612 



TAXONOMY. 



* Mandilmlate mouth. 



Cases homy. Perfect meta- 4. Order. Coleoptera. 



morphosis. 

 Cases horny. Imperfect me- 5. - 



tamorphosis. 

 Cases coriaceous. Imperfect 6. - 



metamorphosis. 



** Suctorial mouth. 7- Hemiptera. 



b. Gymnoptcra. Wings alike. 



* Four wings. 



t Mandibulate oral organs, at 

 least distinct mandibles. 



Dermaptera, the 

 genus Forficula. 

 Orthoptera. 



Wings with reticulated ner- 8. 



Neuroptera. 

 Hymenoptera. 



vures. 

 Wings with ramose ner- 9. 



vures. 

 tt Suctorial mouth, mandibles 10. Lepidoptera, 



abortive. 

 ** Two wings. 



t Two distorted moveable pro- 11. Strepsiptera. 



cesses on the prothorax. 



tt Poisers behind the wings. 12. Diptera. 

 We have not space here to enter into the merits of this system, and 

 we can only remark that the author has made divisions upon mere 

 external characters, and that, therefore, the naturalness of his grouping, 

 which he chiefly aimed at, was necessarily lost. This may be asserted 

 also of the families within the orders; they are also frequently deficient 

 in a natural connexion and a natural arrangement. 



346. 



Whilst Latreille was elaborating the natural system during a space 

 of thirty-six years, other countrymen of his were busied with the same 

 subject. Lamarck is the first among these. He first proposed the 

 separation of the Arachnides as a class, and he separated the Insecta 

 of Linnaeus into the three equivalent groups, Crustacea, Arachnides, 

 Insecta. The Insecta he subdivided into eight orders, as follows : 



