Acoustic Signals in the Homoptera: Behavior, Taxonomy, and Evolution

The use of acoustic signals in communication, both within and between species, occurs widely in the Insecta (2, 35, 36). The loud airborne sounds of many groups of Orthoptera and of the large cicadas among the Homoptera are well known (1). In these groups, where communication may take place be­ tween individuals at distances very much greater than their own body length, tympanal acoustic receptors are well developed (50, 66). Some small insects are known to produce low intensity sounds. Many more possess structures that appear to be sound-producing mechanisms, but which have never been properly investigated (26, 35, 36). In recent years consider­ able advances have been made in our knowledge and understanding of the use of sound signals by small insects. For example, in species of Drosophila, and probably also in many other small winged insects, very close range, pulsed signals between individuals of the same species are produced by low frequency wing vibrations. These may only be detected by other individuals, when in very close proximity to the signaller, by the use of a displacement receptor-in Drosophila the lightly balanced antennal arista (7). In order to communicate over longer distances small insects, because of the purely physical limitations of their size, would have to use very high frequency, or ultrasonic, sounds (49, 50). However, high frequency sounds are not suitable for communication in structurally complicated habitats dominated by plants (50). An alternative that has received much attention recently is the use