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Whirligig Beetles - gyrinus substriatus

What's in the water?

Whirligig beetles

An introduction to aquatic invertebrates in Rockingham Forest 

by County Recorder, Kevin Rowley

With many ponds, ditches and streams within the Rockingham Forest Vision area, there is a great variety of aquatic invertebrates many of which you never see. They can be weird and very wonderful as well as sometimes rare.

I would encourage you to stand and peer into the water and look for movement either on or under the surface and it is amazing what you will see.

On the surface

Looking for wildlife in Fineshade Brook

If you are looking on the water surface then you are most likely to see  water bugs.

 

Pond skaters are predatory bugs that run on the surface and chase any type of prey, which they capture with their modified front legs. They tend to be in small family groups.

 

There are 10 species in the UK and are very similar, but if you see one with an orange patch just below the head they are possibly Gerris thoracicus which likes small or newly created ponds.

Pond Skater Gerris thoracicus - Tony Cook

Looking for wildlife in Fineshade Brook

A pond skater
Gerris thoracicus -
Photo: Tony Cook

A water cricket
Velia caprai

Photo:  Tony Cook

Water cricket Velia caprai - Tony Cook

Also on streams and ditches keep an eye out for water crickets. These are smaller but have thicker more powerful legs so that they can run upstream. There are two species that are very difficult to tell apart but one prefers muddy bottoms and muddy banks (Velia caprai) and the other more stony/rocky substrate (Velia saulii). Both occur in the Rockingham Forest area. 

Backswimmers are easy to see as they come up to the surface for air and lie just under the surface with their backside out of the water capturing some air before diving back down again. There are 4 species in the UK all of which can be found in the same ponds in Fineshade Wood for example

A backswimmer
Notonecta sp.
Photo via iRecord, Thom Lyons

Whirligig Beetle Gyrinidae sp. Ai-Lin Kee

Other regular surface dwellers are the aptly named Whirligig Beetles which can often be seen in large groups whirling around on top of the water. There are four species that are likely to be found on the ponds or streams that look very similar. However they all have four eyes, two which are looking upwards and two which are looking underwater. This makes them awesome hunters that quite literally have eyes in the back of their heads.

Whirligig beetles
Gyrinidae sp. -
Photo vis iRecord, Ai-Lin Kee

Under the surface

Cherrystone Beetle

Hyphydrus ovatus

Photo: UK Beetles website

Cherry stone Beetle (Hyphydrus ovatus)

If you can see under the surface look  both for those that are swimming and also for small movements on the bottom or at the edge of reeds.

 

Water beetles are seen swimming around in the water column. One of those is the Cherrystone Beetle (Hyphydrus ovatus). This, as its name suggests, is a red, round beetle around 5mm and can be common in the mid-successional ponds.

At the other end of the scale are the Great Diving Beetles. There are 6 species in the UK with 3 likely to be found in the Rockingham Forest area.  One feature is the colour of the belly that you don’t always see clearly. There is the Black- bellied Diving beetle (Dytiscus semisculatus), the black -and -yellow-bellied “The WASP” (Dytiscus circumflexus) and the orange-bellied Common Diving Beetle (Dytiscus Marginalis). They are very effective apex predators with big jaws and fast swimmers.

Black-bellied Diving Beetle

Dytiscus semisculatus

Photo: Jeff Blincow

Dytiscus semisculatus by Jeff Blincow
Southern Hawker Dragonfly Nymph Photo: Kevin Rowley

Dragonflies and Damselflies are aquatic, living under the water in their larval stages and, while they only have short adult periods on the wing, they are always present as nymphs in water bodies. They need close inspection to identify to species but  they are fascinating to watch. They have an extendable jaw called a labium which can shoot out and catch prey - scary! Dragonflies also are able to take in air to their body and in times of escape or attack they can shoot it out and effectively use it as jet propulsion.

Southern Hawker Dragonfly Nymph Photo: Kevin Rowley

Rarities

The rarities are often small, inconspicuous species that often get overlooked. They can also be habitat dependant and therefore need care to monitor and manage the habitat for them.

 

One is Hydrochus elongatus. This is a near-threatened, small, crawling water beetle that lives in shallow, still water, that is usually well-vegetated, often in reedbeds over clay.

 

Its stronghold is the ponds, lakes, reservoirs and gravel/clay pits along the Nene Valley. This habitat has increased over recent times but the restoration of clay ponds with reed beds will definitely benefited this little beetle.  

A small water beetle  Hydrochus elongatus

To learn more please visit my website:  Northants Water Bugs

About Kevin Rowley

Over the past 15 years Kev has taken on County Recorder for Water Bugs and as national verifier on iRecord for Water Bugs and Water Beetles. Kev has spent much of his free time surveying wet places and meticulously identifying species and compiling records. He has also created an amazing detailed website on Northants Water Bugs including a species atlas, species portraits, an identification guide and  a new identification key. Kev lives in Duston and has a day job as Head of Software testing for Barclays Mortgages  - he is avidly looking forward to a time when he can spend even more time in wet places!

Kevin Rowley

Interested in invertebrates?

The Northamptonshire Invertebrate group runs field trips throughout the county and is looking for keen invertebrate recorders to come and join them. Beginners looking to learn about recording are also welcome to attend and develop their skills.

 

More details about the group here

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