Colymbetes fuscus
Colybetes fuscus 01-06-2008
The white objects on the wingcases are grains of sand.

The word fuscus means brown, dark. The first impression however is a light brown or beige waterbeetle with a faint green shining. But on the under side the beetle is black brown. Possibly the name givers thought this remarkable in comparison with other diving beetles that have a lighter coloured under side. Furthermore the neck shield is brown. On the picture below the dark under side is visible. The beetle on the second picture is a specimen of Rhantus suturalis, which is a smaller beetle that bears a strong resemblance. Both beetles are common, but do not have an English name.

Colymbetes side view
Colymbetes fuscus
Rhantus side view
Rhantus suturalis

This waterbeetle is common everywhere in Europe, yet it took years before I found it. This specimen was hidden in a small pool near a river, between tight masses of alga and water plants. The smooth, flat body makes it easy for the beetle to shoot away in such hideouts. Maybe that's why it's to fast for the dipping net. This time I used an apple sauce sieve, which can be pulled through dense water plant forests, and suddenly this beetle was in it, nervously crawling and jumping.

The beetles of the genera Colymbetes and Rhantus are placed in the Colymbetinae subfamily of the large family of Dytiscidae (diving beetles). Here is a picture at the same scale of a Rhantus suturalis that was in the same pond. It seems both species have light brown wingcases, but a closer look reveals that the basic colour is a brown yellow, over which a dense black pattern lies. On Colymbetes this is a network of black, transversal grooves, while on Rhantus it's made of black sinuosities.

Colymbetes and Rhantus 01-06-2008
Colymbetes fuscus - Rhantus suturalis
Colymbetes and Rhantus, wing case detail
Colymbetes fuscus - Rhantus suturalis

Other genera within the Colymbetinae are Agabus and Ilybius. These are nearly all black beetles. Agabus bipustulatis is very common in Europe.

colymbetes under side

The under side of Colymbetes fuscus shows a dark contrast with the light yellow rims of the wing cases (epipleura). Click on the picture to view some detail. This specimen is a male, recognisable by the broadened front and middle legs with adhesive discs.

front and middle tarsi of Colymbetes fuscus
front leg - middle leg

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All pictures on this site were made by Gerard Visser (Aadorp, Netherlands), unless stated otherwise. All rights remain with him. These pictures may not be used for purposes any other than private viewing or printing. Do NOT hardlink to these pictures or place them on other websites without the author's approval. Should you need them for purposes which include third parties, you must ask the author permission by e-mail. People, who want to use this pictures for exhibitions or publications or educative material are much encouraged to do so, after approval as mentioned and giving the normal credits.
© G.H. Visser 03-06-2008
rev. 03-05-2022

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