Termites shed their skin, undergoing a process known as molting or ecdysis. As social insects, termites belong to the phylum Arthropoda, characterized by a rigid external skeleton called an exoskeleton. This hard outer covering provides protection and support but cannot expand to accommodate growth. Consequently, a termite must periodically shed its old skin to increase in size and progress through its life cycle. This biological necessity is a fundamental mechanism shared by all insects and arthropods that grow in discrete stages.
The Necessity of Shedding Skin
The need to shed skin arises because the termite’s cuticle, which is composed partly of the tough substance chitin, is inelastic. To grow, the insect must first separate its body from the old exoskeleton, a process called apolysis, and secrete a new, soft cuticle underneath. Enzymes are released to digest the inner layer of the old skin, allowing for this separation.
Once the new skin is ready, the termite takes in air or water to increase its internal body pressure, causing the old exoskeleton to split. The termite then slowly pulls itself out of the discarded shell. This period, immediately after shedding, is called the teneral stage, where the termite is pale, soft, and highly vulnerable until its new skin hardens and darkens.
Molting is a hormonally triggered event. The process is physically demanding and leaves the termite defenseless, which is why molting typically occurs deep within the safety of the colony.
How Molting Drives Termite Caste Development
Molting in termites is more complex than simple growth; it is the mechanism that allows for caste differentiation, which is the assignment of specific roles within the colony. Termites are hemimetabolous, meaning they develop through a series of molts from a nymph stage. Each molt is an opportunity for the individual to change its developmental path, as all nymphs are genetically capable of developing into any of the major castes—worker, soldier, or reproductive.
The nymph’s final destination is regulated by the colony’s needs and a sophisticated system of chemical signals. Pheromones, shared through food-sharing and grooming, play a regulatory role by inhibiting the development of certain castes. For instance, a queen secretes inhibitory pheromones that suppress the molting of nymphs into new reproductive individuals.
If a queen or a soldier dies, the supply of their specific inhibitory pheromone decreases, signaling to the nymphs that a new individual is needed. The next molt for an uncommitted nymph can then lead to a specialized form, such as a soldier with an enlarged head and mandibles, or a reproductive swarmer with wings.
What Remains After Molting
The physical remnants of the shed skin are called the exuviae, the hollow, cast-off shell of the old exoskeleton. Termites exhibit a unique behavior by consuming their own or their nestmates’ shed skin immediately after molting. This consumption serves multiple purposes beneficial to the colony’s survival.
The exuviae are rich in protein and chitin, making them a valuable source of nitrogen, a nutrient often scarce in the termite’s primary diet of wood. By eating the shed skin, the termites effectively recycle this nitrogen back into the colony’s nutrient pool, which is important for reproductive growth. This behavior also serves as a sanitation measure, ensuring that no waste materials are left behind to attract predators or harbor pathogens.
For lower termites that rely on symbiotic microorganisms in their gut to digest cellulose, the molting process often results in the loss of these gut fauna. Consuming the exuviae and engaging in proctodeal trophallaxis (the sharing of hindgut fluids) helps the newly molted termite quickly reacquire the necessary microorganisms to resume digestion.