Phonotaxis inGryllus campestris L. (Orthoptera, Gryllidae)

Summary

Acoustic orientation of receptive female crickets (Gryllus campestris L.) towards the calling song (Fig. 2) of a conspecific male is investigated using a locomotion compensator (Fig. 1). By applying this method we restrict neither the path-length nor the walking direction of the walking cricket. At the same time the method provides a continuous record of the walking parameters (path of the cricket, velocity, walking direction, and angular velocity).

The locomotion compensator ensures that the distance between cricket and loudspeaker and thus the calling song intensity remain constant; nevertheless the phonotactic response is not seriously affected during the experiments (Fig. 6).

Compared to walking without calling song presentation (Fig. 3), acoustically orientated walking shows the following characteristic features:

• (i) persistent course towards the sound source (Figs. 6–8);

• (ii) oscillations of 30–60 ° amplitude around the direction of the sound source (Figs. 8, 10);

• (iii) a nearly sinusoidal angular characteristic of corrective turns (Fig. 9);

• (iv) increased mean velocity (Fig. 4);

• (v) short stops (about 0.6 s) with small variance in duration between continuous walking periods of variable duration (Fig. 10, Table 1).

Gryllus campestris females utilize information about sound direction both during stops and during walking (Fig. 10). However, the time needed for correction of a given course deviation during walking exceeds that during stops (Fig. 12).

With increasing calling song intensity the crickets pursue their course direction more precisely and the correspondence between mean walking direction and sound direction improves (Figs. 13–15).

The female crickets investigated exploit bilateral differences in reaction amplitude of auditory neurons and not those in reaction time for detection of sound direction (see Discussion).