The relation between migration‐rate and type of habitat in aquatic inseets, with special reference to certain species of Corixidae.

SUMMARY.1 In a newly filled pond at Haileybury and Imperial Service College, Hertfordshire, the progress of colonization by Corixidae was studied in the spring and early summer of 1949, and again in 1950. The different species appearing were recorded, and compared numerically from sample collections. 2 The ratio of the numbers migrating into the pond to the numerical abundance of the same species in the surrounding district gave a rough comparison of their migration‐rates, which agreed closely with results obtained by other methods. 3 Migration‐rates of different species were found to be correlated with the types of habitat which they normally frequent; those normally found in temporary habitats migrate much, while those found in permanent habitats migrate relatively little. Those species of Corixidae whose migration‐rate is restricted by brachypterism are also confined to permanent habitats. 4 The significance of this correlation between habitat‐type and migration rate is discussed. A high rate of migration is advantageous to species frequenting temporary bodies of water, and a low one to those frequenting permanent habitats. Such a correlation may be more widespread, not only in Corixidae but in other aquatic insects such as beetles. 5 The factors controlling migration‐rate are ( a ) anatomical , involving reduction of wings (brachypterism) or of wing muscles (as in the beetle Noterus and the Hemiptera Nepa, Ranatra, Hyocoris ), or both; and ( b ) of some other nature, probably physiological , which affect migratory tendency and behaviour ( e. g. Corixidae).