Complex songs and cryptic ethospecies: the case of the Ducetia japonica group (Orthoptera: Tettigonioidea: Phaneropteridae: Phaneropterinae).

In many groups of animals, especially insects, genital morphology is species distinctive. This is true of bush-crickets or katydids (Tettigonioidea). The calling songs produced by males are species distinctive and do not change significantly during the early stages of speciation. Their patterns are usually relatively simple. We present an example where none of these assumptions is true. Since the last revision of the genus Ducetia in 1961, one widespread species, Ducetia japonica (Thunberg, 1815) has been thought to be morphologically uniform. It is represented by tens of specimens from south and eastern Asia and Australasia on both sides of Wallace's Line. The male genitalic appendages vary little over the extent of its range. In contrast, the calling songs differ considerably from place to place. Examination of the stridulatory organs of both sexes (located on the first set of wings) reflects the differences in song. The teeth, which produce the sound, differ in shape, number, and size. We present details of the song patterns and the stridulatory organs that produce them. As a result, some synonyms are re-established, and new species are described. Chromosomal information is presented for two species. The origins and the distribution and expansion of the group are detailed. Duets between courting pairs have played an important role in the evolution of this song structure where efforts to trick eavesdropping rivals are common. [ABSTRACT FROM AUTHOR]