Pencil caterpillars, also known as pencil larvae, are the larval stage of certain moth species, particularly from the family Geometridae. They are named for their elongated, slender shape, resembling a pencil. These caterpillars often have a green or brown coloration, which helps them blend into their surroundings, making them less visible to predators. These caterpillars are primarily herbivorous, feeding on the leaves of various plants. As they grow, they undergo several molts before transforming into pupae and eventually emerging as adult moths. The life cycle of pencil caterpillars is an essential part of the ecosystem, contributing to the food web and plant pollination.