THE ECOLOGY, BEHAVIOR, AND EVOLUTION OF PERIODICAL CICADAS

Periodical cicada nymphs feed underground on root xylem fluids for pre cisely 13 or 17 years before emerging at any given locality synchronou sly and in tremendous numbers. Populations throughout the eastern Unit ed States are grouped into variously sized, geographically contiguous broods, which are reproductively isolated from each other. Six distinc t species represent the 13- and 17-year life cycle forms of three morp hologically and behaviorally distinct periodical cicadas. Recent work supports and modifies previous hypotheses concerning periodical cicada intra- and interspecific interactions, movement patterns, juvenile de velopment rates, life-cycle switching, the evolution of periodicity,an d the origination of broods and species. Major ecological interactions of periodical cicadas include infection by a host-specific fungal pat hogen, satiation of predators, and damage to hostplants. Central to th e evolution of periodical cicadas are four-year accelerations in devel opment that sometimes result in switching between 13- and 17-year life cycles.