Caterpillar – Anatomy

Caterpillars come in many colours, shapes, and sizes. Some caterpillars are quite hairy, while others are smooth. Regardless of these varied features, all caterpillars share certain morphological features. Caterpillars have a segmented body consisting of a head, a thorax (with three pairs of jointed legs with hooks), and an abdomen (usually with five pairs legs). The head includes the eyes, the mouthparts, the small antennae, and the spinnerets, from which the caterpillar produces silk. Caterpillars have six pairs of simple eyes that can detect changes in light intensity, but cannot form an image. The maxillae also have taste cells; these chemical detectors tell the caterpillar to eat when the food is appropriate, and not to eat when the food is not appropriate. The tiny antennae, which are near the mouth parts, sense smells. The legs are used primarily for holding and manipulating the leaves on which they feed. However, not all caterpillars have this same distribution of legs. Caterpillars breathe through oval spiracles which open and close to allow gas exchange with the atmosphere. There are 2 spiracles per body segment, one on each side of the body.