By F. S. Bodenheimer (auth.)
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The elephant may serve as a theoretical example with 100 years longevity and 4 young ones on the average (m. ): Generation . . . . . . P F 1 F 2 F 8 F 4 F 5 F 6 F 7 F 8 F9 F 10 Rise of population . . . . 2 4 8 16 32 64 128 256 512 1,024 2,048 In the elephant, 10 generations extend over more than 500 years, whereas in voles over at least 16 months, in Protozoa over a day only. A particular type of restriction may still be discussed. In the beehive the number of reproducing individuals is reduced to one queen only.
The bonitation concerning the host-factor should never be made for a whole country or region, but must be determined for each locality separately. Considering the importance of its host-factor and its dependency on two major components, we express it as a fraction: host suitability host"abundance F or the final damage bonitation we now proceed as follows : the weather and generation-factors are multiplied by the sum of both host-factors, and eventually - before multiplication - the unfavourable rain-factor is deducted from the climatic factor.
4 1,218 15 19 27 45 130 33 43 59 98 287 54 60 97 160 469 Hyperbola B represents the epidemiological average of annual generations. But a few individual flies may survive for periods much longer than those given by hyperbola C, and those few survivors are of paramount importance for the maintenance of the species during unfavourable seasons, in which suitable hosts are rare or absent. The physical zones of comfort of the species are: I Zone Optimal . . H. < 72- 85 60-90 40-100 40 Bonitation index 2 l 0 0 In this way we obtain a reliable basis for climatic bonitation of C.