Hydroglyphus flammulatus, is a species of predaceous diving beetle found in India, Sri Lanka, Pakistan, Thailand, Cambodia, China, Taiwan, Korea, Myanmar, Bangladesh, Indonesia, Vietnam, and Nepal.

Fourth segment of the protarsi and mesotarsi are much reduced, and hardly visible.

Latero-basal plica on pronotum not continued on elytra.

[3] The sutural striae in elytra are complete but less distinctly carved.

Elytral striae and a transverse groove behind the eyes are missing.