Invertebrates
Mole Cricket
Gryllotalpidae · also called mole-cricket
A mole cricket is a cricket that has become a digging machine. Its front legs are shaped almost exactly like a mole’s, it spends its life in tunnels, and the male has turned one of those tunnels into a loudspeaker, singing from a horn-shaped burrow that broadcasts his churring call across a whole field.
Overview
Mole crickets are the family Gryllotalpidae, burrowing crickets found on every continent except Antarctica. They are cylindrical, velvety, brown, and 3 to 5 cm long, with broad, blade-edged front legs for shearing through soil. They spend nearly all their time underground, surfacing mainly at night or after rain, and many can also fly. Depending on the species they feed on roots and seeds, on soil grubs and worms, or on both.
The singing burrow
The calling male digs a burrow with a smooth, trumpet-shaped opening, sits at the narrow point, and stridulates like any cricket. The flared tunnel works as an acoustic horn, boosting the sound so it carries hundreds of metres, and a field of males produces a loud, steady churring drone often mistaken for a nightjar or an electrical hum.
Pest and rarity
The tawny and southern mole crickets, brought from South America, are among the worst pests of lawns and pasture in the south-eastern United States. Meanwhile the mole cricket native to Britain is now Critically Endangered nationally, having lost the wet meadows and marshy ground it needs.
Status
Mole crickets as a family are Not Evaluated. Some species are abundant and managed as pests; others, including Britain’s native Gryllotalpa gryllotalpa, have declined to the edge of extinction with the loss of damp grassland.
Mole Cricket: common questions
What is making a loud droning churr in the field at night?
If it is a steady, mechanical, continuous drone coming from ground level on a warm evening, especially in the south-eastern United States, southern Europe, or the tropics, it is very likely a chorus of male mole crickets. Each male sits at the throat of a horn-shaped burrow he has dug, rubs his forewings together to stridulate like other crickets, and lets the flared tunnel amplify and beam the sound outward. Individually the call carries several hundred metres; collectively a field of them produces a loud purring hum. People commonly mistake it for a nightjar, a toad or frog chorus, a distant machine, or a fault in overhead power lines.
How is a mole cricket related to a mole and to a cricket?
It is a true cricket, in the order Orthoptera along with the grasshoppers and katydids, and its own family, the Gryllotalpidae, whose name means mole cricket. It has the long antennae, wing-on-wing song, and general body plan of a cricket. It has nothing to do with the mammal called a mole beyond a striking case of convergent evolution, in which an unrelated animal that also lives by digging through soil has independently evolved short, broad, blade-edged front limbs of almost the same shape, for the same reason, to move earth efficiently.
Are mole crickets harmful to lawns and gardens?
Some species are, in some places. Where the plant-feeding, tunnelling South American mole crickets have been introduced to the south-eastern United States, they are among the most damaging pests of turfgrass, pasture, and vegetable seedlings, both by chewing roots and by loosening and drying the soil with their burrows so that grass dies in irregular streaks. Elsewhere many mole crickets are harmless or even beneficial soil predators, and the mole cricket native to Britain and much of Europe is a declining species of conservation concern rather than a pest. So whether a mole cricket is a problem depends entirely on which species it is and where.
Why has the British mole cricket become so rare?
The mole cricket was once widespread in southern England, well enough known to appear in folklore and old gardening books as the fen cricket or churr worm, but it declined steeply through the twentieth century and is now on the edge of extinction in Britain, hanging on at a handful of sites. The main cause is the loss of its habitat, the damp, undisturbed grassland, marsh edges, water meadows, and riverbank soils it needs, most of which have been drained, built on, or converted to intensive farming. Its underground life and quiet modern population also make it very hard to survey, so some records now come from people reporting the distinctive night-time churr.