﻿1870]. 



253 



ON HYDROBIUS AND ALLIED GENERA. 

 BY D. SHAEP, M.B. 



Whilst engaged in the examination of our Hydrophilidce, I have 

 become impressed with the fact that the species of the genus Hydrobius 

 (as understood by Mulsant, Lacordaire and Duval) are very discordant 

 in facies or appearance ; and, acting on the impression so gained, I 

 have made careful examination of the external anatomy of these in- 

 sects and the allied genera. The result is that I have found that an 

 arrangement of the species of these genera, in accordance with their 

 facies, would also be a natural one as regards their anatomical and 

 generic characters. The divisions I think it will be well to adopt 

 are exactly in accordance with those proposed by Thomson in his 

 " Skandinaviens Coleoptera." As, however, the characters given for 

 these divisions by that talented author are in some respects incomplete, 

 and as his genera have not been yet adopted in such catalogues as have 

 been published since his work appeared, I have thought a sketch of the 

 characters of these genera may be useful to entomologists. I am not 

 acquainted with the exotic species of this family ; but hope they will 

 help to prove the validity of the divisions here adopted. 



1. Hydkobitts, Leach. 



1 — maxilla and max. palpus of Hydrobius fuscipes. 

 la— labium of ditto. 



2 — maxilla and max. palpus of Helochares lividus. 

 2a— labium of ditto. 



8 —maxilla and max. palpus of Philhydrus melanocephalus. 

 3a — labium of ditto. * 



4 — maxilla and max. palpus of Enochrus bieolor. 

 4a — labium of ditto. 



5 — maxilla and max. palpus of Parcacymus aineus. 



6 — ditto ditto Anaccena globulus. 

 6a -labium of ditto. 



Of an oblong- oval 

 form. Mesosternum 

 carinated in the mid- 

 dle, in front of the 

 intermediate coxge. 

 Tibiee strongly spinu- 

 lose. Maxillary palpi 

 moderately long, the 

 third joint shorter 

 than the second or 

 fourth, which are of 

 about equal lengths ; 

 labial palpi mode- 

 rately long and mode- 

 <?rrately stout, the se- 

 cond joint longer than 

 the third. 



Two British 

 species ; fuscipes 

 and oblongus. 



