Asynchrony in Insect Host-Parasite Interaction and its Effect on Stability, Studied by a Simulation Model

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Abstract
The model is based on a natural host-parasite system, the tortricid Epinotia tedella Cl. and its dominant parasite Pimplopterus dubius Hlmg. Field data on hatching, emergence and activity are used in the description of the frequency of susceptible hosts and searching parasites throughout the generations. Random search by the parasites was adopted for the daily events, but not for the generation as a whole. Moderate asynchrony, expressed as relative displacement of the temporal frequency curves for host and parasite, leads to stability; the model predicts instability when the populations are synchronized and when asynchrony becomes extreme. Asynchrony leads to curvilinear relationships between the calculated log a (apparent area of discovery) and log P (parasite density) without assuming mutual interference between parasites. A majority of the observed log a/log P relationships described in the literature are results of asynchrony, spatial incoincidence and aggregative behavior, and not of any significant mutual interference. The initial densities of host and parasite were important only in the vicinity of the limits between regions of stability and instability. The present system, as well as other host-parasite systems, may be described by a simple, predictive and non-explanatory model either through an apparent log a/log P relation or through an exploitation submodel using a negative binomial distribution. [The study of insect host-parasite interactions is due to an increased interest in biological control.].

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