By James Duncan
Learning and Engagement Officer
The Dark Bush Cricket (Pholidoptera griseoaptera) belongs to a substantial Order of insects known as the Orthoptera, a grouping that comprises well over twenty thousand species worldwide. The Crickets and Grasshoppers are the two Orthopteran families most likely to be seen here in Britain, with around thirty species distributed throughout the country. It would seem quite easy to confuse the two, but they're actually quite different in both their anatomy and behaviour. Should you spot one with thread-like antennae longer than the body, chances are it's a cricket; if they're shorter and stubbier, it's a Grasshopper. The bush-crickets can be further recognised by their highly extended back legs, the enlarged femora helping them to achieve superb abilities in 'long jump' and giving them a 'leggy' look. Ironically, rather than jumping, you're far more likely to see a Dark Bush Cricket crawling and sunbathing amongst ancient hedgerows, within their favoured vegetative mix of Bramble and Nettle, particularly in the southern half of Britain where they're the most common. Crickets are also rather more voracious, their omnivorous diet comprising a host of smaller insects; grasshoppers are largely vegetarian.
As opposed to the sun-loving grasshoppers, the bush-crickets are somewhat more crepuscular, active mainly in the latter part of the day. In fact, orthopteran activity is quite possibly the very essence of summer, the buzzing and chirping dominating many a grassland habitat. Bush-crickets generate their song through stridulation of their wings alone, differing from grasshoppers who rub the hind legs against the wings. The song generated by Bush-crickets tends to be higher pitched and it's only the males that are capable of doing it - they have very short vestigial forewings, whereas the females have nothing but small lobes remaining. The 'left handed' Dark Bush Cricket stridulates by rubbing file-like 'teeth' on the left wing across a hardened 'scraper' on the right - imagine fingernails across a comb. The male may produce either a staccato chirp to attract a female or an extended growl to challenge a rival male. Interestingly, a heterodyne bat detector may be tuned to 22kHz to listen in to their vocalisations. Both sexes have 'ears' for perceiving sound, though they're not quite where you might expect - the drum-like membrane for detecting vibrations, known as a tympanal organ, is in fact located on the mid-section (tibia) of the front leg.
Now's a great time to look for the Dark Bush Cricket, though you may not find the adults quite yet, for they grow in stages known as nymphs, a process of partial metamorphosis. As a cricket develops from egg to adult it'll shed its skin six times, each miniature version gaining size and appearing successively more like the robust, armour-plated adult. The adult female will even appear to wield a mighty sword, protruding from her abdomen, though it's actually an ovipositor, used for either laying eggs in soil or cutting slits in vegetation for receiving the eggs. These will be laid in late summer, though amazingly the nymphs won't emerge until spring two years later. They usually mature from July, when the males will launch into their song. Unfortunately the sound generated by Orthoptera is not what it once was, diminishing in a rural landscape with vastly reduced meadows and a significantly greater proportion of intensively managed farms.
Dark Bush Cricket - nymph © James Duncan