Yesterday, while strolling along the route of the disused railway line that runs behind my house, it was noticeable that autumn colour seems suddenly upon us. As chlorophyll production within a leaf slows, it is the carotenes and anthocyanins that shine through and give the vivid display of yellows, reds and pinks that I love to see each autumn. No doubt the cold snap on the 13th September, where some rural location saw their first frost of the year, helped kick-start this process.

It is amazing to see how some of our insects have evolved to hide among this autumn display. Open the moth trap and some mornings it gives the appearance of being full of wind-blown leaves. Classic autumnal moths such as the barred sallow and pink-barred sallow (pictured) flare like a firebox at full tilt and are always worthy of a photo. In sharp contrast, the autumnal rustic is the lump of coal darker than the night sky.

It is the horse chestnut tree that seems to lose its healthy green look first as the leaves turn sleeper brown. This was not always the case, and it is not the autumn that brings the change. The micro moth Cameraria ohridella, horse-chestnut leaf-miner, was first recorded in the UK at Wimbledon in London in 2002. The assumption is that the moth was accidentally transported here by road or rail. From there it was full steam ahead as our transport networks aided dispersal with the moth being first recorded in Yorkshire in 2007. The moth now being abundant and widespread where the foodplant occurs.

The larvae of the horse-chestnut leaf-miner develop and feed within the horse chestnut leaf creating a blotch mine upon the upper leaf surface. A strategy that, among many benefits, helps avoid predation. Each blotch browns to give the tree that autumnal look. Horse-chestnut leaf-miners give rise to at least three generations per year with multiple young per leaf. Looking up at a tree that is now entirely brown it is hard to contemplate how many mouths it must have taken to tunnel through this much foliage over the course of a year. Under a lens the adult moth is striped like a Bengal tiger.

With the autumn equinox now passed, other trees are now stationed to join the horse chestnut. Are we on track for one of those classic seemingly endless autumnal glories we all long for? With dry ground, cool weather, and blues skies reportedly the best conditions, it is looking like we could do with a change to our current weather patterns for the best vibrant display.

wharfedale-nats.org.uk