Longitarsus jacobaeae is a species of flea beetle known as the tansy ragwort flea beetle. It is used as an agent of biological pest control against the noxious weed known as ragwort (Senecio jacobaea). The beetle is not choosy between species in the genera in which it feeds from, and recent studies with the beetle have shown "that selection pressure by specialist herbivores is not likely a driving force in evolutionary diversification" of the plants which contain the alkaloids that the beetle dines on.