102 The Ohio Journal of Science [Vol. XVII, No. 4, 



or a distinct median, longitudinal groove while the Nearctic 

 forms have the head with two longitudinal grooves, converging 

 anteriorly, and a median ridge between these grooves. The 

 members of the genus are all very small insects, being two 

 millimeters or less in length. Dimorphism seems to be char- 

 acteristic of the genus — macropterous and brachypterous forms 

 occurring in the same species, the latter form having only short 

 wing-pads that vary somewhat in size in the same species and 

 in different species. 



The habits of those species of Merragata White that I have 

 observed indicate that they are dwellers in still and stagnant 

 waters. Their favorite haunts are secluded coves of lakes, 

 ponds, and swampy pools, where the water is shallow, and where 

 there is an abundant growth of aquatic plants. I have rarely 

 seen them on the damp ground near the water's edge. The 

 Merragatas are aquatic pedestrians, capable of standing, 

 walking, and running upon the surface of the water, their entire 

 body being covered with a velvety pile which effectively sheds 

 the water and prevents them from becoming wet. They can 

 move forward or backward, but the usual mode of progression 

 is a steady forward movement, all three pairs of legs being used 

 in locomotion. I have often found them on Lemna, Nymphcea, 

 and various other aquatic plants. It is not uncommon to find 

 them on the underside of floating leaves, or even among the 

 roots of floating water plants. When submerged in the water, 

 the insects are surrounded by a film of air which enables them 

 to sta}^ beneath the surface film for a considerable period 

 of time. In an ac^uarium I have often watched them standing or 

 walking for a period of a half hour or a little longer on pieces of 

 cork or plants that were beneath the water. Occasionally, 

 they will walk down the sides of the glass aquarium beneath 

 the surface of the water, and when the water is shallow, they 

 will walk across the bottom and come up on the opposite side. 

 Nothing seems to be known of their food habits and life history. 



KEY TO THE GENERA OF AMERICAN HEBRIDAE (nAEOGEIDAE). 



AntenncC consisting of four .segments, the minute segment at the base 

 of the third being counted as a part of the third segment. . . . 



Genus Merragata White. 

 Antennse consisting of five segments, the minute seginent at the base of 



the third being counted as a part of the third segment 



Genus Hebrus Laporte. 



