A population model for two species of Tipula (Diptera, Nematocera) derived from data on their physiological relations with their environment.

Published results show that variations in mortality due to factors such as predation, parasitism and disease are overshadowed by variations due to effects of physical factors. Soil temperature and the tension of the soil moisture have a profound effect not only on the survival but also on the growth rate and fertility of the two species considered here. The model is based largely upon known and experimentally quantified relationships of causes and effects and is therefore a practical model which integrates our knowledge so that we can compare its results with reality to see if or where our knowledge is lacking.