90 THE WORLD OF LIFE 



and here we find the total number of the Lepidoptera in 

 Essex, which is not far from an average county, very nearly 

 the same as its area. The number of species of these insects 

 is also suggestive, in being about one-half greater than the 

 number of flowering plants (1010) on which they almost all 

 feed in their larval state. We know that many different 

 species feed on some of our commonest plants — as the oak, 

 poplar, elm, nettle, etc. — while some larv^^e feed on several 

 distinct plants indiscr,iminately. But probably the larger 

 number feed on one species of plant only, and thus almost all 

 our plants, except the very rarest, afford food for at lea^t one 

 lepidopterous larva. 



Again, just as we found that a selected area of 10 square 

 miles in Surrey had nearly two-thirds of the plants in the 

 whole county, so here we find that a selected area of 10 square 

 miles in Essex has nearly two-thirds of the Macrolepidoptera 

 found in the county. Here, too, we see the result of the de- 

 pendence of the insects on the plants, the great variety of 

 the latter in Epping Forest (150 species) rendering possible 

 a corresponding variety of the former. 



Coleoptera (Beetles) 



The enormous order of the beetles (Coleoptera) not being 

 exclusively feeders on living plants, but both in their larval 

 and perfect state often feeding on animal food or on vege- 

 table debris, are probably more uniform in their numbers in 

 different areas if not absolutely barren or very highly culti- 

 vated. 



Area. Species. 



Great Britain 87,500 3260 



Essex 1,530 1655 



As it requires perseverance in collecting for many years 

 in order to obtain all the beetles in even a very limited 

 district, I think it probable that the above figures do not so 

 closely represent the actual number of species inhabiting the 

 county as in those given for the plants, or even the moths. 



