46 REMARKS ON THE GEOGRAPHICAL 



stance in the geography of insects; namely, that their tro- 

 pical structure extends much farther north in America 

 than in Europe ; that is, in a manner directly the reverse 

 of that which we have seen to be followed by plants. Ex- 

 amine Copris carnifex, F., Cetonia nitida, F., Rutela 6- 

 punctata, Lat., and other New York insects, and compare 

 them with insects of the same families from Brazil. The 

 difference between the general structure of these will be 

 found infinitely less than that which would result from a 

 comparison of the entomological productions of the neigh- 

 bourhood of Madrid with those of the banks of the Congo. 

 Nevertheless, though I contend that the insect tribes 

 suffer less in cold climates than plants, and hope to have 

 proved it to be the case, it does not therefore follow that 

 the prevalence of cold has no effect towards the destruction 

 of insect life. We know the very reverse of this to be the 

 truth, and that the diminution of the number of species 

 becomes very conspicuous as we advance towards the 

 poles. But this I imagine is owing to the short continu- 

 ance of warmth rather than to the low deo-ree of it while 

 it exists ^. And accordingly we find that insects, such as 

 gnats, musquitoes, &c., which pass their larva state in 

 water, thus avoiding extreme cold, and whose existence 

 in their perfect state being naturally ephemeral, must 

 therefore suffer little from the shortness of the summer, — 

 are no -where more troublesome than in the very coldest 

 climates. Whereas the number of coleopterous insects, 

 which, being naturally longer lived, require a longer conti- 

 nuance of warmth, is sensibly diminished' in these dreary 

 countries. 



* Heat, properly speaking, never absolutely ceases to exist; but it is 

 here for coiiveiiienqe understood as commencing at 32° of Fahrenheit. 



