34 University of Michigan 



Hydrometridae 

 Hydro}nctra martini Say. Several specimens were collected 

 at a small pond at the base of Bald Tom dune, June 23 to July 

 26. Others were taken from the New Bufifalo marsh (June 

 30) and from a small pond in the Warren Woods (July 4). 



Gerridae 



Gerris rcmigis Say. Abundant on the Galien River in the 

 Warren Woods, and on all the small creeks which flow 

 through the dunes to Lake Michigan. 



Gerris marginatus Say. Abundant and widespread in Ber- 

 rien County. Specimens were collected at New Buffalo, the 

 Warren Woods, Harbert. the dune region, Bridgman, and the 

 Grand Marais. 



Gerris alacris Hussey.^" This species was taken in only one 

 locality, a small pond at the east base of Bald Tom dune, 

 near Sawyer, where specimens were taken July 19 and July 

 26, 1920. This pond is about sixty yards in length, compara- 

 tively narrow, roughly crescent-shaped, and has a maximum 

 depth of five or six feet. On the west it is bordered by the 

 steep slope of the bare dune ; on the north it is fringed with 

 willows growing on a narrow strip of damp sand ; and on the 

 east and south it is shut in by a small stand of elms and other 

 trees. A small brook connects this pond with another larger 

 one a short distance to the north. The water is turbid and 

 supports an extensive growth of aquatic vegetation in which 

 the cow-lily (Nyiiipluca adz'cna) is conspicuous. 



This Gerris was the most plentiful member of the genus 

 here on these dates, and even at first glance it was recognized 

 as distinct from its congeners. I have subsequently taken it 

 at Ann Arbor. 



^'^ Psyche, 28, p. 11, 1921. 



