Fern Horisme tersata

Sometimes called The Fern, a abhorrent hangover from centuries past.

Recorders should be aware that Cryptic Fern Horisme radicaria is now known to occur in the UK (mainly in the SE but possibly also in Norfolk), so all ferns should be checked carefully.

This species isn't desperately uncommon in some parts of Norfolk but it's quite local and across much of the county it's very scarce indeed. This one was caught in my garden, the first here in over 11 years of more-or-less nightly trapping and the first I'd encountered anywhere. It was good to compare it with the Cryptic Fern that I had caught in Kent earlier in the same month. Certain identification of Cryptic Fern, at least in areas where it is not clearly established (including Norfolk currently), should be confirmed by examining the genitalia.

male Fern Horisme tersata showing genitalia including right saccular projection, North Elmham (Norfolk, UK), 28th May 2026