Neuroethology:
Sound in insects
http://biolpc22.york.ac.uk/404/
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
http://biolpc22.york.ac.uk/404/cjhe/
cricket_singing/insect.htm
What is neuroethology?
 approach to analyse neural function in terms
of evolutionary advantage
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
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
Sound properties
c  f l
 speed c (330 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
Power transfer - i
 First problem for an insect  for air/water interface about 0.02%
Power transfer - ii
 Usually other insect far away  With distance, power decreases
 more bad news for insects!
1
 2
d
Power transfer - iii
 Usually insects small  sound emitted is dependent on
ratio of insect size / wavelength
of sound
Power transfer - iv
 if you are smaller than 0.2 * l more bad news!
Insects use sound in a major
way
 Mantids*
 Grasshoppers/crickets*
 bugs*
 beetles*
 diptera (true flies)*
 lacewings
 moths
How do they manage this if
physics is so unfavourable?
Overcoming physical obstacles
 Resonance
 Baffle
 Horn
 Sound production
 Sound reception
Resonance
 Mass and a spring; resonant frequency
1
fo 
2 
s
m
 s is stiffness, m mass
 below fo in phase; at fo 90o; above fo out of
phase
Gryllus
 Field cricket
 nice loud song,
carries a long
way
 attracts females
& males
 territorial
oscillogram
Gryllus
EMGs
sound
sonogram
Females…
… walk to the loudest sound
Sound made by
wing
plectrum
add wax to harp
 frequency reduced
 resonator affected
remove teeth
Gryllus campestris
 sound output 60 mW
 muscle work 2 mW
 efficiency 3%
Can they do any better?
Bush crickets
 Higher frequency
 damped oscillation
Baffle
 Bush cricket
 Oecanthus
 power
* 12
Gryllotalpa
 mole cricket
Horn shaped burrow
Gryllotalpa
 sound output 1 mW
 muscle work 5 mW
 efficiency 20%
Summary so far
 Modified wings for sound production
 Modifying the environment for sound
production
Well done the male crickets!
Now onto: what about hearing?
Hearing
 locust = grasshopper ears
Tympanum structure
Tympanum structure
side view
 Muller’s organ
has sensory
endings in it
 Tympanum (ear
drum) taut
membrane
top view
Movement
it’s the relative movement which will stretch the axons
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
Cricket hearing
 acoustic trachea
 acts like horn for 5kHz sound
Summary so far: Resonance!!
 Modified wings for sound production
 Modifying the environment for sound
production
 Modified cuticle to hear
Now onto: shh, let’ keep this to ourselves?
Drosophila courtship
 Male has black tip
 Olfaction
 Singing
Detecting vibration
 near field sound
movement detector
 aristae - bristles on
antennae

Private communication
 Sound movement in
dB
 since sound is
measured on a log
scale, 80 << 95
Summary
 The neuroethological approach relates the
function of the nervous system to its
evolutionary advantage
 Many insects use sound
 produce it quite efficiently
 hear it effectively