Estimation of the stage-specific survival rate in the insect population with overlapping stages

Summary

An application ofHokyo andKiritani's method (1967) was attempted to estimate the stage specific survival rates of the population with overlapping stages. This method can be written as follows assuming a constant daily survival rate (K) throughout the life:

$$F_{\alpha _i } /F = 1 - K^{\alpha _i } $$

where,$F_{\alpha _i }$ andF refer respectively to the total incidence ofith instar nymphs and that of individuals afterith instar inclusive, andα _i refers to the developmental period ofith instar.

Application of this model to caged and natural populations of the southern green stink bug,Nezara viridula, was made to test its validity. The estimates of the initial number of successive stages obtained from the present method were compared with those fromRichards andWaloff's method (1954) for the caged populations of 1st, 2nd and 3rd generations. The superiority of the present method to theRichards andWaloff's in estimating adult numbers was shown in all the generations examined. When different daily survival rates are involved in the course of population decrease, application of the revised method proposed byHokyo andKiritani (1967), gives much reliable estimate as compared with one before correction.

The present method is useful in constructing life table of such species as scale insects which complete their life cycle within a defined space, but their successive stages overlap considerably.