Nigel Brown’s understandable joy in finding a rosy footman in his moth trap (Country diary, 25 August) ends with “an important ecological message” that the substantial elimination of airborne sulphur dioxide pollution, which was devastating to the lichens and algae on which caterpillars of footman moths largely feed, has allowed recovery and even geographical spread.
However, what might be a more realistic message is that the balance has changed in our major airborne pollutants since the 1990s, from sulphur dioxide to nitrogen oxides (a byproduct of internal combustion engines, among others), and this has benefited lichens and algae, which thrive under the current regime – and hence also footman moths as a special case.
