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

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/632/movelectures/sound/insect.htm

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

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

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

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

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

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

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

Overcoming physical obstacles Resonance Baffle Horn Sound production Sound reception

Resonance Mass and a spring; resonant frequency 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 terrtorial

oscillogram Gryllus EMGs sound sonogram

wing plectrum

add wax to harp frequency reduced resonator affected

remove teeth

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

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

Hearing locust = grasshopper ears

Tympanum structure

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

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 Modified wings for sound production Modifying the environment for sound production Modified cuticle to hear

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 Many insects use sound produce it quite efficiently hear it effectively