Insects :



                The complexity of the wing motion of insects is an active area of research.  Most of the physics that is very handy to fruit-flies, is still elusive to human understanding.


        Although some of the basic aerodynamics associated with bird flight are also applicable in case of insects, there are many features very unique to these small flyers.


1)        Insects fly at a much smaller Reynolds number as compared to birds. Their low flight speed is responsible for this, as is indicated in the following table

Insect	Speed in m/s
Mosquito	0.5
Honey bee	3
Desert locust	4.4
Dragonfly	7.5
Deer botfly	9

2)        Gliding motion is occasionally observed, mostly in case of larger insects - the swallowtail butterfly, for example.


3)        Hovering is the most common wing motion found in flying insects - with the “figure of 8” trajectory superimposed with further complex motion. During hovering, wing beat frequencies can be extremely high - as the following table  suggests.

Insect	Frequency of Wing Beat (Wing beats / second)
Desert locust	20
Dragonfly	35
Honeybee	200
Mosquito	300

We have all enjoyed, or have been annoyed, at some time or the other, by the humming sound of a bee, or the monotonous sound generated by mosquitoes.  The reason we can hear many insects flying is because the high frequency of their wing beats makes it audible to the human ear.