Test baiting has shown that rats underground are distributed in a series of discrete colonies, each one in close association with a group of men. Interplay between colonies is rare in large mines although evident in small ones. In the absence of stables the rats must depend almost entirely on miners’ food scraps.

These observations were made during work carried out under a research grant from Safety in Mines Research Establishment, Ministry of Power, and I am indebted to the Ministry for permission to publish the results. I should like also to express my gratitude to Dr E. T. B. Francis who supervised the work, Mr. C. S. W. Grice of the Ministry of Power and Miss B. B. Jones of the Ministry of Agriculture, Fisheries and Food for their help in various aspects of the work.