#3
Thanks. I think you're right. According to key and figures in Rozkosny 1973, Beris-larvae are recognizable by the tufts of bristle-like hairs, which are present in this larva too (I collected two specimens, which unfortunately are dried out now).
I found a few of these larvae on the underside of the mushroom Polyporus badius, on two different localities. I wondered whether this was just coincidental or whether the larvae really like this mushroom...