Macropterous

It was a heavy, thundery kind of day that conspicuously failed to deliver the rain we needed, but did provide horrible air quality and very poor light. (I blame Remoaners. I mean - why not? We seem to be responsible for everything else.) R and I went to Stratford at lunch time, so that he could get some steps in and I could do some shopping and - I hoped - take some photos. Coffee and cake may also have featured.

This is a female Roesel's bush cricket, who foolishly drew attention to herself while I was fruitlessly searching the bank of the river for Odonata. On the other hand, I foolishly lowered the camera to move the grass stalk that cuts her foreleg in this image, so as to improve my next shot, only to see her take advantage of my 'eye' being off her and spring away to freedom. So I guess we're quits.

Roesel's bush crickets were originally a coastal species in the UK, but they can utilise any rough, ungrazed grassland, including railway embankments and road verges, and over recent decades they've spread widely across south-east England and the Midlands. This colouring is typical, though I have found specimens that were much greener than this, but the pale edge to the pronotum is diagnostic. This is an omnivorous cricket, eating mainly grass seeds, but also smaller insects. Adults can be found from late June through to September or October. Females lay their eggs inside grass stalks, which they cut open with this scythe-like ovipositor, and the nymphs emerge the following April and May, passing through six instars to reach adulthood.

The most interesting thing about this female is the fact that she has long, fully functional wings, whereas the wings of most Roesel's bush crickets are rudimentary. The 'normal' form, which is described as brachyopterous, has to move around by walking or springing, but this macropterous form - called Metrioptera roeselii, f. diluta - is able to fly, and can thus travel far more widely, and disperse what might otherwise be a relatively static population to new areas. Generally less than 1% of Roesel's bush crickets are macropterous, but it's believed that this proportion increases in particularly warm summers, or when the population becomes too dense at a particular site. A higher proportion of macropterous individuals within a population is associated with poorer reproductive outcomes, so it's not surprising that once dispersed individuals have settled and become established at a favourable site, this new population tends to revert to being largely flightless.

The lengthy, high-pitched song of the male Roesel's bush cricket, which it produces by rubbing its wing edges together, is usually likened to electrical interference. There's a good recording of it on this page.