28 Bulletin American Museum of Natural History [Vol. XLII 



In gathering the species, one finds them most frequently in company 

 with Ochthebius, Hydrcena, Helophorus, Anccena and Paracymus but a 

 great deal harder to locate, with the possible exception of the two first 

 named. They seem to cling more tightly to the vegetation at the shore- 

 line with their rather powerful claws. Standing water with gravelly 

 bottoms and little vegetation or muddy pools seem to be their most 

 common habitat. About fifty were taken the latter part of August 1916 

 in a lagoon west of the Cornell Biological Field Station. The waters 

 at that time of the year are filled with Ceratophyllum (hornwort), 

 Spirodela (duckweed), and Elodea, while cat-tails abound, taking root 

 in the muddy bottom. Hydrochous was procured at the water's edge by 

 washing the mud away from the roots of the cat-tails. They came to the 

 surface immediately and, although very slow in action, they would 

 quickly become submerged by grasping the vegetation with their claws 

 unless washed out in deeper water. When their station, which seems to 

 change each year, is once located they may be captured in large numbers 

 but, otherwise, only scattered specimens are usually taken. • A single 

 specimen of H. scabratus was procured in Dwyer's Pond by sweeping the 

 submerged Elodea. When the imagos were placed in the aquarium they 

 immediately sought the under sides of some stones, below the water, 

 but when it was placed in the sun they soon came up, seeking the sunny 

 side. A few days later they were observed eating holes in decaying 

 leaves of moneywort and Marsilea, leaving only the tough veins. 



The life history has not been described and it has proven to be of 

 particular value in explaining the phylogeny of the family. Although 

 the larva has a well-developed stigmatic atrium, yet its head and mouth- 

 parts are quite primitive. 



The laying season seems to be confined to the beginning of summer 

 weather, about the latter part of May and the first of June. From the 

 fifty imagos taken the latter part of August, not a single egg-case was 

 obtained. A number of the beetles were taken in copulo on May 10 but 

 no cases appeared until about May 23. A single egg was deposited at a 

 time and placed between two layers of closely applied silk. The cases 

 were fastened down to the alga? or rocks in the aquarium, either above or 

 below water, and held firmly by the flap and stanchions. One case of 

 Hydrochous sp.? was particularly well supplied with little stanchions. 

 The egg-case of this genus is apparently one step forward from the egg- 

 case of Hydrcenam. specialization. 



The larvae appeared through a rupture in the silk in about seven to 

 eight days. They were quite at home in the water and the manner in 



