Coranus aethiops in Nottinghamshire

Finally ... an end to Budby's Assassin Bug mystery
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On the 2020 Invertebrate News page, the story of a Coranus type Assassin Bug found on Budby South Forest in 2017 and the need for a male specimen was published. The potential importance of the find was unfortunately (as is often the case) not realised until viewing the resulting photographs of a female Coranus, with what seemed to have an obviously black underside. So to bring the story up to date, it is probably best to give those not aware of this story, more of an insight into this long-running saga, by first repeating what was originally published on this website in 2020. Back in late July 2017, Dilys and I swept an adult Assassin Bug (Coranus sp) from an area of Budby South Forest. The habitat was grazed lowland heath, containing a mix of Birch and Pine scrub, areas of Bracken and Heather of various ages and condition. We took a number of photographs of the specimen at the time, thinking we were sure of it's identity. Previously, only Coranus subapterus (De Geer, 1773) and Coranus woodroffei (Putshkov, P.V., 1982) had ever been known from the UK, but on return home and after uploading the photographs to our PC's, we noticed that the underside of our specimen was very dark. The angle of our photographs were not the best, but several photographs did show the dark underside quite conclusively and after some research on the internet, we suspected that ours could be Coranus aethiops (Foster 2013). Problem was, we thought that C. aethiops was unknown from the UK, which indeed it was until Stuart Foster re-examined a series of Coranus subapterus specimens collected from Thorne and Hatfield Moors (VC63) in 1979 and 1990. Stuart found that all the specimens were actually Coranus aethiops, making it new to the UK.
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This boreo-alpine Assassin Bug is a more cold tolerant species and must be regarded as a post-glacial relict species in Britain that has long been overlooked. It can be distinguished from both C. subapterus and C. woodroffei by its black or almost completely black abdominal venter, as well as differences in the shape of the male parameres. We posted images of our specimen on a Facebook group and comments suggested that underside colouration wasn’t a reliable feature. Someone also doubted that C. aethiops would even be on Budby, as it was not suitable habitat. But then in early 2019, we were contacted by Keith Alexander, who had heard about our finding of a 'black-bellied' Coranus on Budby and had seen the photographs we had published. Keith told us that two possible C. aethiops had been found on Budby by Keith Fowler (presumably sometime in 2018) and asked if we had taken a voucher specimen. By now we wish we had, but our specimen was female and the extreme difficulty of their identification meant that a female specimen would probably have been of little use anyway. A male was needed.
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		Keith also stated in his email, that "a key identification feature is indeed the colour of the underside of the abdomen and this was not visible in our published images. Keith Fowler's Budby specimen also had a black underside and so must be C. aethiops. I have a specimen from a site in Cornwall which also has a black underside. But our specimens are all females and we need to examine a male to be 100% sure of its identity. There appear to be two black-bellied Coranus recognised in Europe at present, with C. niger being full-winged and C. aethiops short-winged, but wingedness tends to vary somewhat in some species, so perhaps should not be relied upon. The black belly does seem to be more reliable". It should be noted that back in July 2012, Dilys and myself found a Coranus sp nymph in a small area of heathland within the neighbouring Sherwood Forest CP. It's identity remained unknown and at the time was presumed to be Coranus subapterus, commonly known as the Heath Assassin Bug and what we thought was the most likely Coranus to be found at Sherwood. So the search for a male specimen continues. Anyone sweep-netting on Budby South Forest should be alert to the possibility of Coranus aethiops being present and any male specimens should be retained, so the identity of the Budby Coranus can finally be sorted out.
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This brings us nicely to the present (September 2021) and to the latest developments and eventual conclusion of this story. After Dilys and myself conducted occasional surveys to secure a male specimen, or indeed just to find another specimen at all over the intervening nine years, a concerted effort was made in August 2021 to have yet another go. I visited Budby on August 28th, which was to be the first of four attempts over consecutive dates. A variety of methods were utilised to try and find this elusive species and day one consisted of mostly beating scrub and Heather in the ungrazed roadside strip and the eastern side of Budby South Forest in general. I did try the site of the 2012 female, but after a number of fruitless hours, had nothing to show for the effort.

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Day two saw more beating of scrub and Heather in the eastern part of Budby South Forest, plus lifting up and grubbing underneath stands of Heather which allowed being lifted easily. Low branches of Pines were also sampled with the beating tray, but there remained no sign of Coranus and silly doubts that it was even there started to creep in by the end of the visit. So on day three (August 30th) I decided to concentrate on grubbing around (hand searching on hands and knees) in any pockets of leaf litter and under Heather and grasses towards the centre of Budby South Forest. This again drew a complete blank and so perhaps it was time for a rethink of strategy. August 31st and day four of the search. If you have ever lost anything, then the first place to look is usually where you last saw it, so I thought it best to return to the location of the 2012 female and try searching there again. I'd already done some grubbing in Pine litter there, but thought I'd ttry slightly further in from the path. There was some small patches of Heather growing in slightly shorter grass and it was here that a large bug moved as I shuffled a small amount of leaf litter just against the Heather. I'd found it after a near ten year wait and it was a male as well. Once potted, the black underside was easily seen and it took ages before it settled and allowed a few photographs.
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Once safely home, I contacted Keith Alexander to tell him the news and the specimen was sent to him for examination. Keith keyed the specimen out and it did indeed key out to C. aethiops, but because of the difficulty with Coranus identification, Keith sent the specimen to someone with more experience for a final decision as to its identity and Stuart Foster was able to confirm that it was indeed Coranus aethiops. It's an important record nationally, meaning Sherwood Forest becomes only the second confirmed UK site for the species and somewhat changing the criteria of C. aethiops being confined to boreal relic sites like Thorne Moors. So in the end and almost a decade later, this identification mystery has finally been sorted. It took a while, but it was worth it in the end.

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