Effect of Rainfall-Evaporation Ratio on Insects Inhabiting the Soil Surface

Abstract

CERTAIN insects inhabiting the soil surface are markedly affected by soil moisture, largely owing to its influence on the humidity of their surroundings. Soil moisture is primarily dependent on the ratio of rainfall to evaporation (R/E); important secondary factors being soil type and its vegetative covering. If values for the R/E ratio in an area are known, a useful index to the conditions in the micro-environment at the soil surface is available for ecological studies¹. Evaporation from a free water surface is nearly proportional to the saturation deficit of the air, other variables being constant. Saturation deficit is available for stations where temperature and relative humidity are recorded, and evaporation values can be determined approximately by reference to evaporation records for comparable stations. Owing to the variables involved, particularly wind and the character of the soil surface, the computed values can be only roughly approximate.