Roesel's bush-cricket
| Roesel's bush-cricket | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Orthoptera |
| Family: | Tettigoniidae |
| Genus: | Metrioptera |
| Species: | M. roeselii |
| Binomial name | |
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Metrioptera roeselii (Hagenbach, 1822) |
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Roesel's bush-cricket (Metrioptera roeselii) is a European bush-cricket, named after August Johann Rösel von Rosenhof, a German entomologist.
Adult Roesel’s bush-crickets are medium-sized Tettigoniid between 13–26 mm in length. They are normally brown or yellow, often with a greenish shade and a rarer green form also sometimes occurs. An identifying feature is the yellow-green spots along the abdomen, just behind the pronotum, along with a matching margin along the border of the pronotum. This margin is entire, unlike its congener the bog bush-cricket.
Males and females can be easily differentiated, as the females have a long sword-like ovipositor at the end of their abdomen, which the males lack.
Both male and female adults are normally brachypterous. However, a macropterous form, f. diluta (described by Charpentier 1825) also exists. These have much longer wings, and usually make up less than 1% of the total population, but in some populations occur in much higher numbers, usually in areas where the bush-cricket’s range has recently expanded to.
They are more common in long, warm summers where populations reach higher densities. It has also been suggested that a very localised hostile environment may also produce a higher level of macropterous forms. The macropterous form is a dispersal phase, and it provides the advantage of reaching new, more favourable habitats, within which there is a lower density of Roesel’s bush-crickets residing. Well established populations tend to be more highly brachypterous, as high dispersal ability is correlated with lower fecundity in Orthoptera.
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.
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Wikipedia