INSECTA. 
342 
the three finer seasons of the year produces species peculiar to it. The 
females and males of those which live in societies, however, enjoy a 
longer term of life. Individuals hatched in autumn shelter them- 
selves from the rigours of winter, and reappear in spring. 
The species, like those of plants, are circumscribed within geogra- 
phical limits. Those of the western continent for instance, a very 
few, and all from the north, excejjted, are strictly peculiar to it; such 
also is the case with several genera. The eastern continent, in turn, 
possesses others which are unknown in the western. The Insects of 
the south of Europe and north of Africa, and of the western and 
southern countries of Asia, have a strong mutual resemblance. The 
same may be said of those which inhabit the Moluccas, and more 
eastern islands, those of the Southern Ocean included. SeA^eral 
northern species are found in the mountains of southern countries. 
Those of Africa differ greatly from the opposite portions of America. 
The Insects of Soirthern Asia, from the Indies on the Sind eastward, 
to the confines of China, are very much alike. The intertropical 
regions, covered rvith immense and well-watered forests, are- the 
richest in Insects of any on the globe ; Brazil and Guiana are 
particularly so. 
All general systems or methods relative to Insects are reduced 
essentially to three. Swammerdam based his on their metamor- 
phoses ; that of Linnaeus Avas founded on the presence or absence of 
wings, their number, consistence, superposition, the nature of their 
surface, and on the deficiency or presence of a sting. Fabricius had 
recourse to the parts of the mouth alone. In all these arrangements 
the Crustacea and Arachnides are placed among the Insects, and in 
that of Linnaeus, the one generally adopted, they are even the last. 
Brisson, however, had separated them, and his class of the Crustacea, 
which he places before that of Insects, comprises all of those animals 
which have more than six feet, or the Insectes Apiropodes of M. 
Savigny. Although this order is more natural than that of Linnaeus, 
it was not followed ; and it is only in modern times, that anatomical 
observations and their rigorously exact application have brought us 
to the natural method *. 
I divide this class into twelve orders : the three first of which, 
composed of apterous Insects, undergoing no essential change of 
form or habits, merely subject to simple changes of tegument, or to a 
* Cuv., Tabl. El^m. de I’Hist. Nat. des Anim., and Lemons d’Anat. Compar. ; 
Lamarck, Syst. des Anim. sans Vert^b. ; Latr., Precis des Caract. Gendr. des Insect., 
and Gen. Crust, et Insect. For more minute details, see also the excellent elemen- 
tary work of Kirby and Spence. 
