Roesel's bush-cricket (Metrioptera roeseli) is a European bush-cricket, named after August Johann Rösel von Rosenhof, a German entomologist. Its song is very similar to that of Savi's Warbler. Its body length as an adult insect is 15 to 18 mm (0.6 0.7 in). It is brown with a pale margin to the sides of the pronotum (this margin is entire, unlike its congener the bog bush-cricket). Its forewings usually reach midway along its abdomen at rest. However there is a macropterous form of this insect (f. diluta), in which the wings reach beyond the tip of the abdomen. This form appears predominantly during hot summers and enables the species to extend its geographical range rapidly while conditions are suitable; such migrations may also be in response to local over-population.