Responses of Invertebrate Herbivores to Stinging Trichomes of Urtica dioica and Laportea canadensis

Abstract

We investigated whether stinging trichomes of two plant species, Urtica dioica and Laportea canadensis, are effective defenses against four species of invertebrate herbivores (Vanessa atalanta, Popillia japonica, Chortophaga viridifasciata and Anguispira alternata). Feeding was compared on leaf pieces of contrasting stinging trichome density, in petri-dish feeding trials. In addition, a test of snail movement over hairy and shaved L. canadensis stems was carried out. In no case was there significant evidence that stinging trichomes deter or interfere with feeding by these herbivores. Factors of body size and feeding behavior allow them to feed with little interference from nettle stings. Stinging trichomes are known to be effective against mammalian herbivores, and are well-suited to deterrence of large grazers. We therefore hypothesize that stinging has evolved as a defense against mammalian herbivory.