Leiodes cinnamomea

Apparently a scarcely-recorded species in Norfolk (the last update I saw from the county recorder had 3 records up to the end of 2021). Duff mentions that it can come to MV light though, and that's how I found mine. Apparently the species is associated with truffles under Beech.

The identification of this was not totally straightforward. Once I'd worked out that it was Leiodes I used Duff's key. The elytral stria 9 deviated away from the elytral margin towards the base which led me to a series of couplets that I found hard to judge. In the end taking all possible options they all led to species that were considerably smaller than my specimen (getting on for 6 mm). I wondered it the deviation in stria 9 wasn't significant enough to count and tried the alternative option which led straight to a choice between cinnamomea and oblonga, both of which seemed equally unlikely given the low number of Norfolk records. The shape of the pronotum and almost black antennal club pointed to cinnamomea but I felt I should check for an aedeagus to confirm genitalically if possible. Sadly it turned out to be a female so this didn't help.

I now turned to Hackston to see if this could improve my confidence. Certainly it helped clear up the issue with stria 9 with descriptions and illustrations that very clearly put mine in the cinnamomea/oblonga camp (stria 9 didn't go anywhere near stria 8). But it also introduced a slight doubt about which of the two it was as one of the features it uses to distinguish them is the width of the antennal club (very broad in cinnamomea and relatively narrow in oblonga). I felt mine was closer to the photo of oblonga in this respect, and checking some other photos of cinnamomea I didn't think the antennal club on mine was quite as broad as it was in those photos. Moreover some photos of oblonga seemed to show a darker antennal club than either Duff or Hackston suggests should be the case. In the end, after weighing up all the characters in both keys and comparing to photos of both species I feel that the balance is tipped sufficiently strongly in favour of cinnamomea. Some of my photos seemed to make the antenntal club look broader than others and it looked fine for cinnamomea in those. I'll keep hold of the specimen for now though in case anyone wants to have a look.

female Leiodes cinnamomea showing mesosternal keel, pronotum and antenna (2 photos), antennal club, base of elytral stria 9 and hind tibial crenulation, North Elmham (Norfolk, UK), 24th November 2024