Sensory Systems
The insect head bears a single pair of compound eyes, composed of many individual units, called ommatidia, each of which senses a small portion of the visual field. Hunting insects such as the dragonfly may have thousands of ommatidia per eye, while others, such as ants, have many fewer. A single pair of antennae serves as chemical sensors to help find food or mates. In many species, including the tobacco hornworm moth, the female releases airborne chemicals called pheromones that attract the male. The highly branched antennae of the male moth can detect the molecules of the female pheromone, and can track the scent to find the female over very long
A katydid. Insects are distinguished by having three major body segments (head, thorax, and abdomen), with three pairs of legs attached to the thorax.
distances. Chemoreceptors are also located on the feet, allowing an insect to taste its food as it walks across a leaf or a table. The numerous hairs covering the insect body are linked to mechanoreceptors, which aid its sense of touch. Some mechanoreceptors can sense changes in air pressure, useful for flying or evading a swooping predator. Receptors for carbon dioxide, water, and temperature also exist.