House fly at rest.
A house fly takes off vertically into the air.
While snapping pictures of a fly perched beside me during a long car drive I caught a shot of it in mid take-off, as it launched straight up into the air. I’d never given a lot of thought to house fly flight dynamics before, except perhaps during miserably failed attempts to swat them. Attempting to learn more on the topic led me to a fascinating article discussing the use of insects to develop flying nano-robots, aka Micro air vehicles.
Obviously, I want one of these.
A tiny, insect-inspired flying machine (photo: Wood 2008).
But instead of talking about tiny flying robots being harnessed for military purposes I thought I’d tell you some boring fascinating stuff about insect flight muscles. The oldest insects (Paleoptera: dragonflies, damselflies, and mayflies) have muscles directly attached to the base of the wing (direct flight). The fore and hind wings are operated independently, allowing for excellent mobility and maneuvering. All later insects (Neoptera) have muscles that attach to the exoskeleton, and move the wings indirectly by changing the shape of the thorax (indirect flight). Generally, the wings function together as a single unit.
Because I was bored, I diagrammed the muscles involved in indirect flight:
The dorsoventral muscles contract, pulling down the top of the thorax and causing the wings to rise.
The dorsolongitudinal indirect flight muscles contract, arching the top of the thorax and causing the wings to beat downwards.
If you have trouble visualizing how flexing the exoskeleton in these directions could lead to the appropriate wing movements, I recommend this simple experiment: Take a tennis ball, and stick two pins in it to represent the wings. Squeeze the tennis ball from top and bottom (dorsoventral muscles) and from front and back (dorsolongitudinal indirect flight muscles) and observe the movements of the pins. We did this back in my Insect Physiology class, and it makes for a very striking visual tool.
Wikipedia also has two very useful animations (the direct flight diagrams is mislabeled, though, so mind your links):
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