Larvae of the turnip sawfly Athalia rosaeare chemically defended against predators such as tree frog. A naive tree frog will pick up the sawfly larva with its tongue and bring it into its mouth. The sawfly releases hemolymph, both toxic and foul tasting into the tree frog’s mouth. The tree frog will immediately spit out the larva and look for something else.
Tree frog routinely feed on undefended caterpillars of the cabbage white butterfly. The potent defense gives them a competitive edge.
Satoru Matsubara & Shinji Sugiura. Chemical defence of turnip sawfly larvae against Japanese tree frogs. Journal of Asia-Pacific Entomology. Volume 20, Issue 1, March 2017, Pages 225–227