Musical crickets

August is a good month in which to look for crickets and grasshoppers. After hatching earlier in the year, many species will by now have passed through a succession of nymphal instars to reach adulthood. From the rank grass outside the entrance to work, the drawn-out, high-pitched songs of male roesel’s bush crickets mix with shorter bursts from field grasshoppers. These bursts of noise are invariably the result of stridulation – the rubbing of one body part against another to make a sound. In the case of the bush crickets, modified forewings are used to produce the sound, which is then amplified by a further modification of the wing. In grasshoppers, the sound is produced by modifications to the hind legs – namely a series of stridulating pegs – which are rubbed against the most prominent veins of the flexed forewings. Some observers refer to the songs as ‘chirps’ but this can be somewhat misleading. Strictly speaking, each song is comprised of a number of syllables, with each syllable representing one complete upstroke and one complete downstroke (think of a violinist). A series of these syllables may be strung together and are then referred to as an ‘echeme’. Hence, a field grasshopper will produce an echeme of 9 syllables length, lasting some 0.2 of a second. Interestingly, the oak bush cricket lacks the wing modifications seen in its relatives and so does not stridulate. Instead it produces a drumming sound by tapping its hind legs against whatever it happens to be perched upon.

The oak bush cricket is rather unusual in two other respects; it is the only British cricket to be almost entirely carnivorous, feeding on a wide range of other insect species, and it is our only completely arboreal species. Oak bush crickets are sometimes attracted to light and the species may be found indoors or even appear in moth traps. This may explain why this small bush cricket is so often encountered across the southern section of Britain.

Another cricket that has been much in evidence in recent days is the speckled bush cricket. This is a larger beast, reaching up to nearly two centimetres in length, which can be found in its adult form from August through into November. A large female, with her beautiful, scimitar shaped ovipositor, was on our grape vine the other day; a pale green colour – with tiny dark spots – she was difficult to pick out on the leaves, reinforcing her unobtrusive nature. Despite her larger size, she is largely vegetarian in habits; a trait which could have explained the damage to the vine that had appeared within the last week. Still, I would happily tolerate this, knowing that such a fine insect was in residence.