Large diving beetles found during pond conservation work.
No interactions present.
Yes, these are definately Dytiscus beetles - they're quite distinctive, at least to genus! The beetle on the right is a male, with smooth elytra, and the female is on the left, with the ridged elytra - the ridging extends all the way to the end of the abdomen, so they're not D. demidiatus (assuming they're both the same species - never a great idea!)
D. circumflexus is primarily a brackish-water species, and D. lapponicus is found in stony-edged waterbodies in Scotland, which leaves D. marginalis and D. circumcinctus as the two main possibilities - circumcinctus is a lot rarer than marginalis,and there are a couple of other pointers to these being marginalis, primarily the placement and thickness of the yellow bordering, but the key feature is underneath, the shape of the attachment of the hindmost pair of legs, so we can't really get any further than Dytiscus sp for definate!
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Ta for the info, rimo - pretty much where I'd got to - if anyone's particularly interested in water beetles, there is a Field Studies Council key by L.E.Friday (1988) in Field Studies Vol 7 (1): 1-152. I think it was reprinted as a separate AIDGAP guide but this appears to be out of print (certainly it isn't currently on the website http://www.field-studies-council.org/publications/aidgap.aspx
The Water Beetle key in Field Studies was reprinted as a separate AIDGAP publication (Friday,L.E. 1988 A Key to the Adults of British Water Beetles ) but this is now out of print, though it does turn up on book dealers lists now and then. As I understand it, the whole publication is being revised and expanded at present, though I don't know of any anticpated publication date.
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