Melanacanthus margineguttatus Distant and Riptortus macleani Schaffner (both Alydinae) and Leptocorisa oratorio (F.) (Micrelytrinae: Leptocorisini) are recorded from Guam, the last for the first time. Melanacanthus and M. margineguttatus are redescribed; Melanacanthus is compared with other alydine genera; R. macleani and L. oratoria are compared with related species; and some biological notes from the literature are discussed.