Comparisons of Parasitism and Densities of Parlatoria oleae (1952-1982) in Relation to Ecological Theory

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Abstract
Analyses of data from 1952 to 1982 on the parasitism of olive parlatoria scale in California by two aphelinid parasitoids, Aphytis paramaculicornis and Coccophagoides utilis, are significant to lecological theory. Only limited time-set data support a contention of behavioral density dependence for Aphytis alone, but much data fail to support behavioral density dependence. On the contrary, analyses of data comparing the early years of high host densities with the later years of low densities caused by parasitoid action show a long-term density-dependent performance by Aphytis through the combined effects of the behavioral (functional) and reproductive (numerical) responses. Although the data show an inverse density-dependent response for C. utilis, the net effect of the two species combined was also density-dependent; thus, Aphytis offset the contrary effect of Coccophagoides. The high degree of biological control depends strongly, however, on the combined supplementary actions of the two species.