INVERTEBRATE ANIMALS. 87 



by J. 0. Westwood, F.L.S., 2 vols. 8vo., 1839. The 

 classifications adopted by Haeckel, Huxley, Ray Lan- 

 kester, Macalister, Nicholson, Packard, and Wyville 

 Thomson, all differ in important particulars ; and are 

 too concise to admit of being used as text-books for the 

 sub-divisions of the Class, the true genetic order of 

 which is manifestly yet a desideratum. As a guide to 

 the morphology and habits of the Hexapoda, Professor 

 Westwood's work can hardly be surpassed. 



Order HETEROPTEEA. hspog, different ; Trnpov, 

 a wing. Insects having their fore- wings chitinous or 

 leathery towards the base, and membranous towards 

 the apex. Estimated number of species : total, 1,350 

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



Group 197.-HETEROPTERA-HYDROCORISA. vdojp, water; 

 xo'pij, a bug. 



This portion of the Heteroptera is made up of 

 aquatic insects, of which the species are not numerous. 

 ^ Examples of Water-scorpions, Nepa ; Boat-flies, 

 Notonecta ; and of the only truly oceanic genus 

 of insects, Halohates ; specimens presented by 

 Capt. Mortimer. Observe the arrangement of 

 the eggs on the back of Zaitha ; how were they 

 placed there ? 

 Small series of British species collected and pre- 

 sented by H. H. H. 

 The division Ametabola here introduced, consisting 

 of insects which undergo no transformations, includes 

 three orders of which the species are all of small size : 



I. Order Akoplura. Lice, with sucking mouths. 

 Pedicididce. 



