86 



It is evident, from a comparison of fossil insects with existing 

 species, that the temperature of Europe has undergone sensible 

 modifications ; and the distribution of genera, the size of the 

 specimens, as well as the numerical relations existing between 

 various groups, indicate the former existence of warmer climates 

 than those now prevailing in the same parts of Europe. 



Professor Heer has noticed that the development of insects 

 has been influenced by that of the Vegetable Kingdom, certain 

 species not having appeared prior to the period at which 

 dicotyledonous plants are supposed to have attained their liighest 

 state of development. 



It has been remarked by M. Oustalet that each formation, or 

 rather each deposit, on the Continent, in which fossil insects 

 have been detected, is characterised by the prevalence of 

 some particular family or order. Thus the genus Blatta is 

 especially well represented in the Lias of Aargua, the 

 Ehjnchophora in the Marls of Aix ; the Buprestidoe. in 

 the quarries of CEningen; the Ants in the sulphurous marls 

 of Kadoboj; the Termites in the Baltic Amber, &c. This 

 seems satisfactory evidence that each one of these groups found 

 in its locality, at the period of its existence, all the essential 

 requisites for its develojjment. 



I have a good deal to say on this subject, as well as on that 

 of the dates of apparition of the various orders of insects on the 

 Geological horizon. I shall, however, reserve my observations 

 until the end of the 3rd paper of the series, when having brought 

 under revieAv the various formations of the Recent, Tertiary* 

 Secondary, and Primary Periods, in which insect remains have 

 been discovered, I shall be better able to draw general conclusions 

 than I am in the introductory portion of the let paper. 



I will now proceed to notice the various formations in which 

 fossil insects have been detected, and the orders, families, and 

 species, to which such fossils have severally been referred. 



