Of all the things that fly, Insects are possibly the least understood. Their small size and quick movements have made them much more difficult to study, and much of the research about insects has not yet become widely known. One such piece of knowledge that has not yet become common knowledge is the phenomenon of indirect flight.
Summarized, indirect flight involves the use of muscles that contract the thorax of the insect in question. The wings are raised by the contraction of the muscles (dorsoventral) attached to the upper and lower sections of the insect thorax. This contraction forces the top of the thorax down which in turn pivots the tips of the wings up. To lower the wings the muscles (longitudinal) attached to the front and rear of the thorax contract forcing the top of the thorax back up which lowers the wings.
Insects that utilize indirect musculature include the common housefly as well as other Diptera. (The order of insects that includes most flies). While this system indirect control might sound complicated to an outside observer, in reality it is the opposite. The flapping motion utilizing the indirect method requires very few messages from the brain to sustain flight which makes it ideal for tiny insects with minimal brainpower. In addition to the low brain power required, indirect flight muscles allow for extremely rapid wing movements. Some gnats can beat their wings as fast as 1000 while common houseflies achieve 200 times a second. These rapid wing beats are required for insects of such small size as their relatively tiny wings require extremely fast flapping to maintain adequate lift forces.
The simplicity of the system and the rapid wing beats come at a price. Indirect flight muscles do not allow for as much finesse as directly controlled wings do as the wings are not able to be fine-tuned as much. For small insects like flies this doesn’t matter as the rapid wing beats alone are more than able to provide enough maneuverability for these small insects to get by, but larger animals with greater mass might not be able to cope with the drawbacks quite as well.
As far as utilizing this knowledge in the engineering field, the concept of indirect flight muscles might be useful in the creating of ultra small uav’s. Since the processing power to control the indirect flight muscles would be so low, very small chips could be utilized allowing the vehicle to be scaled down to essentially the size of an actual fly. At that size, the uav would be virtually undetectable allowing for a wide range of uses.