Chemical analysis of squirt-gun defense in Bursera and counterdefense by chrysomelid beetles

The genus Bursera produces resin stored in canals in the leaf. When leaves are damaged, some, but not all, species release abundant resin. Species of Blepharida are specialized herbivores of Bursera, and they exhibit variatio n in their counterdefensive behavior. Species feeding on resin-releasing pl ants cut the leaf veins before feeding, which often makes them more prone t o predation. They also adorn their backs with their feces and may regurgita te and release an anal secretion when attacked or disturbed by predators. S pecies that feed on Bursera species that release no fluids do not sever the leaf veins prior to feeding, and they do not carry their feces on their ba cks. Instead, they face their predators, raise their heads in a "boxing-lik e" display, and rapidly swing their abdomens from side to side. We performe d a comparative chemical analysis of the compounds found in Bursera schlech tendalii, a species that releases abundant resins, and B. biflora, a specie s that does not. We also analyzed the frass, enteric discharges. and larvae of the two species of Blepharida that feed on each of these plants. The co mpounds found in the body, feces, and discharges of the Blepharida species that adorns itself with feces match the chemical mixture of its host plant, suggesting that this beetle species can compensate its higher risk of pred ation by using the compounds present in the plant for defense. The chemical mixture of B. biflora is more complex and does not match the compounds fou nd in the body or frass of its beetle herbivore, suggesting that the defens ive strategy of this insect is behavioral and does not rely on its host's c onstituents.