Mosquitos (Anopheles gambiae) go through four stages of their life cycle: egg, larvae, pupae (as shown) and imago (=adult insect). Adult females lay their eggs in standing water. The first three stages are aquatic and last 5–14 days, depending on the species and temperature.
The pupa is comma-shaped, as in Anopheles when viewed from the side, and is commonly called a “tumbler”. As with the larvae, pupae must come to the surface frequently to breathe, which they do through a pair of respiratory trumpets on the cephalothorax. After a few days, the pupa rises to the water surface, the dorsal surface of the cephalothorax splits and the adult mosquito emerges.
In the course of the metamorphosis, the eye is subject to drastical differentiation and structural change. While the larva is spending most of its time feeding on algae, bacteria, and other microbes in the surface microlayer and only possess a pit-eye ocellus, the compound eyes of the pupae and adult are distinctly separated from one another and much more developed. Similar to other flying insect species, they are the dominant sensory organs for flight orientation in the adult.