Insecta  

Wings perform high-quality flight: insects
 

Wings of insects of different size perform high-quality flight by producing different flow structures as they flap.

 
  "The elevated aerodynamic performance of insects has been attributed in part to the generation and maintenance of a stable region of vorticity known as the leading edge vortex (LEV). One explanation for the stability of the LEV is that spiraling axial flow within the vortex core drains energy into the tip vortex, forming a leading-edge spiral vortex analogous to the flow structure generated by delta wing aircraft...The results suggest that the transport of vorticity from the leading edge to the wake that permits prolonged vortex attachment takes different forms at different Re [Reynolds numbers - mostly affected by insect's size]." (Birch et al. 2004:1063)
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Wings combine support and material economy: winged insects
 

The wings of insects combine structural support and material economy because they are flat, braced surfaces.

 
  "Insect wings provide yet another example of braced, flat surfaces--cylindrical cantilever beams (veins) support a thin membrane. A pound of fruit-fly wings laid end to end would stretch about 500 miles, a very low mass per unit length--a steel wire to go so far would have about the same diameter as a red blood cell. Yet in each second of flight the tip of a wing moves several meters and reverses direction four hundred times. Other paddles and fins are fairly flat as well, as are some feathers, the book gills of horseshoe crabs, and a scattering of other stiff structures. In all these cases, though, flatness suits functions other than support. From a mechanical viewpoint the flatness of these systems, however impressive, is perhaps best regarded as a necessary evil--and their designs incorporate features that offset their intrinsically low flexural stiffness." (Vogel 2003:439)
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  "Each ommatidium…consists of several basic parts. There is a layer of transparent cuticle on the outside, which allows light into a lens beneath it. This is usually surrounded by cells containing 'scattering pigment' which absorbs scattered or incidental light rays, so that the only light entering the ommatidium is directly parallel to its axis. This beam of light is directed by the lens down the narrow visual centre or rhabdom where it reacts with pigment, stimulating the nerve cells that surround the rhabdom. The nerve cells pass the message to the optical centre in the insect's 'brain' where it is interpreted…The ommatidia of different insects are varied. They may even be of different sizes within a single compound eye. The scattering pigment reduces the total amount of light entering the eye, so insects active by day may find themselves blind at dusk when the light is lower and more diffused. Nocturnal insects, however, often have the ability to withdraw the scattering pigment from their eyes at night in order to absorb every scrap of available light and to allow light from many of the lens facets to focus on a single light-sensitive rhabdom, thus increasing the effective aperture of the lens system. Many moths go even further, possessing (like cats and some other animals) a kind of mirror - the tapetum - at the back of the eye: this reflects light back through the retinal cells, so every beam of light is used twice over." (Foy and Oxford Scientific Films 1982:122-123)
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Hairs sense environmental cues: insects
 

Socketed hairs of insects detect environmental stimuli through vibration.

 
  "Most insects have socketed hairs (sensory setae) scattered over much of the body which vibrate in response to sounds and may also be sensitive to touch, humidity and light. Nocturnal insects, such as cockroaches, are particularly sensitive to sounds via their setae and have been known to shy away from vibrations issued at 3000 cycles per second--way beyond human hearing capabilities. The setae may also play other roles. Locusts use those on the head, between the antennae, to judge the direction and humidity of the breeze, and climb some eminence for this purpose. Subsequently, they may use the information thus gained to fly to areas of low pressure where rain is likely to induce lusher feeding pasture." (Wootton 1984:48)
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