Key to species of the Belostoma triangulum group

1 Lorogenal cleft with a conspicuous fovea (Fig. 1B); prosternal keel not prominent, projecting forward; dorsal arms of phallosoma wider at the base than at the apex (Fig. 3A)....................................................... B. bachmanni

- Lorogenal cleft without fovea; prosternal keel prominent (Fig. 1A), not projecting forward; dorsal arms of phallosoma subequal in width at the base and apex (Fig. 3D).......................................................... B. triangulum