The Corixidæ of the Faeroe Islands, with Observations on the Geo‐graphical Distribution of Corixidæ in Neighbouring parts of the World

Summary.1 Extensive collections of Corixidæ from the Faeroes have produced only Corixa carinata and C. wollastoni ; it is suggested for various reasons that these are the only species which exist there. The collections have been analysed in order to investigate ecological factors which affect the fauna. 2 The specimens differ from British specimens of the same species in being considerably smaller, but in little else. 3 The sex‐ratio in the collections is surprisingly low. The adult‐nymph ratios indicate that the majority of nymphs become adult by the second half of October. 4 Stagnant pools produce far more Corixidæ than other types of water‐body; the composition of the Corixid fauna in these pools is dependent upon the amount of vegetation, and to a less extent upon altitude; hydrogen‐ion concentration in the islands does not vary within wide limits, and has little or no effect. 5 The origin of the Corixid fauna is discussed and the conclusion is reached that the two species are a relict fauna which survived the Glacial era in the islands and that they did not subsequently reach the islands by immigration. 6 The Corixid fauna is very limited; the paucity of species is due not to adverse climatic or other conditions existing in the islands at the present day, but to extermination during the Glacial era of any other species which may have existed before it, and their inability to re‐colonize it since by migration; this opinion is borne out by comparison with the Corixid fauna of other islands and countries.