162 ADEPHAGA. [Laccoph Hus. 



Ponds, &c. ; widely distributed ; in the London district commoner than the pre- 

 ceding. Scotland, local. Lowlands, Tweed, Forth, Tay, Sohvay, Clyde. 



There is such confusion with regard to the synonomy of the tAvo last 

 species that without examining the specimens from each district it is 

 impossible to be certain of their distribution : one species only is 

 recorded from the ]S^orthumberland district, and one from Ireland, but I 

 cannot say which in either case, as the names minutus and liyalinus 

 have been applied to both species by different authors. Both species 

 •extend as far north as Lapland. 



Zi. varieg'atus, Germ. Smaller and narrower than the preceding ; 

 head testaceous ; thorax testaceous with anterior and posterior margins 

 dark ; elytra pitch-brown, almost black, with margins and a waved fascia 

 at base and another behind middle, interrupted at suture, testaceous ; 

 these are rather variable, and in some cases are hardly perceptible ; in 

 the male the anterior and middle tarsi are considerably incrassate, and 

 the last ventral segment is much produced in the middle ; in this latter 

 point, however, there is not much difference in this species between the 

 male and female ; the prosternal process is long and reaches beyond the 

 intermediate coxte ; in neither sex is there a coxal file. Long. 4, 

 lat. 2\ mm. 



Local ; apparently confined to the south-eastern parts of England ; Dover, Pe- 

 vensey, Deal, Pegwell Bay, Arundel, &c. ; it is a rare species on the Continent, and 

 does not extend further north than the south of England. 



DYTISCI COMPLICATI. 



The great bulk of tlie species of the family belong to this series : they 

 are distinguished by the fact that the middle coxal cavity, as explained 

 above, is enclosed by four distinct pieces, as the epistema of the meta- 

 thorax take part in the articulation. As Dr. Horn remarks (Classif. 

 Col. ISTorth America, p. 64), "they are to be regarded as the highest 

 Dytiscid type, in which not only the maximum size and force is 

 exhibited, but also the most perfect development of the oar-like legs." 



The series may be divided into the following tribes, to which, however. 

 Dr. Sharp, whose arrangement is followed, assigns very varying values. 



I. Prosternum deflected between the anterior coxae so that the 

 prosternal process is placed on quite a difl'erent plane from 

 that of the prosternum ; front tarsi usually four-jointed (in 



all our species this is the case) Htdeopoeina. 



IL Prosternum not deflected between the anterior cox£e; 

 front tarsi distinctly five-jointed. 

 i. Hind margins of joints of posterior tarsi not set with 

 flattened and adpressed cilia. 



1. Front tarsi of male with dilated joints oblong ; 

 stigmata of last two dorsal segments of abdomen not, 

 or but little broader than the preceding ; outline of eye 



notched by the free margin of the front of head . . . COLTMBETINA. 



2. Front tarsi of male with dilated joints forming a round 

 disc ; stigmata of the last two segments of abdomen 



enlarged ; circular outline of eye not interrupted . . Dttiscina. 



