Acilius sulcatus

A large water beetle with considerable colour variation. Although it is a distinctively marked species, there are some very similar species and care is needed with identification. Length 15-18mm, broad oval shape. Pronotum pale with two transverse dark markings. Sexually dimorphic - males elytra smooth smooth but with four broad longitudinal and densely pubescent grooves delimited by raised ridges in females. Hind femora with dark markings in inner half (c.f. A. canaliculatus - hind femora are entirely pale). 

Temporary and permanent water bodies such as ponds and streams etc. A.sulcatus is able to fly it is not restricted to a single body of water. It is found in water bodies with high and low levels of vegetation showing no preference between the two.

All year round.

Widespread and fairly frequent in Britain.

Fairly frequent in Leicestershire and Rutland.