INTERSPECIFIC INTERACTIONS IN PHYTOPHAGOUS INSECTS - COMPETITION REEXAMINED AND RESURRECTED

This review reevaluates the importance of interspecific competition in the population biology of phytophagous insects and assesses factors t hat mediate competition. An examination of 193 pair-wise species inter actions, representing all major feeding guilds; provided information o n the occurrence, frequency, symmetry, consequences, and mechanisms of competition. Interspecific competition occurred in 76% of interaction s, was often asymmetric, and was frequent in most guilds (sap feeders, wood and stem borers, seed and fruit feeders) except free-living mand ibulate folivores. Phytophagous insects were more likely to compete if they were closely related, introduced, sessile, aggregative, fed on d iscrete resources, and fed on forbs or grasses. Interference competiti on was most frequent between mandibulate herbivores living in conceale d niches. Host plants mediated competitive interactions more frequentl y than natural enemies, physical factors, and interspecific competitio n. Sufficient experimental evidence exists to reinstate interspecific competition as a viable hypothesis warranting serious consideration in future investigations of the structure of phytophagous insect communi ties.