An insect fauna of 172 taxa, chiefly of coleoptera, is described from Mid-Weichselian deposits at Brandon, Warwickshire. This fauna includes two species that are now believed to be extinct and thirty-three that are no longer found living in Britain. All but one of these species live today in Arctic or sub-Arctic regions of north-east Europe and northern Sibera-the single exception being an insect of decidedly steppe environments. The fauna as a whole indicates an open treeless habitat closely analogous to the northern tundras of the present day to which several of the recorded species are exclusively confined. Details of the local environment of the times are inferred from the fossil insect fauna. An interpretation of the climatic regime based on the northern requirements of the species in this fauna, suggests that conditions were more severe than for any other entomologically investigated site. A moderate degree of continentality is inferred and an attempt is made to give a range of average monthly temperatures through the year. A comparison of this fauna with other known fossil insect assemblages suggests that these may be of value in correlation of Quaternary deposits.