Idolocoris agilis Uhler is redescribed and a lectotype designated. Three new species of Dicyphus Fieber are described: confusus from Alberta, British Columbia, Colorado, and Idaho; similis from Alberta, British Columbia, Saskatchewan, Ontario, Quebec, New Brunswick, Nova Scotia, Newfoundland, New Hampshire, and New York; tibialis from Alberta, British Columbia, Colorado, and Montana, Left claspers of the four species are illustrated.