Insects. 4919 



varieties of our commonest species ; and occasionally different species 

 stand under one name, or the same species is located in even different 

 genera : with such incorrect data, it is scarcely safe to rely upon any 

 of the localities, excepting those which are distinctly stated to have 

 been communicated by the captors. 



Having for many years kept a journal which was incorporated 

 annually in catalogues of all the orders, extending to four quarto 

 volumes, specifying the localities and dates of capture of each 

 species, as far as the knowledge of my friends and my own ex- 

 perience enabled me, I can speak with tolerable confidence, except 

 in some instances where the names have been transposed from the 

 late unsettled state of our nomenclature ; but with regard to the rarer 

 species, the data have been recorded by me with the greatest care, 

 and may therefore be depended upon. 



Accuracy is most essential in every branch of Natural History, for 

 errors once in print become permanent, and are not unfrequently 

 widely spread by writers copying one another, instead of referring to 

 the original source. There are innumerable instances of this nature 

 bearing on my own labours, and as it is now thirty years since the 

 first genus of Dytiscidae was illustrated in my ' British Entomology,' 

 and many entomologists in the country may not have access to the 

 sixteen volumes, I shall refer to the nine genera of that family, with 

 the figures given, adding such corrections as have been considered 

 necessary by subsequent investigations. I hope also that the 

 localities I shall furnish may render the chasse of the collector 

 satisfactory and successful. 



According to my arrangement, I commence with 



Haliplus, Lair. 



1. H. elevatus, Panz. In September, 1810, the Rev. J. Burrell 

 took me to a little clear running brook at Letheringsett to show me 

 the locality of this pretty and at that time rare species ; we found in 

 company with it Colymbetes vitreus and C. maculatus. These are all 

 more abundant in May. 



2. H. ferrugineus, Payk. f Curt. Brit. Ent. pi. 730. This is the 

 D. fulvus of Fabricius ; " Paykull however gave the name of ferru- 

 gineus to this Haliplus before Fabricius and Marsham noticed it," 

 vide Brit. Ent. fol. 730. 



Cnemidotus, ///. 



3. C. caesus, Duft. ; D. flavicollis, Marsh. I remember taking this 

 curious insect in the vicinity of Norwich, but subsequently I used to 



