1920] Richmond, Studies on the Biology of the Aquatic Hydrophilidce 65 



eight at the posterior margin, counting the two corner ones; two just posterior and 

 slightly lateral of the two middle styli of the anterior margin; a transverse row of four 

 in the middle, the outer two a little anterior the inner pair; a few other inconspicuous 

 styli are present. 



Mesonotum and metanotum with a transverse row of two styli. Inner spur of 

 metatibia not very prominent. All tarsi not ending in a spine but blunt and tibiae 

 not spinous on the outer side; first to seventh abdominal tergites inclusive with a 

 transverse row of six styli; second to seventh pleurites each with a stylus; eighth 

 tergite semicircular, the posterior rounded margin bearing two styli; ninth segment 

 with a pair of tapering, fleshy cerci, longer than the ninth tergite (0.62 mm.) extending 

 caudally and diverging slightly. Externo-caudal angles of ninth sternite obtuse and 

 not very prominent. A pah of appendages arise from between the eighth and ninth 

 sternites and extend caudally on either side of the median line to the base of the cerci 

 and closely appressed to the ninth segment. Spiracles oval, prominent, second to 

 sixth visible. 



Helochares normatus LeConte 



Zaitzev, 1908, placed this species under Chasmogenus but questions 

 it. The egg-case, as well as the larva, closely resembles H. maculicollis 

 and it doubtless belongs under this genus. 



Philydrus 1 Solier 



In our fauna there are six members of this group and, although they 

 are apparently close in general structure, yet coloration, size, and form 

 play such an important part in their separation that they are easily 

 determined after one has had a brief introduction to the systematic 

 study of them. The most easily confused member is doubtlessly P. 

 per plexus, which may be easily placed as Cymbiodyta fimbriata unless 

 the genus is first assured. In size the species range from P. ochraceus 

 (the smallest), P. nebulosus, P. perplexus, P. hamiltoni, and P. ductus to 

 P. consors (the largest). The first two species named are very abundant 

 near Ithaca while the latter three are comparatively rare, although one 

 mud-pocket yielded about a dozen specimens of P. consors in company 

 with a larger number of Cymbiodyta fimbriata when the writer was col- 

 lecting in late June. 



The life history of this genus has been studied only in Europe, 

 where Schiodte reared P. testaceus Fabr. and figured 2 the stages in his 

 well-known work. The writer has been able to compare this life history 

 with that of some American forms which he has reared. 



Zaitzev, in his ' Catalogue des Coleopteres aquatiques families des Hydrophilid® ' gives Enochrus 

 as the valid name, claiming that Philydrus is preoccupied, but the author feels convinced that Philydrux 

 Bho lid stand. PhUydi u? was originally used without the "h." 



The figures by Schiodte are not entirely accurate. The labro-clypeus should be oblique and the 

 left mandible was evidently incorrectly drawn. 



