602 TAXONOMY. 



therefore, very constant groups, were formed, but, s often the case, 

 when, in the arrangement of natural bodies, only due principle of 

 division is adopted, others comprise, in every instance, very different 

 animals. This deficiency must necessarily be recognised upon con- 

 tinued inspection, and, therefore, an anxiety must exist to remove 

 it as much as possible. Above all, the order of the Hemiptera is 

 subject to many objections, for, in the first place, the character 

 attributed to it is not found in many of its members., for instance, 

 in many Cicada, the Aphides, the genus Chermes, &c., as they pos- 

 sess four perfectly membranous wings, and., secondly, there are 

 insects united in it, which exhibit the greatest differences in their oral 

 organs. 



These circumstances caused the next systematist after Linnaeus, 

 who was also a Swede, namely, De Geer, to separate the Linnaean 

 Hemiptera into several equivalent groups, as well as to the adoption of 

 a new system, which is the following : 



I. Insects with wings. Alata. 

 A. Gymnoptera. 



1. Lepidoptera. 



2. Elingula (Ephemera, 8tc.). 



3. Neiiroptera (Libellulce and other Linnaean Neuropiera). 



4. Hymenoptera. 



5. Siphonala (Aphides and Cicada). 



B. Vaginata. 



(). Dermaptera ( bugs and water-bugs). 



7- Hemiptera (cockroaches and grasshoppers). 



8. Coleoptera (beetles). 



C. Diptera. 



r 



9. Halter ata (Linn&us, Diptera). 



10. Proboscidea (the genus Coccus). 



II. Insects without wings. Aptera. 



D. Saltatoria. 



11. Suctoria (the genus Culex). 



E. Gressoria. 



12. Aucenaia (the genera Lepisma, Podnra, Termes, Pedi- 



culus, and Ricinus). 



13. Atrachelia (the spiders and crabs). 



14. Crustacea (the Isopoda, Ampiphoda, and Myriupoda of 



Latreille. See below). 



