Key D. Species of Telmatophilus

1. Body length 2.5–3.0 mm; meta-tibia of male with an external flange-like expansion at the base; male with a deep oval pit at the apex of the fifth (last) visible abdominal ventrite .................................. Telmatophilus americanus

– Body length 1.9–2.6 mm; meta-tibia of male without any flange-like expansion; male with a feeble depression at the apex of the fifth (last) visible abdominal ventrite..................................................... Telmatophilus typhae