26 THE ENTOMOLOGIST. 



of this epoch the arctic climate receded towards the poles, 

 and was followed by vegetation and by the insect race in 

 successively smaller or less varied zones. By this means 

 the vast variety in the range of insect-life has been effected, 

 and the time here mentioned was preparatory to the present 

 aspects of nature, just as winter is succeeded by the scenery 

 of summer. A large part of the insect species still continue 

 in their former habitation ; another large part have wholly 

 departed from the tropical regions, and have settled in 

 temperate countries, while a few are cosmopolitan or 

 universal, and bind, as it were, the whole Fauna together. 

 Some kinds pass occasionally from one district to another, 

 and thus, like the annual migration of others, indicate 

 slightly the great change that formerly occurred. As the 

 cold climate diminished, the arctic and alpine species 

 removed to higher levels or to higher latitudes, and ceased to 

 exist in the intervening temperate regions, just as many of 

 the present inhabitants of the latter have wholly left the 

 warm lands which are now unsuited to them, and to the 

 vegetation with which they are associated. A notice of the 

 settlements and range of an insect family may begin with the 

 low latitudes, its earlier dwelling-place ; and it may be traced 

 thence in its lines of convergence to the high latitudes, these 

 lines being occasionally shortened or turned aside by inter- 

 vening seas, or mountains, or deserts. The Aphis family is, 

 as yet, very little known in low latitudes, and there are only- 

 two instances of its occurrence to the south of the equator. 

 The first is a Madagascar genus, published by Coquerel : 

 this genus has the fore wings more highly organized than 

 those of any other known form of the tribe. The second 

 dwells near New Caledonia, and is described by Montrouzier, 

 and has much resemblance to some of the European Aphides. 

 In Dr. Leith's collection of Bombay insects, I have observed 

 an Aphis which, if its specific characters are not obliterated 

 by its shrivelled condition, is identical with a common 

 English species. The next record of the family is in North 

 Italy, where Passerini has published a monograph of the 

 species therein. Africa, Asia and Australia are thus almost 

 undiscovered countries as regards Aphides, and afford a 

 large space and require much time for research. The 

 Aphides of America are unknown from the Southern end to 



