360 On the Geographical Distribution of Insects. 



much more essential to know their geographical distribution 

 according to their functions, that is, according as they derive 

 their nourishment from vegetable or animal substances. Of 

 this the table enables us to form a pretty accurate calculation. 



The families essentially and solely creophagous are the 

 Carabidas and Hydrocanthares. Four others, the Brachely- 

 tres, Teredyles, Clavicornes, and Palpicornes contain a mix- 

 ture of carnivorous and phytophagous species, probably about 

 the one-half being of the former description, the other of the 

 latter. All the other families are phytophagous. 



Foimding our estimate on these considerations, we find that 

 of the 24,650 species mentioned in the preceding table, 4752 

 are creophagous, and 19,898 phytophagous, that is to say, the 

 first are to the second : : 1 : 3,97. 



A very different result will be obtained, if a similar calcula- 

 tion be made regarding the entire class of insects, for, accord- 

 ing to the above estimate, the carnivora would be to the phyto- 

 phaga about : : 4 : 9. Kirby and Spence making a similar inquiry 

 regarding 8000 English insects (including Arachnides), esti- 

 mate the proportion at nearly one- half. What renders the cal- 

 culation more complicated when extended to the entire class, is, 

 that a multitude of species are creophagous in their first con- 

 dition, and phytophagous in their last, while in the case of the 

 Colepotera the mode of nutrition is more uniform. 



A second consequence resulting from the table, one already 



alluded to, is, that the relative proportion of the creophagous 



( oleoptera diminishes rapidly as we approach the equator. 



I hey bear the following relation to the totality of the species 



ill the regions indicated : 



New Continent. 

 North America, . . . . : : 1 : 4,01 



South America, . . . . : : 1 : 9,59 



Old Continent. 



Siberia, : : 1 : 2,90 



Europe, :: 1:3,87 



Africa, : : 1 : 5,59 



Oceanea, : : 1 : 8,59 



But the creophagous species do not always take their food 

 in the same state any more than the phytophagous. Some 



