Macrotermes bellicosus

Macrotermes bellicosus is a highly organized species of termite. Its name comes from a Latin word meaning "combative." These insects are indigenous to Africa and South-East Asia.

Within a colony, members are divided into specific roles called castes. The queen is the largest known termite when she is physogastric, which means her abdomen is greatly enlarged for egg production. Workers are smaller than the queen, while soldiers are slightly larger than the workers. This complex social structure allows the colony to function as a single, efficient unit.

The worker caste is further divided into major workers and minor workers. This is known as caste polyethism, where different individuals perform different tasks. Initially, all workers stay inside the nest to care for the queen. Eventually, they leave to forage for food. Minor workers typically exit the nest between 9 and 32 days after moulting. Major workers leave slightly later, between 13 and 25 days after moulting.

Their jobs change based on the colony's immediate needs.

Division of labor is very clear during foraging activities. Minor workers handle the initial exploration phase. They build underground passages that radiate outward from the nest. Major workers remain mostly inactive during this early exploration. However, once food is discovered, the labor shifts. Major workers become the primary caste responsible for gathering food. During this time, the ratio of major to minor workers changes. The colony increases the number of major workers to handle the new resource.

Researchers have identified two distinct feeding groups based on gut contents. These groups are categorized by what they eat: the fungus comb or the queen cell. The diet affects the physical appearance of the workers. Most workers have dark brown abdomens because they feed on the fungus comb. A smaller group has reddish-brown abdomens from eating plant litter.

Major workers are the primary group consuming plant litter. Because the fungus comb is made from processed plant litter, major workers dominate both food processing and fungus comb construction.

Communication relies heavily on chemical signals called pheromones. Minor workers leave scent trails that all termites can follow for exploration. Major workers, however, can detect specific food information within these trails. This allows major workers to orient themselves directly toward food sources. Interestingly, the trails left by major workers may be antagonistic to minor worker trails. This likely prevents major workers from crowding a single food source. By making existing trails less attractive, they are encouraged to find new ones.

Environmental conditions significantly influence how these termites build their mounds. In the forest habitats of Comoé National Park, termites build dome-shaped mounds with thick walls. These thick walls help the mound retain heat in cooler environments. In the savanna, they build more complicated structures with thin walls. These thin walls allow the mounds to shed heat faster in warmer climates.

To build, termites burrow into the subsoil and collect clay. They moisten this clay with saliva to shape the structure. This construction is most labor-intensive during the wet months.

Survival strategies also change depending on the habitat and predator levels. In the forest, food is abundant, but predation risks are high. If a predator appears, forest termites immediately abandon their food. In the savanna, food is more limited, so termites value it more highly. In the savanna, they only gradually reduce foraging as predation pressure increases.

Despite the harder conditions, savanna colonies show higher lifetime reproductive success. They grow faster and produce more offspring than forest colonies. This demonstrates how environmental pressures shape the entire life cycle of the species.