More than 30 fossil coleopteran (beetle) assemblages have been recorded from oxygen isotope stage 3 in northern Europe, comprising several hundred identified species. Using the mutual climatic range method for quantifying palaeotemperatures, these assemblages show that the climates of the times can be divided into two distinct interstadial types. One, a short phase of temperate/oceanic climate occurred between 43,000 and 42,000 14C yr B.P. when conditions were not much different from those of the present day. In spite of the temperate climate, trees did not colonize northwestern Europe at this time. Two, both before and after this temperate interlude there were phases of cold/continental climate during which summers were too cold for trees to grow and winters were of Siberian intensity. It is possible that periods of even colder conditions intervened from time to time between the interstadial but, because of the intensity of the cold, biological systems were so inhibited that no fossil evidence for them can be found in northern Europe. Evidence for them must be sought in the fossil records from the warmer parts of southern Europe or in the physical evidence in the Greenland ice cores.

Assemblages of fossil coleoptera (beetles) have been obtained from eight sites in southern England that date from the early phase (Pinus — Quercetum mixtum — Corylus pollen assemblage zone) of the Eemian (Ipswichian) interglacial Stage. Altogether 294 different species have been identified from these sites. They represent a wide spectrum of habitat requirements; terrestrial, aquatic, carnivorous and phytophagous species and many more with subtle dependences of specialist biotopes. Almost all of them live today in central and southern Europe and some are restricted to regions well south of the British Isles.

By using mutual climatic range methods, the thermal climate of the early phase of the Eemian Interglacial has been estimated quantitatively, showing that mean July temperatures were about 4°C above those of southern England today. Mean winter temperatures were not much different from those nowadays. This phase was probably the thermal maximum of the Eemian Interglacial. Precipitation levels are difficult to quantify but were adequate to maintain flowing rivers in England throughout the year. These results are in agreement with the presence of other fossils, both plants and animals, in the same deposits.