MODIFICATION OF THE RANDOM-SEARCH TYPE-II FUNCTIONAL-RESPONSE EQUATION FOR INCORPORATION INTO SIMULATION-MODELS

Because of the assumptions implicit in the Royama-Rogers' Type II Rand om Search Parasitoid Equation (RSPE), the estimates of parameters are valid only within an area unit equal to the experimental area used to estimate them. This assumption was tested using different values of N- t (host density) and P-t (parasitoid density), while maintaining the h ost:parasitoid ratio constant at 10:1. If the RSPE is valid at any are a unit, then the value of F(N-t,P-t) (probability of being parasitized ) should be constant at all values of N, and P, provided that the N,: P, ratio remains constant. Instead, the value of F(N-t, P-t) showed an asymptotic rise to a plateau. This result supports the assumption tha t the RSPE validity is limited by the area unit in which its parameter s are estimated. Such a limitation precludes the incorporation of this Type TT equation into an age-structured simulation model. A modificat ion to the RSPE which lacks these space-dependence limitations is prop osed. The modification consisted of the division of the coefficient d by parasitoid density (P-t). This modification transforms the instanta neous rate of discovery into a per capita basis.