Flight & locomotion
Part 3: Flying as an insect
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Minilecture:
The evolution of the wing
The evolution of the wing is a hotly debated topic. The evolution of the wing may have come from the notum (top of the insect), the pleurum (the side sclerites) or from the leg area (near the coxa).
A Hypothetical wingless ancester |
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The wing
The basic structure of the wing is generally a series of veins, which has a basic design:
The wing venation allows for structural stability, which involves alternating between wing veins and cuticle between them, resulting in an accordian-like effect, which can strengthen the wing:
Check out the website below for more information in insect wings: http://en.wikipedia.org/wiki/Insect_wing
The wing structure: diverse designs
Wings can be very different, from massive complex wings as in the stick insect (left) to single streamlined wings, such as flies (below).
In the smaller insects, such as thrips and aphids, the wings can be reduced to a few veins or are even feathered (as in thrips) or scaled (such as the mosquito below).
These insects are so small that moving through the air can be more like swimming through the air because the forces are very different .
Wing folding
Several insects, such as beetles and hemipterans fold their wings, which involve hinging the middle of the wing or folding it along specific veins or creases
Wing attachments to the thorax
Check out the website below on the anatomy of the thorax: http://www.earthlife.net/insects/anat-thorax.html
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The wing attachments to the thorax involve a complex series of sclerites embedded in membraneous cuticle. The flight musculature can attach directly to these sclerites, which can change the angle of the wing, with the front edge of the wing being deflected downward or upward |
The wing structure: How it flaps
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Throughout this path, fine vortices of air move along the wing veins, allowing the air to move faster over the top of the wing, resulting in lift.
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The wings can generally move around along a figure eight, where the wings move back, are flipped upside down, and rotates around so they are right side up, generally moving across along a ‘figure eight’ path.
The wing actually flips around, such that the vortices can be created along its surface with each flipping of the wing, as indicated in this side view of the wing. Insects can flap their wings up to and beyond 400 beats per second, though this occurs mostly in flies.Other ways that insects fly is the ‘clap and fling’, which is seen in butterflies and moths. For more information on flight, check out the following websites:
http://en.wikipedia.org/wiki/Insect_flight
http://www.nurseminerva.co.uk/adapt/insect.htm
Wing movements through the air
As the wings move through the air flapping, the wings are deflected through the air. You can see it in these two high speed movie of flies flying:
Flies flying:
http://www.arkive.org/house-fly/musca-domestica/video-00.html
Check out the movie below to see how a wing is deflected in the air from the laboratory of Tom Daniel:
Flapping wings:
http://faculty.washington.edu/danielt/Wingmovies.html
When the wings are moved under different conditions, such as helium, the wing does not move in the same way, in that, in air, the wing can form the vortices
Under different air conditions:
http://faculty.washington.edu/danielt/vacbox.html
Thoracic wing musculature
Wing musculature: direct flight muscles
Dragonflies also move their wings in an alternating pattern, which is controlled through direct flight musculature.
http://en.wikipedia.org/wiki/GNU_Free_Documentation_License Taken by Fir0002, flagstaffotos.com.au, Wikimedia Commons
Wing musculature: indirect flight muscles
Basic motion of the insect wing in insect with an indirect flight mechanism.
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Dimensions of movement in flight
Insects can rotate through three different axes, which includes pitch (up/down), yaw (side to side), and roll (roll around the front). In addition to these three dimensions of movement, insects can move forward (translate), and slip sideways. Considering these different types of movements, insects have to detect when changes in movements along the wing and wing base as well as use visual feedback (see Eyes & Vision module) .
Sensory input from the wing
On the wing itself, there are campaniform sensilla, setae, hairs, and sensilla to detect deflections of the wing. There are nerves mostly in the base or in the thicker veins of the wing.
The halteres: what they do
- Halteres are a modified pair of wings, which is on the metathorax in the order Diptera and on the mesothorax in the order Strepsiptera.
- The halteres are gyroscopes, where they can detect accelerations about the yaw axis<
- The halteres flap at the same frequency of the wings (up and down)
- When the insect suddenly moves in the yaw direction, the haltere is deflected, which is detected by the mechanosensory organs at the base of the halteres
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Wiring the flight circuit
The flight circuit involves a complex integration of information from the sensory organs on the head and on the thorax as well as input from oscillators in the thoracic ganglion, which alternate between depressing or elevating (levator) the wing.
Flight stabilizationWith the help of halteres, mechanosensory organs, visual feedback, and various control mechanisms, insects can have incredible control of flight. In the two videos below, hawkmoths (Family: Sphingidae) can show incredible hovering flight, which can adapt based on visual and mechanosensory feedback: image: RedR Wikimedia Commons |
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http://commons.wikimedia.org/wiki/File:Macroglossum.stellatarum.video.ogg |
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Taking off
In taking off, flies push down their middle legs (the mesothoracic leg). video
The mesothoracic leg moving down then shifts the thoracic sclerites, resulting in the wings lifting up.
As the wings lift up, the flight musculature is engaged, resulting in the beginning of flight.
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Flight and research
To understand how insects can use stabilization, visual feedback, and various other information to move through their environments, researchers like Mark Frye and Michael Dickinson have worked to characterize how Drosophila can fly and move through the world.
Look up these movies of flies in experiments:
Mark Frye:
http://www.physci.ucla.edu/research/frye/movies.htm
Check out the videos at the Dickinson’s website to find out how flies fly:
Michael Dickinson:
http://www.dickinson.caltech.edu/Links
Researchers have also attempted to use insects and wire them up with electrodes to trigger flight patterns. Check out the video below to learn all about it:
Cyborg insects:
http://singularityhub.com/2009/03/24/cyborg-insects-take-flight/
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TOPIC REVIEWDo you know…?
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Go on to the next module: Memory and Learning