|MadSci Network: General Biology|
The most basic reason is the same as why don't you die standing, you may die standing but you fall over. The same is true for insects. The may die standing on a wall, floor, or ceiling, but they won't stay standing. They either fall over, or are blown by a gust of air and thus blown off their feet. Unlike humans which can fall over on their belly or their back, insects pretty much only have their back to fall over on since there feet are often under their belly.
Best Wishes, David Beck
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