Olive Crescent - coming to a moth trap near you

Not so long ago, the Olive Crescent was confined to the Stour Woods RSPB reserve in Essex. I did a bit of work on its ecology there, with much assistance from the RSPB staff and volunteers. The larvae feed on dead leaves of oak and Sweet Chestnut there and we found that they had a preference for Sweet Chestnut leaves that were in full shade.

Occasional individuals at south coast locations show that Olive Crescents do occasionally migrate from the continent and in the early 2000's it seems that such migrants managed to establish one or more colonies in the far east of East Sussex. Over the next few years they seemed to consolidate their foothold but there wasn't much evidence of significant range expansion. Last year one adult was caught near Tunbridge Wells which was as far west as it had been seen in suitable breeding habitat. So this year the RSPB at Broadwater Warren and Sussex Wildlife Trust at the adjacent Eridge Rocks cut some oak branches and hung them up in the hope that larvae could be found later in the year. I joined them for the search and we found larvae quite easily at both sites.

Flushed with success I decided to have a look for larvae in Hampshire near Petersfield where several adults had been seen earlier this year. At this site they were likely to be feeding on Beech leaves (as they do at Friston Forest and some other sites in East Sussex) and luckily there had been some thinning of the Beech at this site earlier in the year, leaving stacks of suitable branches. I quickly found several larvae which were exceptionally variable in colour.

This was the first confirmed breeding in Hampshire but there was still no record of breeding in West Sussex so I headed over to the downs above Graffham where an adult had also been caught earlier this year. I didn't have the luck of having pre-prepared branches like at Broadwater Warren or forestry thinnings like at Petersfield and it took a long time to find any suitable branches but when I finally found a snapped off beech limb I instantly found three larvae.

During the hunt for the branches I came across a new plant species for me in a game strip; Small Nettle.

So what about the gap between Tunbridge Wells and Graffham? There are very few moth recorders in central Sussex away from the coastal towns and I suspect that the moth has been quietly spreading west without anyone noticing.

Olive Crescents are also spreading in Essex and the first larvae were found in Suffolk this year so if you live in south-east England, look out for this species in your trap soon.