Twenty-six species in five families of semi aquatic Hemiptera were collected in Wisconsin and as many as four more may occur. Keys to all of these species are provided along with notes on their distribution, abundance, and identification. Most species were distributed statewide, except that Gerris insperatus and Rhagovelia obesa were most common in the north, and Garris marginatus, Rhagovelia oriander, and Neogerris, Pheumatobates, hestone, were most common in the south. Metrobates, Neogerris, Rheumatobates, Trepebates, Mesovelia, and Rhagovelia apparently overwintered as eggs since adults were absent in the spring. Adults of other genera were collected from early spring to autumn
