Evan and Carolyn reported a Broom moth (Melanchra pisi) in the earlier post, a species which was common throughout the country. In Butterfly Conservation's "The State of Britain's Larger Moths 2013" the Broom moth is reported to have declined by 84% over the last 40 years. The following graph shows the number of individuals of the Broom moth recorded per year at a single Rothamsted site in the county since 1976. Following the spike in 1995-96 their numbers declined significantly, actually reaching 0 in 2013.
None of the normal suggested causes for this would seem to apply, ie habitat change, agricultural intensification, light pollution and it seems rather sudden for climate change.