Overall rainfall is plentiful throughout the country, but most areas receive it seasonally.
Seasonally, the largest average clutches are produced in the middle of the breeding season, that is, in June.
Zapus princeps is locally abundant, but its numbers seem to vary considerably from year to year as well as seasonally.
The population of Z. hudsonius may vary considerably from year to year as well as seasonally.
Similar results have been obtained with the seasonally dimorphic Pieris napi.
The summer generations of seasonally dimorphic butterflies the more variable, 42.
Caterpillars, pup and eggs of summer and winter generations of seasonally dimorphic butterflies alike, 64.
Here again the case is quite similar to that of seasonally dimorphic butterflies.
A slightly more refined way of comparing the frequency distributions is to relate them to other, seasonally variable phenomena.
No correlation between any seasonally variable factor and the number of captures per individual was apparent.