444 SYSTEMATIC ARRANGEMENTS OF INSECTS. 



companion to Humboldt's famous Geography of Plants. 

 He divides the globe into twelve insect zones or climates, 

 thus :— 



I. Arctic, aU North of the Equator. 



1. Polar. 5. Supra-tropical. 



2. Sub-Polar. 6. Tropical. 



3. Superior. 7. Equatorial. 



4. Intermediate. 



II. Antarctic, all South of the Equator. 



1. Equatorial. 



2. Tropical. 



3. Supra-tropical. 



4. Intermediate. 



5. Superior. 



Connected with this subject is the doctrine of Representa- 

 tion and Replacement, by which it is maintained, that when 

 a particular species of insect, or rather animal, is not 

 found in two several countries or districts, such as Britain 

 and New England, it is represented or replaced by some 

 species resembling it in form and in function. Taking a 

 more popular example than insects furnish, it is held, ac- 

 cording to this system, that the puma of America replaces 

 the lion of Africa, or that the pecari represents in Mexico 

 the hog of Europe. 



The Transformation System. 



There are considerable differences in transformations 

 among various species. These, the illustrious Swammer- 

 dam, whose accurate observations are now as valuable as 

 when they were made nearly two centuries ago, has made 

 the basis of his system. 



Swammerdam' s Classification. 



I. Transformations immediate, the insects being hatched perfectly 

 formed— fleas, spiders, &c. 

 II. Transformations taking place under a covering*— locusts, crickets, 



bugs, di'agon-flies, May-fl.ies, &c. 

 III. Transformations with a pupa-case intermediate* — beetles, bees, 

 wasps, saw-flies, gnats, &c. 



* In explaining Swammerdam's system, Kirby and Spence use tlie 

 terms of " complete " and " incomplete," which are not in the original. 



