The head of insects contains most of the sensory organs. Like all insects, caterpillars have one pair of antennae and they are involved in chemoreception, the sense of smell. The caterpillar antennae arise from small sockets on the front of the head. The antennal nerves connect directly to the olfactory lobe of the caterpillar brain. Unlike adults, that have much longer and often more elaborate antennae, the antennae of caterpillars are short and threadlike.
The antennae and the palps contain the majority of odor receptors in the caterpillar. Removing the antennae of caterpillars (with very tiny scissors) has little effect on survival. Caterpillars without antennae may feed more reluctantly on plants that are readily accepted by intact caterpillars. Caterpillars without antennae may more frequently begin feeding on some plants that are typically rejected by intact caterpillars. Thus, caterpillars antennae are important in directing the feeding activity of caterpillars.
Not all of the functions of caterpillar antennae are known. Antennal removal experiments suggest that caterpillars use their antennae to gather information about their environment, but have mechanisms to compensate if the antennae are missing. The utility of caterpillar antennae is incompletely understood. However, for most situations, the antennae are of minor importance. Caterpillar eggs are typically laid on suitable food plants by Mom. The caterpillar may spend its whole life on a single plant and have no need to decide if the plant it is on is food or not. Caterpillars that move from plant to plant may have more uses for their antennae.
Image of the head capsule of a caterpillar from below showing the antennae (arrows) on the front of the head.
