High ultrasonic and tremulation signals in neotropical katydids (Orthoptera: Tettigoniidae)

Abstract

Myopophyllum speciosum is a pseudophylline katydid (Tettigoniidae) from the neotropics that generates unusually high ultrasonic frequencies as the dominant carrier in its calling song. Male calls average only 148 ms duration and are given at long intervals: 8.7 s. Pairing is completed with vibrational signals, generated at closer range by body oscillation (tremulation). Two distinctive vibrational motor patterns, short and long, are produced by both sexes. Physical parameters of the sound and vibratory signals of this species are described. The relatively high‐Q carrier frequency (mean = 81 kHz) varies between males over a range of 20 kHz but does not predict a singer's body size. Short tremulations are much more intense than long as measured by acceleration. Descriptions of the songs of three other pseudophylline species with unusually high principal carriers (65–105 kHz) are also presented. Eavesdropping by predatory bats offers the most plausible selective explanation for the features of M. speciosum's signal system. This hypothesis is supported by the species' sexually dimorphic defensive spination: males, the sound‐signalling sex, have metafemoral spines of greater size and distinctive orientation. Evidence for eavesdropping and for alternative hypotheses is assessed. Other neotropical tettigoniids in rainforest understorey also employ elaborate vibratory signals (species of Choeroparnops, Schedocentrus, Docidocercus, Copiphora) and some show a trend to reduce or even to eliminate their use of airborne sound. Some rainforest tettigoniids may have replaced acoustic with vibrational signalling as a response to bat eavesdropping.

Wing mechanics, vibrational and acoustic communication in a new bush-cricket species of the genus Copiphora (Orthoptera: Tettigoniidae) from Colombia

“…Morris et al (1994) brevirostris sing with a very low duty cycle, and produce acoustic signals mostly with ultrasonic energy (Fig. 3, see also Morris et al 1994). Similar to C. (Belwood, 1988(Belwood, , 1990Belwood and Morris, 1987;Morris et al, 1994;Römer et al, 2010).…”

“…Perhaps this lower frequency aggressions signal could be associated with abrupt large body movements. Complex vibrational signals might be the result of the adoption of reduced singing behaviour as a defensive adaptation against bats (Morris et al 1994), see below. Morris et al (1994) brevirostris sing with a very low duty cycle, and produce acoustic signals mostly with ultrasonic energy (Fig.…”

“…Vibrational communication, also known as seismic tremulation, is the communication between organisms by the vibration of a substrate. In bush-crickets it is speculated that tremulation functions to attract females whilst reducing the cost of acoustic eavesdropping by predators and also allowing for an alternative communication channel (Morris, 1980;Morris et al, 1994;Römer et al, 2010). Some species seem to have dramatically reduced their acoustic behaviour and adopted tremulation as a key modality for communication with females (Belwood and Morris, 1987).…”

“…Many species of bushcrickets communicate using ultrasonic channels, with pure tone ultrasound signals prevailing in neotropical species (Montealegre-Z, 2009). Pure tone signals seem to be common in species of the genus Copiphora (Montealegre-Z and Postles, 2010;Morris, 1980;Morris et al, 1994), with most of the energy occurring in the ultrasonic range (Montealegre-Z, 2009). …”

“…Such acoustic behaviour is commonly combined with body vibrations transmitted through the substrate as an alternative channel of communication (Morris et al, 1994;Stumpner et al, 2013). Vibrational communication, also known as seismic tremulation, is the communication between organisms by the vibration of a substrate.…”