The Acoustic Behaviour of the Bush Cricket Pholidoptera Griseoaptera

1. Artificial signals have an inhibitory effect on chirping which affects whole chirps. With signals 1 sec. or less in length, the insects hardly ever chirp during the signal. If the signal is longer, chirps ’break through‘, but the chirp rate is usually less during the signals than in the periods of silence between the signals.

2. With signals of 0.1 sec. or less, the insect does not chirp until 0.4-1.0 sec. after the end of the signal. With longer signals this interval is reduced until the insect chirps during the signal.

3. Artificial signals may have an excitatory effect in increasing the total chirp rate in the period during which signals are being produced, and this effect may last for several minutes after the signals have ended. This may be due to rebound from inhibition or to a parallel excitatory effect of the signal. The excitatory effect is increased if the length of the signal is increased from 0.1 to 1 sec.

4. The excitatory effect is not so certain as the inhibitory effect and sometimes may be reversed, giving a reduction in chirp rate.

5. With very long signals (3 min.) there may be (a) a decrease in chirp rate during the signal followed by an increase after the signal, (b) a decrease in chirp rate during the signal with a very slow recovery after the signal, or (c) an increase in chirp rate during the signal followed by a decrease to normal after the signal. These effects can be more easily explained by parallel excitatory and inhibitory effects than by rebound from inhibition.

6. An increase in intensity of the signal from 40 to 70 db. gives an increase in both the inhibitory and the excitatory (or depressant) effects of the signals.

7. The rapidity and certainty of the inhibitory effect make it seem probable that few synapses are involved. The greater flexibility of the excitatory effect indicates that this effect may be mediated by higher centres in the C.N.S.

8. Recognition of the characteristic chirp of the species does not appear to be particularly important in the acoustic interaction of Ph. griseoaptera males.

The Acoustic Behaviour of the Bush Cricket Pholidoptera Griseoaptera

1. Pholidoptera griseoptera males singing alone or alternating with other males produce short chirps of three or occasionally four syllables (wing movements) lasting about 100 msec. (at 18° C.).

2. Close proximity of singing males may result in rivalry behaviour where chirps lasting up to about 4 sec. may be produced. The long chirp is not usually continuous but has a number of breaks or ‘stutters’.

3. The syllables and syllable rates in the long chirp and short chirp are essentially similar.

4. At the end of a short chirp or of a group of syllables in the long chirp, the syllable rate is decreased, possibly indicating a waning of excitation of the syllable-producing mechanism.

5. Males within hearing range of each other alternate or occasionally synchronize their short chirps. The pattern of this interaction appears to be determined mainly by mutual inhibition between the singing males. Mutual excitation may cause an in crease in chirp rate during the interaction.

6. Chirping may be controlled by a pacemaker system which can be inhibited or excited by its various inputs. A long chirp is possibly the result of a high level of excitation of this mechanism.

7. Alternation singing and rivalry behaviour between males may have a territorial significance.

Occiptalization of atlas with hypoplastic odontoid process: a cineradiographic study

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