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When wasps, bees and flies continually clatter against the glass of my conservatory in an attempt to escape, are they following a strategy?
Stefan Badham
Portsmouth, Hampshire, UK
Flying insects that have entered a building are following no specific strategy when they repeatedly clatter against glass.
The directions taken by flying insects can often be dictated by external air currents. While flies can be transported on these currents into a building through an open window or door, they will rarely, if ever, perform a return flight via the same route to get out. That is because the air currents on which they travel are mainly outside the building, with each current moving in a certain direction, which is why curtains are mostly blown by the air coming in through an open window, but seldom by the air within when the window is shut.
Flies probably don’t have a concept of glass (to them, it is simply impenetrable air), which is why they repeatedly and unsuccessfully try to pass through it.
If you open a window fully to let a fly out, in most instances it will fly everywhere except through the opening itself. That is because the air currents from outside are pushing against the fly, effectively keeping it from flying outside. Flies don’t fly against air currents. Instead, they are carried forwards and along by them.
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