The Elaborate Courtship Behavior of Stenobothrus clavatus Willemse, 1979 (Acrididae: Gomphocerinae)

The elaborate courtship behavior of the gomphocerine grasshopper Stenobothrus clavatus, endemic to a few mountains in Greece, incorporates acoustic signalling and visual display elements to prime the conspecific female. The courtship song, produced by rubbing hind legs against an elytral vein, can be divided into four consecutive phases. The basic movements of phases I, II and IV consist of simple up and interrupted downstrokes, with sound produced during the downstroke only. In contrast, phase III is characterized by a fast sound-producing elevation of the femora, a kick of the tibiae and other visual display elements, such as a fast raising of the antennae with their dark spatulate tips during each movement cycle. The latter is strongly pronounced and therefore a characteristic feature of this species.

The stridulatory file of each hind leg consists of two parts. The proximal part bears a double row of little pegs, whereas the pegs in the distal part are regularly aligned in a single row. The proximal part of the stridulatory file is incorporated in sound production only during phase III. However, frequency spectra from different sound elements produced during phase III were similar. Nevertheless, differences are found between phase I/II and phase III/IV, which are ascribed to variations in contact pressure of the stridulatory file against the forewing, rather than to different portions of the stridulatory file being involved.