Well if you’re a flying insect (like this rather light headed hornet I found dead on the ground earlier today), more than you might imagine.
Insects, especially those that fly, have some of the most captivating and fantastic eye structures. These compound eyes, so different from our own, allow for rapid image detection in a range of spectral frequencies (even into the UV) and the capacity to undertake the truly breath-taking aerial acrobatics we witness when trying to forlornly swat the irritating buggers from the air.
BUT, did you know that these at not the only eyes insects (especially those that fly) posses?
They also have a triple array of very rudimentary eyes called ocelli between their main eyes.
These eyes are not terribly acute, they cannot focus independently, in fact their fixed focal length cannot focus clearly onto their retina at all. So why have three extra eyes if they are fundamentally useless?
Because they actually serve a unique purpose, they allow that insect to establish pitch, roll and yaw if the insect is unexpectedly knocked or blow off course, by comparing the light intensity between themselves…
But then I hear you cry, “Why not just use your complex and highly acute compound eyes for that?!”
Well they do, but you have also answered the question in a way. Because these larger eyes are more complex they take longer for the insects brain to process information, and therefore reaction speed is compromised, which when you’re an insect the size of a pea hurtling through the air like Concorde is probably a pretty big deal.
So there you have it, sometimes even flies need to KISS (Keep It Simple, Stupid) in order to stope themselves getting turned about.