8 Novembe 1999

Arthropod locomotion: Flight--General principles and mechanics
 

Principles

flow over a surface is either laminar or turbulent or both. Rough surfaces produce turbulence and thus causes frictional drag to occur.
pressure fields--are produced by the fact that the air flows are at different velocities

lift--produced by difference in pressure as air moves over a foil

direction of lift is related to orientation of foil surface. for examples, bees change the orientation of their wings to either hover, go forward or go in a reverse direction. Thus a propeller is really an air foil, but oriented in a forward direction rather than upward.

Aspect ratio--measure of the chord to the width of a wing. Hawk moths have short triangular shaped wings that produce little lift and must be flapped rapidly. Other insects, eg. some grasshoppers have long wings that provide lots of lift and facilitate gliding.

Check out the UC-Berkeley page for more info on vertebrate flight (many of the principles apply in insect flight)

Mechanics

Exoskeleton in thoracic region is composed of two parts, dorsal and ventral components hinged at their juncture. Insect uses dorso-ventral muscles and longitudinal muscles to change the configuration of the exoskeleton. Since wings are at the junction between the two, they are moved up and down as the exoskeleton changes its confirmation.

Small muscles attached to the base of the wings, change their aspect.

Beating of wings is controlled by the nervous system. That wing beat frequency is often greater than nerve stimuli indicates that the system has a built in capacity to continue beating even if no stimulus is present. This is due to the elastic component of the system which is progressively deformed and then returns to its undeformed state.

Morphology

Two pairs of wings, fixed, not foldable (dragon flys)

Two pairs of wings, both work in same pattern (many insects)

Two pairs of wings, one functional, the other not (beetles--elytra and membraneous wing)

One pair of wings, the other replaced by halteres (flies)

Wings not foils, but feathers (gnats)

Patterns of flight

Gliding flight--butteflies, grasshoppers

Powered flight--hovering moths, bees, insects.

Using the viscocity of the air and rowing oneself through the air