DYNAMICS OF FIELD POPULATION OF I"NE LOOPER
293
density of the previous year (log Lt) results in a regression coeficient of
0.38 (Fig. 38-A). If the former is plotted over the product of the latter
and the fraction of advanced larvae surviving (log Lt . sPp5 = the logarithm of nymphal density), then the coefficient iricreases to 0.52 only
(Fig. 38-B). This suggests that a good deal of density governed reactiqn
must be present in other components, and the weak density induced,
variability of fecundity alone cannot account for this.
(c) Prepupal Mortality. If the k-values of prepupal mortality (k,) are
plotted over nymphal density there proves to be 110 relation.
3. Mortality in the Pupal Stage
The results of the regression analysis shown in Fi,z. 33 and Table XXV
suggest that pupal mortality includes a weak density related factor. In
principle this can be both delayed and direct density dependent, because the mortality is partly determined by parasites operating mostly
in the preceding summer, and partly by predators (and disease), which
are especially active in the period March to June. In this section the
possible occurrence of density dependent factors hits been studied only.
The parasites are considered in a later sub-chapter.
There proves to be no relation between total pupal mortality (k,-J
and pupal December density. Nor is there any relation between the
k-value of non-parasitic mortality and pupal density. From these
results it is concluded that there is no direct density dependent effect
included in this age-interval mortality.
4. H t a l i t y in the Moth Stage
As explained on p. 267 the index of female moth mortality is related
to the fraction of females which did not deposit their total quantity of
eggs due to pre-senile mortality or emigration. When the k-value of
this index (kJ is plotted over moth density, then the regression coefficient turns out to be 0.12, but it does not differ significantly from zero.
Therefore this factor cannot be considered as being density dependent.
Hence, if there is a night movement of females (cf. p. 267) then its
intensity is most likely not affected by density.
5. conclusion
Summarizing the results of this analysis we ca:n state that density
dependent mortality factors were found operating among advanced
larvae only. The regulating power of the density governed relationship
appeared to be insufficient, even in co-operation with the density induced variability of the fecundity, to account for the total density related action shown to be present. Therefore, it is most likely that in
293
density of the previous year (log Lt) results in a regression coeficient of
0.38 (Fig. 38-A). If the former is plotted over the product of the latter
and the fraction of advanced larvae surviving (log Lt . sPp5 = the logarithm of nymphal density), then the coefficient iricreases to 0.52 only
(Fig. 38-B). This suggests that a good deal of density governed reactiqn
must be present in other components, and the weak density induced,
variability of fecundity alone cannot account for this.
(c) Prepupal Mortality. If the k-values of prepupal mortality (k,) are
plotted over nymphal density there proves to be 110 relation.
3. Mortality in the Pupal Stage
The results of the regression analysis shown in Fi,z. 33 and Table XXV
suggest that pupal mortality includes a weak density related factor. In
principle this can be both delayed and direct density dependent, because the mortality is partly determined by parasites operating mostly
in the preceding summer, and partly by predators (and disease), which
are especially active in the period March to June. In this section the
possible occurrence of density dependent factors hits been studied only.
The parasites are considered in a later sub-chapter.
There proves to be no relation between total pupal mortality (k,-J
and pupal December density. Nor is there any relation between the
k-value of non-parasitic mortality and pupal density. From these
results it is concluded that there is no direct density dependent effect
included in this age-interval mortality.
4. H t a l i t y in the Moth Stage
As explained on p. 267 the index of female moth mortality is related
to the fraction of females which did not deposit their total quantity of
eggs due to pre-senile mortality or emigration. When the k-value of
this index (kJ is plotted over moth density, then the regression coefficient turns out to be 0.12, but it does not differ significantly from zero.
Therefore this factor cannot be considered as being density dependent.
Hence, if there is a night movement of females (cf. p. 267) then its
intensity is most likely not affected by density.
5. conclusion
Summarizing the results of this analysis we ca:n state that density
dependent mortality factors were found operating among advanced
larvae only. The regulating power of the density governed relationship
appeared to be insufficient, even in co-operation with the density induced variability of the fecundity, to account for the total density related action shown to be present. Therefore, it is most likely that in