Length 5.3 to 7.7mm. As with other Helophorus the pronotum has characteristic zig-zag longitudinal grooves. It is pale brown to straw coloured with darker spots on the elytra.

The large size means it could only be confused with larger specimens of Helophorus aequalis which can reach 6.3mm. They share similar habitat preferences and can be found together. H. grandis has castellated 'teeth' on bottom edge of the last sternite (in H. aequalis these are much finer and more numerous).

• 5.3-7.7mm
• brown
• intercalary stria present (short row between first and 2nd stria)
• front of pronotum straight(ish) in the middle
• marginal teeth of last sternite deep and castellated (view underside of beetle)
• typically a wetland species

Freshwater habitats although it does fly and may be attracted to light.

All year round.

Widespread and fairly frequent in Britain.

Fairly frequent in Leicestershire and Rutland. There were approximately 190 VC55 records for this species up to March 2015.