8 THE BRITISH HEMIPTERA. 



many are restricted to a single family (indeed we have 

 repeated instances of a section containing only a single 

 species. 



The 19 sections are distributed amongst three subdivisions 

 — the Geodromici (or terrestrial species), comprising 12 sec- 

 tions ; the Hydrodromici (or super-aquatic species),* com- 

 prising 2 sections ; and the Aquatilia (or sub-aquatic spe- 

 cies), 5 sections. 



The two first-named subdivisions form together the division 

 Gymnocerata (with exserted visible antennae), and the Aqua- 

 tilia, with another subdivision, Litoralia, not represented in 

 this country, (and which, indeed, consists of only a single 

 species, Pelogonus marginatiis, which occurs in the south of 

 France and in Spain,) form the division Cryptocerata, in 

 which the antennae are very short and concealed in cavities 

 beneath the eyes. 



These two divisions, Gymnocerata and Cryjytocerata, to- 

 gether form the sub-order Heteroptera, 



The Heteroptera, as the name implies, are most readily 

 distinguished from the Hoynoptera by the structure of the 

 wings— in the Homoptera "the wings are all membranous, 

 the anterior pair not overlapping each other ;" in the Hete- 

 roptera " the anterior pair posteriorly overlap each other, 

 the basal portion is coriaceous, the apical portion membra- 

 nous, the posterior wings are membranous." 



The Homoptera thus foim a very distinct group, and 

 in the fiist instance the authors of the volume before us, 

 have probably done well to confine their attention exclu- 

 sively to the Heteroptera, The preface informs us, that they 

 '' hope hereafter to produce a volume on the British Hemip- 



* Hebrns pusillus, which walks on Lemna and other aquatic plants, 

 placed by Fieber amongst the Hydrodromici, next to Limnohates stag' 

 norum, is here removed to near the centre of the Geodromici. 



