GoKawiilJune 27th, the hottest day ever recorded in Berlin, where I live, began with a whimper. My apartment does not have air-conditioning, and neither does a friend’s garden cottage where I took refuge, so my poor, panting greyhound was audibly distressed. I walked her to a park to cool off. At the entrance, I passed a sign that warned of the presence of Eichenprozessionsspinner, caterpillars with stinging hairs that German news outlets have called a “citywide plague.” The government was hiring workers in protective suits to vacuum them up. I wasn’t too worried, though. Germans often overreact to animal nuisances with complicated schemes. Who else would try to clean nature with a Hoover?
The oak processionary caterpillar, as it is known in English, is a squiggle of dark skin covered in wiry white hairs that look like the whiskers on a witch’s warts. But you never see just one caterpillar. Oak processionary caterpillars live with hundreds or thousands of their siblings, and together they look more like a wizard’s beard. The caterpillars move in a single-file line—a procession—and often defoliate oak trees completely. I saw no bare branches or caterpillars in the wooded area where my dog and I found shelter. We cowered in the shade as the temperature rose to a hundred and four degrees.
As I soon learned, you don’t need to touch these caterpillars to experience their sting. The next morning, a galaxy of itchy red bumps and blotches stretched from my shoulder to my hip. Oak processionary caterpillars have not only tufts of visible hairs but also eight hundred thousand microscopic hairs that, according to one study, can be “projected in the air as a fine powder” when a caterpillar is threatened. These hairs are toxic, and they can travel several hundred metres, survive for years on surfaces, and pass through clothing to impale skin. The entomologist Justin O. Schmidt once developed a scale for the pain inflicted by insects, describing a particularly excruciating wasp sting like so: “Torture. You are chained in the flow of an active volcano.” On a scale for itchiness, my Eichenprozessionsspinner rash would outrank all the mosquitoes, spiders, fleas, and midges that had ever bitten into my flesh. I was reminded of bedbug bites that I once suffered on a forearm, after going to a movie theatre in New York City—but the caterpillar stings covered half my body.
The heat wave broke, but the itching lasted another week. I slathered myself in ointments, even after reading a study that said treatment “shows scarce efficacy” for my condition. The main consolation I took from the scientific literature was that it could have been worse. A caterpillar hair in the eyeball can create a crusty yellow nodule that requires professional removal. In some cases, inhaling the hairs may make it difficult to breathe. Guests at a nineteenth-century dinner party suffered “a disgusting, unbearable itching and scratching in the throat” after they feasted on roasted cuckoos that had preyed on Eichenprozessionsspinner. Worst of all was the plight of a forty-six-year-old Italian farm worker who apparently masturbated after handling processionary-caterpillar nests, as described in an old dermatological case study. The scarring from his injuries was so severe that he needed to be circumcised.