Ecological Studies of the Commoner Species of British Corixidae

Abstract

Although the Corixidae (Hemiptera, Heteroptera) are to be found in almost any pond and pool throughout the country, yet very little has been written about the factors responsible for the distribution of the various species. By far the most important paper is that of Macan (1938) who has made a detailed analysis of a large number of habitats in the Lake District, and shown that there is a close relationship between the percentage of organic matter in the soil (% o.m.s.) and the species of Corixids living there. On a previous occasion the writer (Popham, 1941) has shown that certain species of Corixidae not only vary in colour, but that they tend to agree with that of the pond in which they occur. This agreement was thought to be due to the following factors: (I) the action of predators in destroying those insectF not adapted to the background; (2) the action of the background in controlling the intensity of pigmentation of nymphs and young adults, and (3) choice by the adults of a background with which they harmonize. Studies on the last two are recorded in the present paper. At the time of writing (I942), the classification of the Corixidae is in a state of flux. Mr China of the British Museum has drawn my attention to a classification by Walton (in Hutchinson, 1940) who has divided the genus 'Corixa' into some nine subgenera; but until this system has been confirmed by other authorities, it has been decided to follow the nomenclature of Macan (1939). The generic name 'Arctocorisa' is therefore used for 'Sigara'. The Ostwald Colour Chart has again been used as a standard and the percentages of white in the various standards are: