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Section E


Dytiscus sp.

22.0-32.0 mm

Long filliform (thread like) antenna

racing green coloured body with lighter yellow markings

Elytra may have deep ridges in females, or lightly punctured in males

February - December


ID Features

Large ovate beetles with lighter bands on the pronotal margins.

There are 6 similar species in the UK.

I recommend using

This key by Adrian Chalkley

Taking Photos


Dytiscus species require a photo of the underside with a clear focus on the hind coxal processes as the shape and colour is important for species-level identification. In addition, a good dorsal photo that has the front and hind margins of the pronotum, as the relative thickness of the bands can also be a good ID characteristic. This is good practice for all water beetles if you are not sure!


Dytiscus circumflexus​ 



An ideal underside photo showing the yellow underside colour and hind coxal process shape (Right)

indicative of Dytiscus circumflexus. Credit Gary Lowe


Dytiscus circumcinctus 



Dytiscus circumcinctus​ Credit Mike Southall


Dytiscus marginalis 

Hydrophilus piceus  
Colymbetes fuscus
Ilybius fuliginosus

Colymbetes fuscus


ID Features


15.0 - 17.0 mm 

head black with lighter labrum and markings above eyes​

dark transverse reticulation on a light brown/olive coloured elytra

legs orangy brown

All year round




Transverse reticulation on the elytra is a key ID characteristic for this species and can be viewed easilly using a 10x hand lens

combyletes bill unwin.jpg


Transverse reticulation. Bill Unwin 2017

Ilybius fuliginosus


ID Features


10.0-11.5 mm 

Narrow oval body


Pronotum and Elytra with two very well marked pale stripes (pictured)

Bronzy head with a paler front (Labrum)


Antennaepalpes pale brown/orange


Front legs usually paler than the mid and hind legs

Jan - Nov




Superficially, this looks similar to the much rarer, larger, and heavier set Cybister lateralimarginalis, Which has only been found 4 times in Britain, although found more frequently in continental Europe

Hydrophilus piceus  

The Great Silver Diving Beetle is one of our largest beetle species in the UK. 

Instantly recognisable from the other oval-shaped diving beetles due to their short, distinctly clubbed antennae, elongate shape, and size.

34.0-48.0 mm

Massive scutellum 

Body Black upper side with green/purple luster

Short clubbed antennae

long red maxillary palpi (twice as long as antennae)

red antennae and maxillary palps

February- December

Local in SW & E England & S Wales


ID Features

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