Numerical response of a parasitic mite: Host effect and mechanism

Populations of the mite Hemisarcoptes coccophagus Meyer parasitizing 2 species of armored scale insects were sampled during 1 yr in Israel. Oleander scale, Aspidioutus nerii Bouche, occurred on leaves, and latania scale, Hemiberlesia lataniae (Signoret), inhabited leaves and branches of acacia, Acacia cyanophylla Lindley. We applied regression analysis to explore effects of different host stages, age phases, and species on the numerical responses of the mite to changing scale densities. Our data demonstrate the existence of host-specific numerical responses. The mite responded faster to the density of latania scale than to the density of oleander scale. The numerical responses were faster for ovipositing scale females than for young females. The strength of mite response to the density of the various scale stages, phases, and species was correlated positively with their suitability for the mite. The numerical response of the mite to changes in its host density acted mainly through aggregation or improved survival rather than by enhanced fecundity.