Contacyphon coarctatus

This genus was formerly known as Cyphon and many references have this species listed as Cyphon coarctatus.

Like the scarcer Contacyphon palustris, this species differs from most other Contacyphon in having 3-4 faint ridges along the elytra, and unlike the palustris I had identified shortly before examining my first coarctatus, these ridges were reasonably easy to see.

Like palustris, the male aedeagus has apical processes including claws, the total length of which is about equal to the base on coarctatus and much smaller on palustris. One claw was damaged during the preparation but you can also see that the remaining one points inwards whereas in palustis they point outwards.

male Contacyphon coarctatus showing close up of the elytral ridges, its aedeagus (ventral section at two angles and dorsal section), sternite 9 and tergites 8 & 9, North Elmham Cathedral Meadows (Norfolk, UK), 27th May 2021

On this occasion I found a female Contacyphon with the male, swept together from Broom. Like the male (and unlike the palustris I found in the same area in July), this had strong elytral ridges that were easy to see. I naturally assumed it would be another coarctatus, and on a cursory look at the 8th sternite it appeared to match the diagram for this in Duff (and not palustris). The pair of sclerotised lines were evenly curved, their tips converging, broadest before the tips. However after setting it on a microscope slide it looks different, and now resembles the diagram in Duff for palustris, the tips diverging after they have converged and broadest at the tips. So now I'm not sure - has it's appearance changed as a result of gentle compression when applying the cover slip (in which case you've got to wonder how useful this character is as an ID feature) or did I not look at it carefully enough at first, and it is in fact a female palustris caught together with a male coarctatus? Answers on a postcard (or email)...

presumed (?) female Contacyphon coarctatus showing close up of the elytral ridges and sternite 8, North Elmham Cathedral Meadows (Norfolk, UK), 27th May 2021

This was one of 2-3 similar beetles beaten out of Sycamore. It was a lively thing when I was trying to photograph it and when I placed the pot over it to stop it escaping I unfortunately caught the back of the beetle, damaging the elytra and squashing the abdomen. After this incident the median lobe projected out of the tip of the abdomen which did at least enable a swift identification (although I did check by removing the lobe completely for a clearer view).

male Contacyphon coarctatus showing close up of the elytral ridges and median lobe, Wendling Beck Environment Project (Norfolk, UK), 7th May 2023

This one was beaten of Blackthorn beneath an Pedunculate Oak tree.

male Contacyphon coarctatus showing median lobe, County School Station, North Elmham (Norfolk, UK), 22nd May 2023