In addition to the catastrophic flooding from Hurricane Harvey, Houston residents have one more thing to worry about: floating colonies of fire ants.

Fire ants have waxy bodies that allow them to repel water. Should a colony find itself waterlogged, ants will protect their queen by forming a mass around her, as well as eggs, larvae, and pupae (ants that are in between larvae and adults). As the ants float, they rotate, so that the underwater ants will get to the top and vice versa. This behavior is totally normal, Molly Keck, an entomologist at Texas A&M AgriLife Extension Service, tells The Verge. "We usually call fire ants flood water species,” she says. “They've been known well before this hurricane to float on top of water like that.”

Pro tip: Don't touch the floating fire ant colonies. They will ruin your day. #Harvey pic.twitter.com/uwJd0rA7qB — Mike Hixenbaugh (@Mike_Hixenbaugh) August 27, 2017

Keck describes these clumps as “chain-link ants.” They hook their feet and hang onto one another to preserve their colony while flooded. “When the water recedes, or they float to a spot where they hit dry land, then they'll build their colony again in their spot,” Keck says. In a flood, this can be particularly scary if they choose to board a temporary sanctuary someone has taken refuge on — like a roof.

The ants, in fact, aren’t harmless, she says. People who come in contact with the colonies will get at least a few itchy, probably painful pustules. But how your skin reacts can differ from swelling to life-threatening allergic reactions. “Once they hit you, you're a solid surface so they're gonna crawl on you,” Keck says. “When the first one stings, they emit a pheromone that causes a chain reaction that tells everybody else to sting, so you're going to experience quite a few stings.” The best thing to do is to rub them off as quickly as possible. “They'll kind of roll up when you brush against them, and so that's an easy way to try and get them to detach from you,” she says.

Those looking to go on the offensive may want to spray the ants with dish soap to break down their waxy rafts, according to Wired. Of course, that means getting close to the adrift colony, which Larry Gilbert, a professor of integrated biology at the University of Texas at Austin, strongly advises against. “You protect yourself by avoiding them, not by messing with them,” he says. "They don't come to attack you. They're just passively floating along. It's a matter of being just intelligent and evasive.”

Meanwhile, in Cuero, the river has brought my aunt all of the fire ants. Yes, those are all (of the) fire ants. pic.twitter.com/dEibWYxAdl — Bill O'Zimmermann (@The_Reliant) August 29, 2017

But if you find yourself unable to escape their path, Keck suggests creating waves to wash them away from you. “They are pretty well globbed up, and so if you're quick enough, you can kind of move them a few inches away from you so you can avoid them,” Keck says. At the very least, their distinctive rust coloring makes them easy to spot for what they are and not a piece of debris.

Keck says there’s no danger of them spreading beyond states they already inhabit. That might not be comforting for those in Texas and Louisiana, but at least the fire ants are not building wriggling Eiffel towers. Yet.