56 Bulletin American Museum of Natural History [Vol. XLII 



three, however, shows an indication of another tooth. The mandibles 

 have three inner teeth but the most proximal tooth of each is very small. 

 The cerci of the pupa are tapering, fleshy, and about equal to the 

 seventh to ninth abdominal segments inclusive. The motory styli of 

 the abdominal terga are four in number and each pleurite bears one. 



Helocombus Horn 



Only one species, H. bifidus, represents the genus over the entire 

 world. In the field it is often confused with Hydrobius fuscipes and 

 differs principally in its longer maxillary palpus, the last segment of 

 which is shorter than the penultimate. It might be taken for Philydrus 

 ductus, a common associate, but the elytra of the latter is not striate. 



Few specimens have been captured in the immediate vicinity of 

 Ithaca and it is only by chance that one collects them. However, they 

 proved to be rather plentiful during May in the pools bordering the 

 Ringwood Road at the source of Cascadilla Creek. Their life is spent 

 under leaves at the edge of the ponds. The life history is unknown but 

 the stages are probably close to Cymbiodyta. 



Cymbiodyta Bedel 



Superficially this genus is very close to Philydrus but is easily sep- 

 arated by the transverse mesosternal carina, in contrast with the longi- 

 tudinal keel of the latter. The presence of only four segments in the 

 middle and hind tarsi bears additional testimony of the validity of this 

 genus. In New York we have four representatives of this group, namely, 

 C. Jimbriata, C. blanchardi, C. lacustris, and C. rotunda. Of these, the 

 two former have been collected in the vicinity of Ithaca in fairly large 

 numbers, while there is doubt as to the presence of the latter two, al- 

 though one specimen 1 of lacustris (?) was reported in 1909 by Professor 

 J. C. Bradley. The life history of none of the species has been worked 

 out. 



Both C. blanchardi and C. fvmbriata are found in the same environ- 

 ment and are often taken together. The easiest method of collecting 

 seems to be taking the debris, including leaves, sticks, and decaying 

 matter which accumulates near the shore-line, and washing the beetles 

 out by placing and shaking the trash in deeper water. The beetles, as 

 with other Hydrophilidaa, rise to the surface and can easily be picked up 

 by the fore finger and placed in the collecting jar. Often they are so 



iThe specimen is not at hand so I was not able to verify its determination as such. 



