The US Food and Drug Administration (FDA) warned on Wednesday individuals who have seafood allergies against eating cicadas, the bugs that have swarmed across a quarter of the country.

Cicadas have not been put on some dinner tables, but have also popped up on menus at select restaurants where daring customers can sample them in multiple forms, including as a taco filling and chocolate-covered treat.

Still, the FDA is warning potential consumers against doing so if they have seafood allergies, because the bugs share genetic relations with shellfish.

"Yep! We have to say it!" the agency said on Twitter. "Don't eat #cicadas if you're allergic to seafood as these insects share a family relation to shrimp and lobsters."

The Brood X tsunami of the little insects have been spotted as far south as Georgia and as far north as New York. They have also emerged in the Midwest where they have been seen in parts of Illinois and Indiana.

In the US capital region, the bugs have erupted en masse with nearly all trees and shrubs sporting a handful or more of the black and yellow insets or their shedded shells.

Estimates vary on the number of cicadas in Brood X, but they are widely believed to number in the trillions./aa