Mortality Rates of the Mobile and Immobile Stages in the Life-Cycle of Carabids

Abstract

The aim of this report is to outline possible influences of population density and individual mobility on mortality rate of carabids. According to my previously published results (Grum, 1975a) the instantaneous mortality rate changes greatly from one stage in the life-cycle of carabid species to another. Namely, the mortality rates calculated for larvae and breeding beetles are much higher than those calculated for incubating eggs, pupae, and hibernating beetles of the same generation. Thus there is no simple relation between the initial population density of a stage and its instantaneous mortality rate or, in other words, density-dependent mortality does not seem to operate. Contrary to that, direct influence of individual mobility seems to be responsible for changing mortality rates:the rates estimated for the immobile stage in the life-cycle (e.g., eggs, pupae, and hibernating beetles) are much lower than those estimated for the mobile ones (e.g., larvae and breeding beetles). In addition, all the mobile stages produce biomass (body weight increase and/or egg or sperm production), and the non-productive stages are immobile.