Roesel's bush-cricket, Roeseliana roeselii (synonym Metrioptera roeselii) is a European bush-cricket, named after August Johann Rösel von Rosenhof, a German entomologist.
Roesel's bush-cricket is commonly found throughout southern and central Europe, as well as further North, in Finland, Latvia and Sweden. Its native range stretches from west Europe to western Siberia.
Despite being native to Europe, Roesel's bush-cricket has made its way into North America. It was first reported in Montreal and Ville St. Laurent by Urqhart and Baudry (1953) in Canada. Since then its range has increased in Ontario and Quebec, and into the United States as far as Illinois. It has been forecasted that Roesel's bush-cricket will disperse even further across eastern Canada and the United States, more likely limited to areas where grasslands are left relatively untouched across the year so as to allow the eggs to hatch.
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 (usually grasses) 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 (JH) 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.
Male adults start to sing (or stridulate) in July to attract females of the same species. Stridulation occurs for a long time (with only very brief pauses), whilst the weather is hot and sunny. The song is characteristic of the species which allows for easy identification by experts. The song consists of continuous penetrating buzzing, at a high pitch. The sound is similar to that of Savi's warbler, or the hiss of overhead electricity wires.
During the day, the male bush cricket moves to locations within the flora that lie in the sun, in an attempt to achieve the peak temperature for stridulation.
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.
