Wasp On Deck Applied Physics

Two summers ago, I was eating fruit in the sun when I noticed that a wasp had found a fragment of my pear on the deck. The piece was only about a centimeter cubed in volume but heavy enough to prevent the wasp’s takeoff. Soon after its unsuccessful straight-up takeoff attempts, the wasp dragged the little pear morsel across the deck for about two and a half meters until it reached the edge. Once off the deck, the wasp was able to fly away with its meal.

By observing the wasp, I was reminded that anything trying to take off vertically needs a lot more of its own force to get off the ground than to propel itself in flight. (When flying, the circulating air mass around the wasp helps it overcome gravity.) A study (Dial, Kenneth B. J. exp. Biol. 176, 31–54 (1993)) done on the liftoff force generated by pigeons concluded that the birds had to develop, in using their legs and a clap and fling mechanism, an upward directed force as high as 2 to 3 times their body weight.

I could not find anything on insects, but let’s assume that a wasp is also capable of developing an upward force of up to two to three times its body weight. The mass of the pear is somewhere between 0.6 and 1 gram (the pear is mostly water with a density of 1g/cm3). But the average mass of a wasp is only about 90 mg. Even if it could generate an upward force three or even five times its weight, it would still fall short of the force needed to directly ascend upwards with my pear.

With rotary motion which is more efficient than the mechanism of birds and insects, helicopters also takeoff vertically. The largest cargo helicopter, the Mi-12, has a maximum takeoff weight of 231 500 lbs. But the Antonov An-225 Mriya, which like most planes takes off at an angle slightly raised from the horizontal, has a maximum takeoff capacity that’s about six times bigger.  With the pear, the wasp failed to take off vertically, so it turned my deck into a runway.

It’s interesting how the wasp first tried to takeoff in its usual way, which is a practical strategy when it has to fly off a flower or off a paralyzed insect whose fluids it has sucked away. But what went on its brain as it solved the problem of how to fly off with a heavy meal?

It’s no wonder that parts of their brain grow in size after they are repeatedly engaged in complex tasks. Wasps have also been known to pick up competitors(ants) who were eating their food, fly off with them and then dropping them at a distance. Since the ants are much smaller in size, the wasps, in this case, don’t have to combine their airlift behavior with a runway-strategy.

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