spot, almost “like a bunghole,” she says, “where you would stick the big cork in casks of beer or whiskey.” When the nymphs are ready to hatch, the top of the egg pops off “like a Jack-in-the-box,” and the insects crawl through (Jorgenson says that researchers still don’t have an explanation for the eggs’ two-toned coloring, however.)
 
In the time-lapse video below, you can see harlequin nymphs emerge from their birth kegs—which are each about 1/16th of an inch wide—and begin to darken as their exoskeletons develop. “Some people find them creepy,” says Jorgenson, but “I think they’re pretty cute.”

About Becca Cudmore

Becca Cudmore is Science Friday's web intern and a graduate student in the Science, Health, and Environmental Reporting Program at New York University.

The views expressed are those of the author and are not necessarily those of Science Friday.

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