Autumnal Mothing

As we move into September the moth trapping season is beginning to wind down. The number of moths and diversity of species begin to decrease with each recording session. Lower night time temperatures and increasing likelihood of rain also mean there are fewer opportunities to run the trap. A warm, dry night at this time however, can signal the chance of an interesting catch, with the potential for a small range of distinctive autumnal species as well as the prospect of a rare migrant.

One particular species tends to dominate my trap in autumn – the Large Yellow Underwing. Late August to early September is the peak of the flight season for this fairly big moth, and at this time it is not uncommon for over 100 individuals to be filling the trap in a single night's catch. In some locations on the south coast several thousand may be caught in just one trap, as local moths are joined by migrants from the near continent. Accompanying the Large Yellow Underwings are other routine species, which are also found in fair numbers. These include Lesser Broad-bordered Yellow Underwing, Vine’s Rustic, Square-spot Rustic (which comes in an incredible variety of forms) and the curiously named Setaceous Hebrew Character.  

A plague of Large Yellow Underwings

Autumn is the time of the year when one of my favourite groups of moth start appearing – the Sallows. These striking moths are generally woodland species, which have evolved a yellow, orange and brown colour mix to their forewings in order to camouflage against the autumnal senescing leaves. In recent years I have had a good record of attracting species from this group into my suburban garden. The most commonly found is Barred Sallow, which is the only member of the group that appears in fair numbers. Sallow and Dusky-lemon Sallow are less frequent and this year I have recorded my first Orange Sallow - a stunner! The remaining common members of the Sallow group - the Pink-barred and Centre-barred Sallow have eluded me thus far but I am hopeful to catch one in the coming weeks. Pale-lemon Sallow is a much scarcer member of the group, though has been noted fairly frequently in Cambridgeshire. 

Sallows: (Clockwise from top left) Barred Sallow, Sallow, Orange Sallow and Dusky-lemon Sallow

Micro moths are much less numerous in autumn compared with the summer months, with only a handful of species recorded in most trapping sessions. There is however always the potential for a few interesting species turning up and trapping on a warm night this week provided me with four new micros for the garden list. Box-tree Moth was one of these new species. I was previously familiar with these invaders after seeing numerous reports from the London area, though few have so far reached Cambridgeshire much to the relief of local gardeners. On finding this invasive species in the trap I was amazed to see how big it was; far larger than most micros and even some macro species! In all likelihood Box-tree Moths will become a regular sight in the garden in the near future, but hopefully not to the extent which has occurred in France earlier this year. 

Another highly distinctive micro species caught this week was Epiblema foenella; a fairly large tortricidae species with conspicuous white-angle marks on the wings. Agonopterix nervosa was also new and to my surprise a fairly scarce species locally.  

Box-tree Moth

Epiblema foenella

Agonopterix nervosa