On Aquatic Carnivorous Coleoptera 07- Dyf.iscida>. 931 



tropical South America, tlie Pacific Islands (including New Caledonia) or the 

 Malayan and tropical Asiatic regions. The one or two species found in New Zea- 

 land are very closely allied to Australian species. Australia (with Tasmania) 

 possesses five genera (containing about thirty species) peculiar to itself, but the 

 great majority of the species are found in the North American and European regions, 

 where the three genera Ccelambus, Deronectes, and Hydroporus are represented 

 by about 260 species. No member of the group has yet been found in Japan, 

 so that in this respect Japan and tropical Asia agree, and are very different from 

 Europe. 



II. 10. — Group Agabini. {Vide p. 491.) 



This aggregate of the second degree is formed by ten primary aggregates which 

 include one hundred and forty-four species. The size of the individuals varies from 

 6 m.m. to 14 m.m. of length, so that in the stature of the individuals the group 

 stands at about the central point of the Dytiscidae. 



The upper surface is very rarely indeed possessed of a true punctuation, its place 

 being taken by a reticulation of fine scratches, forming meshes of various shapes 

 and magnitudes, according to the species ; sometimes this sculpture becomes exces- 

 sively fine, and occasionally the surface is smooth and polished. The colour is 

 usually obscure, or dark with a brassy tint ; few species are variegate. 



The characters of the group are that the semimembranous piece bordering the 

 inner edge of the first ventral segment is smooth, and not thrown into transverse 

 folds as it is in the Colymbetini ; the apex of the wing of the metasternum reaches, 

 when the wing-cases are closed, to the edge of the epipleura ; the hind femur bears 

 on its undersurface, at the extremity and quite close to the hind margin, a more or 

 less developed group of ciHte ; and the side piece of the fourth and of the follomng 

 ventral segments is comparatively broad. 



The first of these characters is merely a negative one, and by it -the Agabini 

 depart from the Colymbetini to agree with the vast majority of the Dytiscidae. 



The character drawn from the relation of the points of the metasternal wings to 

 the epipleurae is of little consequence, and moreover is not absolute but is rather 

 one of degree : it depends on the fact that the metathoracic episternum (placed at 

 the antero-external portion of the metasternum) proceeds backwards between the 

 edare of the winsr-case and the wincj of the metasternum till it terminates as a sharp 

 point, contiguous with the point of the metasternal wing ; this character however 

 is not absolute, for in Dytiscus ater (No. 781) the exposed terminal portion of the 

 episternum is not a sharp point, but is truncate ; the point of the metasternal 

 wing in that species does not therefore reach absolutely so far as the epipleura, 

 although it approaches very near indeed thereto. 



In those species of the aggregate that have the swimming legs but little developed, 

 the femoral cilise are, Hke the legs themselves, less highly developed and perfect : 



TIIANS. BOY. DUB. SOC, N.S., VOL. U. " ^ 



