Data from: Position-dependent hearing in three species of bushcrickets (Tettigoniidae, Orthoptera)

A primary task of auditory systems is the localization of sound sources in
space. Sound source localization in azimuth is usually based on temporal
or intensity differences of sounds between the bilaterally arranged ears.
In mammals, localization in elevation is possible by transfer functions at
the ear, especially the pinnae. Although insects are able to locate sound
sources, little attention is given to the mechanisms of acoustic
orientation to elevated positions. Here we comparatively analyse the
peripheral hearing thresholds of three species of bushcrickets in respect
to sound source positions in space. The hearing thresholds across
frequencies depend on the location of a sound source in the
three-dimensional hearing space in front of the animal. Thresholds differ
for different azimuthal positions and for different positions in
elevation. This position-dependent frequency tuning is species specific.
Largest differences in thresholds between positions are found in Ancylecha
fenestrata. Correspondingly, A. fenestrata has a rather complex ear
morphology including cuticular folds covering the anterior tympanal
membrane. The position-dependent tuning might contribute to sound source
localization in the habitats. Acoustic orientation might be a selective
factor for the evolution of morphological structures at the bushcricket
ear and, speculatively, even for frequency fractioning in the ear.