Although almost as exclusively insectivorous as bats, moles and shrews do not, so far as is known, hibernate. This distinction between two groups so nearly alike in diet, no doubt depends upon the difference in their habitats and in those of the creatures they live upon. By tunnelling deeper in winter than in summer, moles are still able to find worms and various insects buried in the earth beyond the reach of frost; and shrews hunt out spiders, centipedes and insects which in their larval, pupal or sexual stages have taken shelter and lie dormant in holes and crannies of the soil, beneath the leaves of ground plants or under stones and logs of wood. In view of the perennially active life of the two insectivora just mentioned, it is a singular fact that the common hedgehog (_Erinaceus europaeus_)--the only member of this order besides genera referable to the moles (_Talpidae_) and shrews (_Soricidae_) that inhabits temperate and north-temperate latitudes in Europe and Asia--passes the winter in a state of torpor unsurpassed in profundity by that of any species of mammal so far as is known. Possibly the explanation of this seeming anomaly may be found in the bionomial differences between the three animals. The subterranean feeding habits of the mole render hibernation unnecessary on his part. Therefore the shrew and the hedgehog, both surface feeders for the most part, need only be considered in this connexion. As compared with shrews, amongst the smallest of palaearctic mammals, the hedgehog is of considerable size. Moreover, in point of vivacious energy it would be difficult to find two mammals of the same order more utterly unlike. Hence in winter when insects are scarce and demand active and diligent search, it is quite intelligible that the shrews, in virtue of their smallness and rapidity of movement, are able to procure sufficient food for their needs; whereas the hedgehogs, requiring a far larger quantity and handicapped by lack of activity, would probably starve under the same conditions. Like the common hedgehog of Europe, the long-eared hedgehog (_Erinaceus megalotis_) hibernates in Afghanistan from November till February. The tenrec (_Centetes ecaudatus_), a large insectivore from Madagascar, aestivates during the hottest weeks of the year; and specimens exhibited in the Zoological Gardens in London preserved the habit although kept at a uniform temperature and regularly supplied with food.