Key to the British Gyrinidae

For more information on this family, click HERE.

1.

Upper surface finely pubescent. Elytral puncturation random.

Upper surface glabrous. Elytral puncturation arranged in rows.

2.

Scutellum with a keel at base. Pronotum with a central longitudinal ridge.

Scutellum simple. Pronotum without a central ridge.

 
3.

Ventral surface entirely pale, dorsal surface bicoloured; metallic puncture rows obvious against dark interstices.

 

Ventral surface mostly dark, dorsal surface unicoloured.

4.

Middle and hind claws back.

Middle and hind claws pale, same colour as the legs.

 
5.

Elytral margin parallel or narrowed towards the apex.

Elytral margin broadened slightly towards the apex.

 
6.

Pronotum and elytra with distinct microsculpture; dull.

Gyrinus opacus

Pronotum and elytra smooth or with only indistinct microsculpture; shiny.

 
7.

Form narrow; elytra only slightly broader at the middle than at the base.

Form broader; elytra rounded and distinctly broader at the middle than at the base.

 
8.

Mesosternum pale against the surrounding sclerites.

Mesosternum black.

Gyrinus caspius
Gyrinus paykulli
 
9.

Transverse series of punctures towards the elytral apex distinctly weaker and often obsolescent compared to those in the adjacent striae.

 

Transverse series of punctures towards the elytral apex as strong as those in the adjacent striae.

10.

Elytral interstices with tiny punctures evenly spread across the interstices.

Gyrinus distinctus
 

Elytral interstices with three or less rows, which may in places be confused, of tiny punctures.

Gyrinus natator

or

(Dissection needed)