Neurobiology and biomechanics of flight in miniature insects
authors: Sanjay P Sane
doi: 10.1016/j.conb.2016.09.008
CITATION
Sane, S. P. (2016). Neurobiology and biomechanics of flight in miniature insects. Current Opinion in Neurobiology, 41, 158–166. https://doi.org/10.1016/j.conb.2016.09.008
ABSTRACT
fleeting notes
model organisms for studying insect flight
- there are even tinier insects like phorid and scatopsid flies. there are tinkerbella wasps for example under 1mm in size.
- Reynolds numbers - the ratio of inertial to viscous forces on wings
- miniature insects with low Re need to continuously flap wings or they will stop moving
- increasing wingbeat amplitude and frequency increases Re
- most small insects optimize their amplitude rather frequency based on the constraint of the “clap and fling” method of flying - both wings clap at the end of the upstroke
- but larger insects like drosophila do not do this
- to ease energy expenditure during flight, mini insects have independently evolved ptiloptery-long cilia on wing margins
- they can act like paddles to help generate more flight forces with less inertial load
- thrips have individual setae that are locked in one of two configurations
- they can change the configuration by combing before or after flight
the thorax mechanically links wings and halteres through oscillations
- mechanically linked thoracic framework that coordinates wings and halteres in flies
- originally identified in soldier flies but probably present in all insects that possess indirect asynchronous flight muscles
- mechanically linked thorax helps wing coordination at faster rates than what nervous system can control
- brain just needs to make sure power muscles driving thoracic oscillations are periodically active
- however this constrains wings from moving independently
flying insects decouple wings from thorax for steering
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smaller insects with miniaturized neurons results in more intrinsic noise and noisier feedback
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smaller insects have worse vision
- fewer ommatidia
- smaller lens diameter means greater diffraction and worse spherical chromatic aberrations and more image blur
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there is very little room for size reduction in molecular machinery for eyes and for olfaction
- sense of smell in mini insects is limited to close range and limited set of odors
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johnstons organs in mini insects are not well studied
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in diptera, hind wings evolved into mechanosensory halteres which give feedback about angular velocity
- during flight, halteres oscillate in phase with wings
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flight muscles are usually separated into direct or indirect flight muscles
- in some insects a single nerual pulse can result in 10 wing beats because the thoracic shell creates a resonant chamber
- delayed stretch activation - property of power muscles where force is generated once they are extended
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phase relationship between muscles and motor neuron activity is decoupled in asynchronous flight muscles