972 (In Aquatic Caniiiorouii Cohoptera or Dytiscida. 



cliflerent condition to what wu find existing- in tlie predaceous Culeoptera, yet 

 there is reason to think that the coxse of these beetles are now smaller than they 

 were formerly, and that the condition of these parts in the insects we now call 

 Carabidio and Dytiscidiu may in far distant periods have been more similar to 

 what still exists in Blatta than is at present the case, and this will afford a clue to 

 the modes of growth that have preceded the present structural conditions : and 

 ultimately enable us to determine which of these are higher, which lower. 



The Haliplidse were formerly included among the Dytiscidaj, but their sejiaratiou 

 was suggested by Lecoute, and has been effected by C. J. Tliomson. Schaum in- 

 cluded them again in the Dytiscidee, remarking however (Insect. Deutsch. I, pt. '1, 

 pp. 9 and 10), '"that their legs are not swimming legs in shape, but only by 

 ciliation, and that they differ so much from the true Dytiscidie in the insertion of 

 the antenna? and the number of their joints that they could be erected into a 

 peculiar family, were it not fur the fact that Pelobius existed to unite the two 

 groups together." This latter remark of Schaum's I fail to understand : There 

 is no sense in which Pelobius can be correctly said to unite {o\ be a connecting link 

 between) the Haliplida? and Dj-tiscidte. It is true that it is doubtful whether 

 Pelobius should be included in the Dytiscidre at all, but it does not approximate 

 in the slightest degree to any of the special peculiarities of the Haliplida? ; and it 

 does not follow that because neither of them is Dytiscida3 therefore they are allied. 

 To include the Haliplidte in one family with the Dytiscida?, while these latter are 

 kept separate from the Carabida? is certainly an erroneous course, for the Haliplidje 

 not only fail to possess the peculiar coxa of Dytiscida?, but have in fact that part 

 modified from the Carabideous ty^je of structure in a totally different direction 

 from what the Dytiscid.'e have, and cannot therefore be classed with these. It is 

 true they exhibit the important peculiarity of glabrous antenna;, v.nd that they 

 share this in cumiuuii Avith the Dytiscida?, but this, althotigh it may be a sufficient 

 reason for separating them from the Carabidte, is not of itself enougli to warrant 

 their union with the Dytiscidje. While should the glabrous antennas be considered 

 insufficient (when this part lias been sufficiently studied in the Carabida?), to 

 warrant their isolation, then they must be classed as a group of Carabidte,^' but not 

 with the Dytiscidie. 



The Dytiscidte show but little approximation to any other beetles, besides those 

 already alluded to. The other two families of water beetles, Gyrinidse and 

 Hydrophihd;!}, are so distinct that no one in later times thinks of classifying 

 them together. 



* I may here notice, though foreign to my immediate subject, that the Haliplidse dilTcr from the 

 CarabidcE, in tlie structure of the front of the head, and in the insertion of the ant-jnn», and approach in. 

 these respects to tlie Cicindelidie. 



