Insect hearing in the field

Summary1.Hemisaga denticulata andMygalopsis marki are two sympatrically occurring species of bushcricket. Both also have almost complete overlap in their song frequencies (Fig. 2). However, the temporal pattern of their respective songs differs considerably, males ofM. marki sing continuously compared with short bursts of song produced by males ofH. denticulata. A comparative study between two populations ofH. denticulata showed that in the presence of singing males ofM. marki, the song ofH. denticulata was suppressed (Fig. 5, Table 1). Furthermore, song interference was also demonstrated neurophysiologically in the field using the response of the omega-neuron as a ‘biological microphone’ (Fig. 4).2.In aggregations ofH. denticulata males alternate their chirp pattern, and this behaviour was used as an assay in the laboratory to test the susceptibility of intraspecific communication to biological noise. It was concluded that the precise alternating pattern between two males is significantly affected by noise (Fig. 6).3.Neurophysiological experiments performed in the laboratory revealed a strong masking effect by biological noise on the perception of the conspecific signal within the afferent auditory pathway (Figs. 7, 8). This experiment when conducted in the field exhibited similar masked responses in the omega-neuron (Figs. 9, 10).