1. Communication and the nervous system http://biolpc22.york.ac.uk/632/
Sound in insects
Communication and the nervous system

2. References
Young, D (1989) Nerve cells and animal behaviour CUP [1st edition, chapter 7]
Also, chapters in:
Carew Behavioral neurobiology
Zupanc Behavioral neurobiology
papers are on the web

3. Main points of lecture Sound transmission is inefficient
Insects use sound in a major way
Overcoming physical obstacles
Modifying
wings for sound production
the environment for sound production
cuticle to hear
Private communication

4. About sound
sound is a wave of particle compression and rarefaction   
energy (or power) is transferred from sender to hearer
sound gets quieter further away
sound has to be discriminated according to species, context and from random noise

5. Speed of sound
speed c determined by the Pressure P, the density  and a fudge factor  (close to 1)
for water
1430 m/s
for air
330 m/s

6. Sound properties speed c (m s-1) wavelength l (m)
frequency f (Hz, cycles/s)
for 330Hz, wavelength 1m
for 3.3kHz, wavelength 0.1m
for 33kHz, wavelength 0.01m = 10mm

7. Acoustic impedance impedance Z determined by speed c and density 
for water
1.5 * 106 kg m-2 s-1
for air
330kg m-2 s-1

8. Power transfer - i First problem for an insect -
Power transferred from one medium to another (plane wave)
for air/water interface about 0.02%

9. Power transfer - ii Usually other insect far away -
With distance, power decreases
more bad news for insects!

10. Power transfer - iii Usually insects small -
sound emitted is dependent on ratio of insect size / wavelength of sound

11. Power transfer - iv
if you are smaller than 0.2 * l more bad news!

12. Insects use sound in a major way
Mantids*
Grasshoppers/crickets*
bugs*
beetles*
diptera (true flies)*
lacewings
moths

13. Overcoming physical obstacles
Resonance
Baffle
Horn
Sound production
Sound reception

14. Resonance Mass and a spring; resonant frequency s is stiffness, m mass
below fo in phase; at fo 90o; above fo out of phase

15. Gryllus Field cricket nice loud song, carries a long way
attracts females & males
terrtorial

16. oscillogram
Gryllus
EMGs
sound
sonogram

17. wing
plectrum

18. add wax to harp
frequency reduced
resonator affected

19. remove teeth

20. Gryllus campestris
sound output 60 mW
muscle work 2 mW
efficiency 3%

21. Bush crickets
Higher frequency
damped oscillation

22. Baffle
Bush cricket
Oecanthus
power * 12

23. Gryllotalpa
mole cricket

24. Horn shaped burrow

25. Gryllotalpa
sound output 1 mW
muscle work 5 mW
efficiency 20%

26. Summary so far Modified wings for sound production
Modifying the environment for sound production

27. Hearing
locust = grasshopper ears

28. Tympanum structure

29. Tympanum structure Muller’s organ has sensory endings in it
side view
Muller’s organ has sensory endings in it
Tympanum (ear drum) taut membrane
top view

30. Movement
it’s the relative movement which will stretch the axons

31. Movement peaks at 3 & 6kHz indicate resonance
resonance also shown by phase plot
folded body not in phase with membrane
even when at 4kHz amplitude is same
relative movement needed to stretch axons of Muller’s organ

32. Cricket hearing
acoustic trachea
acts like horn for 5kHz sound

33. Summary so far Modified wings for sound production
Modifying the environment for sound production
Modified cuticle to hear

34. Drosophila courtship
Male has black tip
Olfaction
Singing

35. Detecting vibration near field sound movement detector
aristae - bristles on antennae

36. Private communication
Sound movement in dB
since sound is measured on a log scale, 80 << 95

37. Summary Many insects use sound produce it quite efficiently
hear it effectively