84 INVERTEBRATE ANIMALS. 



three sub-classes. I. Ametabola ; Transformations 

 absent. II. Hemimetabola ; Transformations incom- 

 plete. III. Metabola ; Transformations complete. But 

 the advantage of this classification has in the present 

 instance been relinquished as incompatible with the 

 integrity of the Orders. Objectionable on the same 

 ground are the older divisions : I. Haustellata; Insects 

 with sucking mouths. II. Mandibulata ; Insects with 

 biting jaws. Groups 197-222 chiefly illustrate the 

 former, groups 223-2-40 the latter of these divisions. 



The order of the groups corresponds nearly with 

 the arrangement adopted in the " Introduction to the 

 Modern Classification of Insects," by J. 0. Westwood, 

 F. L. S., 2 vols. 8vo., 1839 ; one of the best books on a 

 subject of natural history that has ever appeared in the 

 English or in any other language. 



After some labour and much thought, the writer can 

 only come to the conclusion that the disadvantages of a 

 linear arrangement are nowhere more troublesome than 

 amongst the manifold affinities in this most instructive 

 class, Insecta. 



Order HETEROPTERA. eVepoc. different ; ^rrepov, 

 a wing. Insects having their fore-wings chitinous or 

 leathery towards the base, and membranous towards 

 the apex. Estimated number of species : total, 1350 

 (F. Walker, 1873) ; British, 354 (J. W. Douglas). 



Group 197.— HETEROPTERA -Hydrocorisa. u^cop, water; 

 Hopts, a bug. 



This portion of the Heteroptera is made up of 

 aquatic insects of which the species are not numerous. 



