Red swamp crayfish—also known as Louisiana crawfish—have a long tradition as a tasty Cajun meal, and they may feel right at home on your plate. But delicious or not, they certainly don’t belong in southern California, or the many other places around the world where they’ve become an invasive species. Now new research shows they may be dangerous for people too, as their occupation of waterways allows mosquitoes to thrive, likely increasing the risk of mosquito-borne diseases.

Red swamp crayfish (Procambarus clarkii) are native to the murky marshes of the southeastern U.S. but have now been introduced to every continent except Australia and Antarctica, instigating ecological turmoil and threatening native species, while also carrying