This group of Dyticidce was first defined by Dr. Leach, and 
established as a genus in the 3rd volume of the Zoological Mis- 
cellany, where unfortunately, the name of Trogus is assigned 
to it, which had been applied many years before by Panzer 
to some of the Ichneumonidce ; it has therefore become neces- 
sary to supersede it, and Cybister (which is derived from the 
Greek) is not inapplicable. 
As the natural situation of our genus appears to be between 
Acilius and Dyticus (both of which have been figured and 
described in former parts of this work), we propose the fol- 
lowing arrangement for the commencement of the family, be- 
ginning with Acilius , which, from its depressed form, short 
tibiae, unequal claws, &c. is allied to Cybister ; after which 
follows Dyticus , commencing with D. latissimus Linn., and 
ending with D. angustatus Steph., which leads to Hydaticus , 
being more convex, and having the intermediate tarsi dilated 
at their base, a character possessed by Colymbetes , which will 
consequently follow. 
The few species at present known of our genus are widely 
dispersed, having been received from China, Tranquebar, the 
Mauritius, and North America. C. Rceselii has long been de- 
scribed as a native of Germany, France and Sweden, but it has 
never before been recorded as British ; and the only indige- 
nous specimen at present known is the female figured, which 
was found the 30th Sept. 1826, in a puddle at Walton, Essex, 
by J. Dane, Esq., who presented it to the gentleman in whose 
cabinet it is preserved, and through whose kindness we are 
enabled to present our readers with this fine and valuable ac- 
quisition. 
The difference of sculpture in the sexes is fully described 
in the generic characters : in colour they are very similar, the 
males are generally larger, and in our species they are black- 
ish beneath. 
The beautiful Hottonia palustris (Water-violet) accompa- 
nies the insect in the plate. 
