Bush crickets make the most of autumn sun

I try to make the most of any late-autumn warmth by getting out into the field, treating each warm and sunny day as if it might be the last one before the onset of winter. While a bright morning might start with a nip in the air, it often warms as the sun rises and the small numbers of summer insects that remain can be seen on the wing or crawling across the surface of some fading leaf. The warmth of last weekend drew me to the coast and to some of the small lanes that drop down towards the beach at places like Kelling and Weybourne.

One particular stretch of low hedgerow, dense with bramble and in full sun, was alive with the sounds of calling bush-crickets. It is late in the season for these insects and many of the Breckland populations have fallen silent over recent weeks, possibly due to the handful of night frosts that we have already experienced. Here on the coast, however, there were good numbers of Dark Bush-crickets repeating their short chirping song at irregular intervals. The song is high-pitched and while I can still hear it, my birdwatching companion no longer can. With patience I was able to locate a couple of the calling individuals and point them out. Each robust and dark individual, about two centimetres in length, was calling from just within the bramble cover, producing its call by rubbing its modified wings together.

Typically, in male bush-crickets, the base of each wing is modified, with a tooth-bearing rib present on the underside of the left forewing. This is rubbed against the edge of the right forewing, next to which is a modified area, known as the ‘mirror’, which amplifies the sound that is produced. Only the Oak Bush-cricket lacks this adaptation; the male instead tapping out his drumming call with a hindleg onto whatever he happens to be standing on.

Dark-bush Crickets are robust creatures and have a long season, lasting through until the first frosts of late October or November. However, other bush-crickets are more strongly influenced by temperature and so I was a little surprised to see and hear two calling Roesel’s Bush-crickets in the same stretch of hedgerow. Roesel’s Bush-cricket is a species that has expanded its range northwards over recent years, a result of global climate change. First recorded in Norfolk in 1997, its colonisation of the county has been extremely rapid. Hot summers can boost numbers and while the 2008 summer may not have been the best, the species has clearly been fairly successful. Let’s hope they continue to call for a few more warm and sunny mornings.