24 Bulletin American Museum of Natural History [Vol. XLII 



Abdomen with ten distinct segments and narrowed caudally. The first eight 

 tergites similar and each covered by a dorsal plate, the posterior angles and margin 

 of which are rounded; a transverse row of setae at the posterior margin and a fairly 

 prominent seta at each side. Eight pairs of small round spiracles present and each 

 situated in the spiracular area just inside and anterior of the lateral seta?. Pleural 

 groove distinct. Each segment with a ventral plate less chitinized towards the 

 anterior and with seta? arranged as on the dorsal plate. Ninth segment similar to the 

 preceding ones, except that it is slightly longer and the irregular row of setae are 

 absent at the posterior margin, inside the insertion of the cerci. A pair of two-seg- 

 mented, divergent cerci arise from the posterior margin of the ninth tergite, their 

 points of insertion almost contiguous. First segment of cercus, longer than the anal 

 or tenth segment, chitinized, constricted slightly in the middle and with several long 

 distal setae besides other shorter ones; second segment slender but not tapering; 

 less than one-half the first segment in length and bearing a single, long, terminal seta. 



Anal segment cylindrical, longer than wide, banded with chitin, the tip membra- 

 nous, a row of short setae around the caudal border of the band and a terminal pair of 

 stout,, recurved hooks directed downward. 



Hydr^ina Kugel 



Only one species, H. pennsylvanica, is found in the vicinity of 

 Cayuga Lake. One cannot fail to recognize the members of this genus 

 because of their long, slender maxillary palpi and almost invariably 

 hexagonal pronotum. 



Hydreena pennsylvanica Kieswetter 



Plate IV 



The life history of this minute water scavenger has never been 

 described. The small, elongate beetles are often overlooked unless one 

 collects especially for them. They are found either in flowing or stand- 

 ing water and occur most frequently where the shore is muddy or 

 gravelly. Specimens were collected throughout the spring and summer 

 at the same special collecting grounds but they proved to be most 

 numerous in April and May. Once located, the same spot will yield 

 specimens for the rest of the season. The stock pool for 1915 was one 

 of the railroad pools, east of the tracks of the Lehigh Valley Railroad, 

 Auburn Division, and south of Fall Creek, where on April 14 over 

 forty were taken by washing out the mud at the shore-line. During 

 late August many of the beetles were observed crawling over stones and 

 pebbles where the water lapped the shore of Cayuga Lake near the 

 mouth of Taughannock Creek. Their most common associates are 

 Paracymus subcupreus, Ochthebius tuberculatus, Hydrochous squamifer, 

 and Cercyon ocellatus. 



