If the insect in question has both complex eyes and simple eyes. the simple eyes are for close range vision while the complex eyes are primarily for longer range vision. If the insect has no complex eyes, then their simple eyes are used best they can for all around vision.
The function of an insects simple eyes is to see. This is the function for eyes on most living creatures.
There are many different things that could be considered a simple eye. Many insects for example have simple eyes because they serve one purpose.
It's a tricky question because insects have two kinds of eyes. There are simple eyes and compound eyes. Some insects just have one type, others have both types. The simple answer is, most insects have two eyes, but several of them have five eyes.
Insects have Compund Eyes.
Insects have a separate head and thorax whereas spiders have a combined head and thorax, known as the cephalothorax. Insects also have compound eyes while spiders have simple eyes.
simple eyes, compound eyes tracheae
The simple eyes also called ocelli are only used to detect light intensity and not for seeing.
Hornets have two compound eyes and upwards of about three rudimentary ocelli, or simple eyes, which are simple eyes that traditionally pick up light/dark variants to accompany the compound eyes in many flying insects.
Insects can have a number of eyes and moreover, eyes of different types; single eyes and compound ones. In contrast with our eyes, insect eyes are immovable and unable to focus. Insects are short sighted. Butterflies are probably the most far sighted, they can see perhaps a few meters, while bumblebees only have a range of a half meter. But many insects are helped a lot by their sometimes unbelievable sensitivity for scents.
Probably dragonflies, with as many as 30000 facets in each of their compound eyes.
simple eyes means that they see the way that we do, through a set of eyes.Compound eyes means that they see through many lenses set in one eyeball, allowing sight from many directions.Many flying insects possess this characteristic.Two eyeballs,many lenses.
Light-sensitive ocelli occur in some insects and spiders. Ocelli eyes are referred to as simple eyes that can tell the difference between light and dark.
Fleas don't possess compound eyes but they have only simple eyespots with a single biconvex lens & Spring tails have two eyes, but these two are actually clusters of up to 8 single eyes but they are not technically compound eyes.