Simple eyes or dorsal ocelli:

• Two types of “simple eyes” can be found in the class Insecta: dorsal ocelli and lateral ocelli (=stemmata). Although both types of ocelli are similar in structure, they are believed to have separate phylogenetic and embryological origins.
• Dorsal ocelli are commonly found in adults and in the immature stages (nymphs) of many hemimetabolous species.
• They differ from compound eyes in having only a single corneal lens covering an array of several dozen rhabdom-like sensory rods.
• Lateral ocelli (=stemmata) are the sole visual organs of holometabolous larvae and certain adults (e.g. Collembola, Thysanura, Siphonaptera, and Strepsiptera).
• Larvae use these simple eyes to sense light intensity, detect outlines of nearby objects, and even track the movements of predators or prey.