Spangled diving beetle (Graphoderus zonatus)

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Spangled diving beetle
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Spangled diving beetle fact file

Spangled diving beetle description

KingdomAnimalia
PhylumArthropoda
ClassInsecta
OrderColeoptera
FamilyDytiscidae
GenusGraphoderus

This beetle has the appearance of being sheathed in gold, but only, it seems, when photographed under certain lighting conditions. The edges of the body are outlined with black.

Size
Body length: 13 - 15 mm
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Spangled diving beetle biology

This is a predatory species, like all other British water beetles. Adults emerge at the end of June from pupae at the base of tussocks of rushes. The larvae feed on other aquatic insects and their young, such as water boatmen. Adults can fly and they may spend winters away from water altogether, whereas the larvae prefer open water.

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Spangled diving beetle range

The spangled water beetle has two subspecies where it occurs in Europe. One variety G. z. verrucifer is found in the northern regions as far south as Italy. The subspecies that occurs in the UK ranges through central and southern Europe as far as Mongolia. The UK range is limited to just one site, Wolmer Forest in Hampshire. In the past, this species was misidentified as a related species G. cinereus, and given a range that included Norfolk and the Cambridgeshire and Huntingdonshire Fens.

You can view distribution information for this species at the National Biodiversity Network Gateway.
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Spangled diving beetle habitat

The spangled water beetle is found in several pools within Wolmer Forest, all of which vary considerably in depth, vegetation and acidity levels. The chief breeding area, however, seems to be concentrated in just one; Cranmer Pond. These pools have changed considerably over the centuries as a result of peat cutting, military activities and conservation work for natterjack toads.

In his collection of letters to Thomas Pennant and the Honourable Daines Barrington, published as 'The Natural History of Selbourne', the Reverend Gilbert White has left us with a description of Wolmer Forest and its ponds from around 1770. He describes the forest as 'without one standing tree in the whole extent', but more importantly he describes the ponds of Wolmer as 'stocked with carp, tench, eels and perch: but the fish do not thrive well, because the water is hungry, and the bottoms are a naked sand'. Today, these pools contain no fish at all.

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Spangled diving beetle status

Classified as Endangered in the UK.

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Spangled diving beetle threats

This species is threatened by the loss, or mis-management, of their only known UK habitat, and by pollution from a nearby pig farm. There is also the possibility that changes in the acidity levels of their ponds could allow fish to return.

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Spangled diving beetle conservation

The spangled water beetle is listed in the UK Biodiversity Action Plans, and included in English Nature's Species Recovery Programme. Because of the precarious nature of this species' survival in Britain, annual monitoring of the ponds at Wolmer has been carried out since 1993.

All the currently populated ponds are now part of a Site of Special Scientific Interest (SSSI) and managed jointly by English Nature and the Ministry of Defence. It is planned to excavate four new ponds within Wolmer Forest in the hope that the beetle can increase its numbers. There has already been an attempt at introducing the species into a suitable new area but without success. Future work will include finding out more about the exacting requirements of the beetle so that any further introductions will, hopefully, be more successful.

View information on this species at the UNEP World Conservation Monitoring Centre.
The UK Biodiversity Action Plan for this species is available at UK BAP.
There may be further information about this species available via the National Biodiversity Network Gateway.
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Find out more

For more information on conservation in Hampshire, see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Larvae
Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Pupae
Stage in an insect's development when huge changes occur, which reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
Subspecies
A different race of a species, which is geographically separated from other populations of that species.
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References

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Image credit

Spangled diving beetle  
Spangled diving beetle

© Roger Key

Dr Roger Key
Tel: +44 (0) 1845 567 292
key_r_s@yahoo.co.uk

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