ABSTRACT
This chapter discribes the factors controlling changes in insect abundance and distribution over time and space. The frequent appearance of insects en masse with no obvious explanation supported early perceptions of “spontaneous generation” and “acts of God”. Predicting the effects of global change has generated increased interest in insect population dynamics and future effects on human health and ecosystem services. A number of hypotheses have been proposed to explain cyclic population dynamics. Climatic cycles provide one explanation, but regular irruptions of larch bud moth have occurred for 1,200 years in the European Alps independently of warming and cooling trends. Insect populations are highly sensitive to changes in abiotic conditions, particularly temperature and water availability, which affect insect growth and survival. Competition for limited resources and mortality to predation and parasitism are the primary biotic factors limiting population growth. Regulation occurs when controlling factors function to maintain a relatively constant population size, typically around the carrying capacity of the environment.
