264< NATURAL ARRANGEMENT OF INSECTS. 



ceding sub-family were the giants of the Carahidop, so 

 are these the dwarfs, for amongst them we have some 

 of the smallest Carabideous insects. They all frequent 

 humid situations ; and many, when captured, exhale 

 offensive odours : they are exceedingly active, as their 

 names frequently indicate, — for instance, Tachys, Ocys, 

 Tachypus, which have all reference to this peculiarity ; 

 and from this, in combination with their habitat, 

 they might not inaptly be styled coleopterous 'Wills o'the 

 wisp. By means of the little gibbous genus Onwphron, 

 the present family merges into the next, for it has a 

 most remarkable resemblance to Haliplus and Cne- 

 midotus. 



(234.) The Hydrodephaga, or Dytkcidcp, constitute 

 our third family. This group, compared with the 

 former, is of very small extent. They retain all the 

 prominent characters of the preceding family ; for, being 

 aquatic Cai-abidrp, their structure is only so far modified 

 as to suit the different element they are intended to in- 

 habit ; and the reason of the smaller diversity of form 

 observable in them throughout all latitudes, is the limit- 

 ation and uniformity of the functions they have to 

 execute. The only peculiarity we remark in their dis- 

 tribution is, that Cybister is evidently tropical, for of 

 it we have but one representative in this country, and 

 only three species occur to the north of 35° of northern 

 latitude; whereas Dytiscus, which here takes its place, 

 does not occur to the south of the Tropic of Cancer. 

 The males of all the larger genera of these insects are 

 remarkable for the scutellated enlargement of their an- 

 terior tarsi, which form frequently a circular disk sup- 

 plied beneath with a cluster of small sucking cups for 

 the purposes of sexual adhesion ; and a peculiarity in the 

 majority of the females of males so furnished, is to have 

 their elytra deeply furrowed longitudinally. They are 

 exceedingly voracious insects in all their stages, but es- 

 pecially in the larva state; for all that their strength or 

 dexterity can overcome do they prey upon, and small 

 fish and the fry of larger ones are not free from their 



