General comments:
Widespread and usually common resident.

The Black Arches has not always been widespread in Hertfordshire, but during 1997 and 1998 it started to expand its range. It is now relatively widespread, but more or less confined to mature woodlands, where Hornbeam, rather than the expected oak, seems to be the principal larval foodplant. Other than the fully melanic form, which ias frequent in the Broxbourne Woods complex, adults vary considerably in the extent of their black markings and these varieties can be found in most places in the two counties.

Recorded in 37 (90%) of 41 10k Squares.
First Recorded in 1893.
Last Recorded in 2023.