IS THE CHEMICAL DEFENSE OF EURYCOTIS FLORIDANA A DETERRENT TO SMALL MAMMAL PREDATORS?

Adults of the subtropical cockroach Eurycotis fioridana emit a defensive chemical spray from their abdomens consisting primarily of (E)-2-hexenaI. Nymphs are similar in size to the adults, but lack the chemical defense. The ability of the defensive spray to repel predators has received relatively little study. We conducted feeding trials with two species of mice, Peromyscus gossypinus and P. polionotus, that are abundant in the natural habitats that support Eurycotis in central Florida, and potentially important predators on Eurycotis. We offered Eurycotis nymphs and adults to captive mice and recorded compared handling times among trials. Both species of mice were adept at handling nymphs but were visibly distressed when exposed to (E)-2-hexenal. Peromyscus polionotus proved largely unable to handle adult Eurycotis because of the inability of this mouse to deal with the chemical defense. In contrast, P. gossypinus dealt well with adult Eurycotis by thrusting the roach's abdomen into the substrate and feeding from the head end to avoid exposure to the chemical defense. We conclude that the chemical defense of Eurycotis is an effective deterrent to small mammal predators, but that at least some individuals of P. gossypinus adopt a behavior to neutralize that defense.