Unraveling the Mysteries of the Structure and Evolution of Insect Societies

There are many kinds of organisms on Earth, and some of them live in societies. Eusocial insects, such as honeybees, ants, and termites, are known for forming particularly complex societies. Focusing primarily on termites, I study how they form their societies and how these societies have evolved.

Termites form societies by gathering with individuals of the same species and engage in a division of labor. In this division of labor, each individual within the society specializes its body shape, behavior, and physiological state to efficiently perform specific tasks. For example, the queen and king develop reproductive organs such as ovaries or testes to focus on reproduction, and they receive food from worker ants through mouth-to-mouth feeding. Soldier ants, to fight off enemies, have parts of their mouthparts (mandibles) develop into fang-like structures, while their reproductive organs do not develop, and they do not reproduce. Furthermore, due to the modification of their mouthparts, soldier ants cannot chew their own food and receive it from worker ants via mouth-to-mouth feeding. Worker ants perform various tasks such as foraging, feeding others, caring for the young (nymphs), and nest construction, but they do not reproduce. Each individual termite's body is so specialized that it can no longer survive on its own. They live as members of the society, complementing each other.

A termite society is a collection of individuals performing different functions, and only when they come together do they possess all the functions of a single, solitary organism. The constituent individuals of a termite society can number in the millions depending on the species, but through close coordination, they exhibit remarkably controlled collective behavior. This behavior makes them appear as if they were a single organism. For this reason, a termite society is described not merely as a group or a swarm, but as a "superorganism."

The coordinated cooperative behavior among individuals creates a significant synergistic effect, and as a result, the superorganism exhibits astonishing productivity. Because of this high productivity, termites have succeeded in thriving on Earth.

The existence of "castes" is essential for the formation of a termite superorganism (society). A caste is a group of individuals that performs a specific role, such as queens, kings, workers, or soldiers. Individual termites all have the same form at birth, but during their subsequent development, their bodies change, and "caste differentiation" occurs, with some differentiating into workers and others into soldiers. By properly controlling the caste differentiation of individuals, a balanced caste ratio—in other words, an efficient division of labor system—is achieved in the termite society.

So, how is the caste of each individual determined? I have been working on this problem and have revealed that caste is determined by the influence of "genetics" and "pheromones emitted by the queen." However, not everything has been clarified. What kind of genes are involved in determining an individual's caste? To what extent do those genes influence caste determination? What substances are the queen's pheromones? Besides these, there are still many things we do not know. I hope to unravel these mysteries one by one.

DNA (deoxyribonucleic acid) is the genetic material that organisms possess, and it holds a vast amount of genetic information. Often called the "blueprint of life," DNA contains the information necessary to form an organism. Therefore, by analyzing the genetic information in DNA, the unknown characteristics of that organism can also be revealed. By comparing the genetic information of multiple species, we can clarify their differences and also what evolutionary traits have emerged in each species.

Termites, which are eusocial insects, evolved from solitary ancestral insects via subsocial ancestral insects (which have the characteristic of raising their young). So, what characteristics of those ancestral insects evolved to give rise to eusocial termites? To answer this question, I am analyzing the genetic information of termites and other organisms. Analyzing this vast amount of genetic information is not easy, but through this analysis, I hope to clarify the evolutionary process of termite societies.