Observations on the biology and physiology of wireworms of the genus Agriotes Esch

Abstract

Detailed studies of the growth of wireworms kept at a constant temperature of 15d̀ C. for 3 years and at natural soil temperatures for 2 years are presented. It is shown that small wireworms grow rapidly and moult frequently, but large wireworms grow slowly or remain constant in weight and moult infrequently. A basic pattern to account for the decreasing frequency of moulting during the life cycle is presented.The feeding activity and moulting frequency of a population of wireworms has been studied in detail throughout the season. Definite peaks in feeding activity and moulting frequency occur during the season. A suitable method for the analysis of such activity in a population has been found by dividing the population into groups on a basis of the number of annual moults.It is shown that increase in dry weight is a more valid estimate of growth than increase in fresh weight. The rate of growth of wireworms is strongly influenced by the food on which they feed: some plants (wheat and carrots) permit rapid growth; other plants (grass and clover) permit slower growth; while certain other plants (mustard and potatoes) allow the wireworm to maintain its weight. Wireworms reared on flax actually decrease in dry weight.In a field experiment it was found that the type of crop grown after breaking up old pasture had a distinct effect on the wireworm damage done to the following cereal crop. Beans had the effect of reducing the population to a level at which a very successful crop was grown. Better yields were obtained after wheat and grass than after the other crops, excepting beans, at similar levels of population.The cuticle of wireworms is permeable to water, and it is shown that in its relations to soil moisture the wireworm may be regarded as an osmotic system. The pF scale of soil moisture is shown to be of value in expressing the soil‐moisture relations of wireworms. Wireworms feed more actively in moist soil than in dry or wet soil.