Boomeranging in structural defense: phytophagous insect uses cycad trichomes to defend against entomophagy.

Plant defensive behaviors that resist arthropod herbivory include trichome-mediated defenses, and variation in plant trichome morphology and abundance provides examples of the mechanistic complexities of insect-plant interactions. Trichomes were removed from Cycas revoluta cataphylls on the island of Guam to reveal Aulacaspis yasumatsui scale infestation, and predation of the newly exposed insects by pre-existing Rhyzobius lophanthae beetles commenced within one day. The quotient of predated/total scale insects was 0.5 by day 4 and stabilized at that found on adjacent glabrous leaves in about one week. The trichome phenotype covering the C. revoluta cataphyll complex offers the invasive A. yasumatsui armored scale effectual enemy-free space in this system. This pest and predator share no known evolutionary history with C. revoluta, therefore, the adaptive significance of this plant behavior in natural habitat is not yet known.