Roesel's bush-cricket

Status

Roesel's bush-cricket is native to Great Britain and Ireland. It is becoming one of the most commonly found Orthoptera in the British Isles, and makes up about 16% of records. It used to be found uniquely on the inland side of saltmarshes, and in coastal regions around estuaries, on the North Sea coast. It is becoming increasingly common in southeast England, as well as spreading further north. Over the past 50 years it has ranged further to the west, and large numbers have settled in areas of urban wasteland, especially near railways. It is generally found below 100 metres altitude. Extension to the species range has increased substantially since 1985.

Habitat

Vegetation structure and species both influence bush cricket distribution. Grass length is one of the key structural factors, as shorter grasses leave the bush crickets more at risk from predation and environmental disturbance, whereas longer grasses block out light. The height of grassland is also important in song propagation, and a higher position for stridulation is essential for many bush crickets as grasslands have a hampering effect on noise. Sward height preferences change depending on the time of year.

Roesel's bush-crickets have a preference for ungrazed meadows, with tall grass swards, which are a component of its diet. Other parts of their diet are grass seeds and smaller insects. They also have a preference for humidity, and thus require grasslands which remain reasonably undisturbed.

Due to its affinity for tall grasses, they can be found in a variety of habitats, including long swards at the edges of roads, field borders and pastures.

Evolution

Roesel's bush-crickets have only one generation every year. In the summer and autumn, the sword-like ovipositor of the female adult is used to cut open plant stems and lay the egg pods within.

They emerge in May as nymphs. These must go through five or six instars before becoming adults. The final instar may be the most important in determining whether the insect develops as a brachypterous form or a macropterous form. It has been suggested that production of macropterous forms may be due to juvenile hormone degradation in the final instar, which leads to a shorter period of JH presence within the nymph. This allows more flight muscle and wing production during metamorphosis.

Adults tend to emerge in late June to early July. When the climate is mild enough, some can still be found at the end of October. Brachypterous forms disperse through the environment by walking along roadside grasses and ditches.