Stridulation in four species of Messor ants (Hymenoptera, Formicidae)

This research represents the first description of stridulations produced by the different castes (gynes, males, workers) of the harvesting ants Messor minor and M. wasmanni. Further information on the stridulatory sounds produced by M. capitatus and M. structor are also given. The sounds produced by the examined samples (n = 103) of the genus Messor are homogenous in their acoustic structure and consist of long sequences of pulse-trains organized in two subunits. They are characterized by pulses with opposite phase produced by rapidly raising and lowering the gaster, so as to cause a series of ridges to rub against a scraper. For all samples of the tested species, the maximum frequency values lie within the ultrasonic range (> 18-20 kHz) and vary between 41 and 98 kHz. This is the first recording of ultrasounds produced by ants of the genus Messor Hence, the range of frequencies involved in sound production by these species is considerably wider than previously known. Moreover, the description and comparison of several acoustical parameters show some caste-dependent differences and similarities among the examined samples. The possible functional role of stridulations emitted by the different castes of these species is also discussed.