Eyes and Ocelli
عيون وعيون بسيطة
Most insects have two large compound eyes, each with up to thousands of independent lenses that enable a wide angle view and fast motion detection. In addition, most insects have three small eyes called ocelli, each with a single lens. Ocelli are most noticeable on wasps where they form a triangle on the top of the head, but they are also present on most invertebrates. Crickets have only two ocelli. Some insects and larvae have 2-12 lateral ocelli on the sides of the head. In general, ocelli are simple remnants of evolution that barely detect light. In some insects such as dragonflies, ocelli serve as horizon detectors to maintain stability in flight. In desert ants, ocelli function like a compass, reading information from the sky to detect direction (see Desert Ants).