Why termites are called eusocial insects
Termites, sometimes known as white ants, are a group of eusocial insects usually classified at the taxonomic rank of order, Isoptera.
Termites feed on dead plant material, generally in the form of wood, leaf litter or soil, and about 10% of the 4,000 odd species (about 2,600 taxonomically known) are economically important as pests that can cause serious structural damage to buildings, crops or plantation forests.
Termites are significant detrivores, particularly in the subtropical and tropical regions, and their recycling of wood and other plant matter is of considerable ecological importance.
As social insects, termites live in colonies that, at maturity, number from several hundred to several million individuals.
They are a prime example of decentralised, self-organised systems using swarm intelligence and use this cooperation to exploit food sources and environments that could not be available to any single insect acting alone.
A typical colony contains nymphs (semi-mature young), workers, soldiers, and reproductive individuals of both sexes, sometimes containing several egg-laying queens.
Because of their wood-eating habits, termites sometimes do great damage to buildings and other wooden structures.
Their habit of remaining concealed often results in their presence being undetected until the timbers are severely damaged and exhibit surface changes.
Once termites have entered a building they do not limit themselves just to wood, also damaging paper, cloth, carpets, and other cellulosic materials.
- Why termites are called eusocial insects
- What Are Social Insects?
- There are varying degrees of social behavior among insects
- Advantages of Social Behavior in Insects
- Characteristics of Social Insects
- Degrees of Sociality in Insects
- Subsocial Insects
- Communal Insects
- Quasi-social Insects
- Semi-social Insects
- Primitively Eusocial Insects
- Table of Sociality in Insects
- Introductory Case: Life of termites as eusocial insects
- The Termite Colony.
- Kinds of Termites.
1. The mother, along with individuals that may or may not be directly related, conducts cooperative care of young.
2. A reproductive division of labor evolves from sterile castes which often have certain propensities or characteristics associated with helping behavior.
3. There is an overlapping of generations which allows for the older generations of offspring to help related, younger generations.
Table 1: Examples of Eusocial Insects
|Ants||All ants are eusocial. |
They have morphologically
distinct workers and queens.
In some ants, the workers
do not even have ovaries.
Other workers can lay male
|Fire Ants, Solenopsis invicta |
Pharoahs ants, Monomorium minimum
Carpenter Ants, Camponotus
Pseudomyrmex in acacia galls
Leaf Cutter Ants, Atta
|Bees||Many bees are not |
social at all.
|Sweatbees, Lasioglossum |
Honeybees, Apis mellifera
Carpenter Bees, Xylocopa
|Wasps||Some wasps are eusocial, |
but many are not.
|Paper Wasps, Polistes |
Tropical Wasps, Epiponines,
|Termites||All termites are social. |
They have male and
female workers and,
unlike most social
insects. are diploid
rather than haplodiploid.
Often they have a king
and a queen.
|Aphids and Thrips||Some aphids and thripes
are are eusocial. When
they form a gall, some
soldiers will not
reproduce. This form of
eusociality tends to be
restricted to a few soldiers,
because the sterile forms
only defend and do not
care for the young.
Therefore, there is less
potential for the development
of advanced societies.
Relatedness and the Origin of Eusociality
M any eusocial insects, including ants, bees, and wasps, are haplodiploid. Therefore, each female has two alleles at a locus, while each male has only one. This leads to a different kin relatedness than that which diploid species exhibit. For example, whereas a diploid female is related to her sister only 1/2, a haplodiploid female is related to her sister 3/4. Other degrees of relatedness are charted below:
Table 2: Genetic Relatedness in Haplodiploid and Diploid Species
T he relatedness differences in haplodiploid species lead to differences in their display of kin selected behavior as compared to diploid species. On the basis of kin selection, eusocial females would be expected to prefer to help their mothers raise their sisters, increasing their indirect fitness, rather than concentrating on increasing their direct fitness by raising their own offspring. This explains why there are sterile castes in eusocial insects; these workers may give up potential direct benefits associated with raising their own children, because indirect benefits are so beneficial. The indirect benefits preference in social wasps can be used as a basis of comparison and analysis of the balance of indirect and direct benefits in other species.
D ifferences in genetic relatedness among the various individuals within a eusocial colony also make social insects important in the study of parent-offspring conflict. As mentioned above, female haplodiploids benefit from helping raise their sisters which they are related to 3/4. These females, on the other hand, are related to their brothers only 1/4. Therefore, they will prefer for their mothers to have daughters. Since the mother is related to both sons and to daughters 1/2, she will have a tendency to not show preference towards daughters, leading to a conflict of interest between the mother and her daughters.
What Are Social Insects?
Animals & Nature
The true social insects—all ants and termites, and some bees and wasps—comprise 75 percent of the world’s insect biomass, according to E.O. Wilson. A colony of social bees can number in the tens of thousands, and hundreds of millions of ants can live together in a supercolony of interconnected nests.
So what makes social insects behave the way they do? There are several theories, as well as varying degrees of social behavior.
Advantages of Social Behavior in Insects
Why have some insects evolved to live in large, cooperative colonies? There’s strength in numbers. Social insects gain several advantages over their solitary cousins. Social insects work together to find food and other resources and to communicate their findings to others in the community. They can mount a vigorous defense of their home and resources when under attack.
Social insects also can outcompete other insects, and even larger animals, for territory and food. They can quickly construct a shelter, and expand it as needed, and they can divide chores in a manner that ensures everything gets done expeditiously.
Characteristics of Social Insects
So how do we define social, when speaking of insects? Many insects exhibit social behaviors, such as aggregating in large numbers at times. Gregarious behavior does not, by itself, mean an insect is social.
Entomologists refer to true social insects as eusocial.
By definition, eusocial insects must exhibit all 3 of these characteristics:
To give an example, think of termites. All termites are eusocial insects. Within a single termite colony, you will find individuals at various stages of the termite life cycle.
Generations of termites overlap, and there is a constant supply of new adults prepared to assume responsibility for the colony’s care. The community cares for its young cooperatively.
Termite communities are divided into three castes. The reproductive caste is comprised of a king and queen. The soldier caste of both males and females is specially adapted for defending the colony. Soldiers are larger than other termites and are sterile. Finally, the worker caste consists of immature males and females that do all chores: feeding, cleaning, construction, and brood care.
Solitary insects, by contrast, don’t exhibit any of these social behaviors.
Degrees of Sociality in Insects
As you may realize by now, many insects don’t fit in either category. Some insects are neither eusocial nor solitary. Insects fall somewhere on a spectrum of sociality, with several degrees between solitary and eusocial.
Just a step above solitary insects are the subsocial insects. Subsocial insects provide limited parental care to their offspring. They may shelter or guard their eggs, or even stay with their young nymphs or larvae for a time.
Most subsocial insects don’t use nests to shelter their young, though there are exceptions to this rule.
Giant water bugs fall into the subsocial group. The female deposits her eggs on the male’s back, and he is charged with protecting and caring for the offspring until they hatch.
Communal insects share a nest site with others of the same generation. This social behavior may be exhibited in one particular stage of the life cycle, such as in the larval stage of some moths. Communal insects use sophisticated forms of communication and gain certain advantages from nesting together. Communal living may help them avoid predation, assist them with thermoregulation, or enable them to find and use resources more efficiently.
Communal insects never share in caring for offspring, however. Tent-making caterpillars, such as the eastern tent caterpillars, build a communal silk tent, in which they all shelter.
They share information about food sources by creating chemical trails, allowing their siblings to follow the scent to its location.
A slightly more advanced form of social behavior is exhibited by quasi-social insects. These insects do exhibit cooperative care of their young. A single generation shares a common nest. Certain orchard bees function as quasi-social groups, with multiple females sharing a nest and caring for their young together. Though all the bees share in brood care, not all bees lay eggs in the nest cells.
Semi-social insects also share child-rearing duties with other individuals of the same generation, in a common nest.
As in true social insects, some members of the group are nonreproductive workers. However, this generation will leave their nest before the next generation emerges. The new adults will disperse and construct new nests for their offspring. For example, paper wasps are semi-social in the spring, with nonreproductive workers helping expand the nest and tend to the brood in a new colony.
The sole difference between eusocial insects and primitively eusocial insects lies in the sterile worker caste. In primitively eusocial insects, the workers look the same as queens, with little or no morphological differences between the castes. Some sweat bees are primitively eusocial.
Bumblebees, for example, are also considered primitively eusocial, although they’re an unusual example in that the queen is slightly larger than her workers, and therefore can be differentiated.
Table of Sociality in Insects
The following table illustrates the hierarchy of sociality in insects. The chart ranges from the lowest degree of sociality (solitary insects) at the bottom, to the highest degree of sociality (eusocial insects) at the top.
In my introduction to the concept of emergence, I talked about termites and other eusocial insects as one of the best examples of emerging intelligence. With the term emerging intelligence I mean a robust, adaptable, and complicated mind emerged from the interaction of simple minded entities.
In the above photo, you can see various structures made by termites. Actually these are the cities they live in. Every single colony can have millions of members. Considering the structure, scientists believe that the complexity level of these colonies is close to a mid-size city.
But before talking more about termites, would be better to make a definition of the term eusocial insects and eusociality.
Any insect species that are living together can be called social insects. But the term eusociality (originally coined by Suzanne Batra) means the most complicated social system among insects recognised by three basic characteristics:
There are various eusocial insect species which ants, bees and termites are most studied ones. But termites are more interesting as some of them build their cities not under the ground but over the ground just like our skyscrapers.
Living for about 300 million years on the earth, although they have been breakfast of dinosaurs, their robust society structure gave them the chance to see their extinction and even chances are high that they see extinction of human species. Currently, the total weight of the termites is more than the total weight of the humans on the planet. Every single termite lives for several years. But termite colony lives for even more than one century.
So if we consider survival as the most important desire of all the species (including humans) seems that termites have been more intelligent to find a practical solution for this quest.
Still considering an individual termite, it has one of the simplest minds ever existed on earth. But considering the termite society, there’s an emerged mind more complicated and more productive than human mind. No centralized government. Not any sign of democracy. Not any means of complicated communication tools or message broadcasting services. But making the best decisions:
Yes. We can be proud that we are more conscious than termites. But, to be honest, there’s no proof for that. As the ability to speak is not a proof of conscientiousness. and tool making is not a proof of intelligence if it can not help our society to live longer. Sure if aliens with no human bias come to the earth and observe us for a long period of time they will vote for termites as a more powerful and adaptable entity.
How does it happen? With a very clear and simple structure. They have three different categories with different duties in the society called castes:
Image Source:В Cozypad
Termite society is the best demonstration of the emergence concept. Simple minded individuals (we call them agents) do a very simple duty (we call it task or interaction) for the society (we call it a system) and the new characteristics emerge. The ones who has no similarity to the basic characteristics of agents.
The most complicated emergence case we ever recognized is the human brain. Individual neurons with simple characteristics combined together and a complicated system emerged which we call it brain.
To be more precise, a complicated system is emerged and called itself brain. As the brain is the only existing entity who named itself.
In future articles, I will try to show you that the brains are not the most complicated emergent system anymore. We have more complicated living digital entities which are not recognised as most intelligent and adaptable living entities of the world yet!
All members of the order Isoptera are eusocial insects. Termites feed primarily on the cellulose and lignin found in plant cell walls; these compounds are the main ingredients of wood and all paper products. Termites cannot digest the cellulose directly so they rely upon symbiotic bacteria and protozoa living within their intestines to supply most of the enzymes needed for cellulose digestion. Termites are sometimes called white ants. They may resemble ants in size, but ants have a narrow waist and elbowed antennae while termites have a thick waist and antennae that resemble a string of beads.
Ecologically, termites play an important role in the environment by helping to break down and recycle dead wood and other plant tissues. They become pests when their appetite for wood and wood products extends to human homes, fence posts, building materials, cardboard, and other valuable products. In tropical and subtropical forests where termites are abundant, railroads must use expensive metal ties because wooden ones are quickly destroyed.
The Termite Colony.
Each termite lives in a nest or colony with hundreds, thousands, or even millions of its brothers and sisters. In fact, the termite colony is really a large, extended family. Within this family, various groups of individuals have different functional roles according to a “caste system”.
King – Fertile adult male
|Soldier Caste||Non-fertile males and females with special morphological adaptations for defense of the colony.|
|Worker Caste||Immature males and females (nymphs) – offspring of the king and queen, with potential to molt into replacement soldiers or reproductives if needed.|
The worker caste is the largest group. It consists entirely of immatures, both males and females. These soft-bodied, wingless individuals perform all of the hard labor in the colony: they clean, maintain, and repair the nest, gather food and water, care for the young, and construct new tunnels and galleries as the colony grows. These juveniles all have the genetic capacity to undergo additional molts and become soldiers or reproductives, but most will spend their entire lives as workers.
Members of the soldier caste are larger in size but fewer in number than the workers. They are also wingless, but they have large heads with powerful jaws. Their job is to guard the nest site and protect it from attacks by ants or other invaders. In some species the soldiers lack jaws but have a large gland in the head that shoots defensive chemicals through a nozzle at the front of the head. The soldiers are unable to care for themselves so they must be fed and groomed by the workers.
The reproductive caste always includes a king (male) and a queen (female) who are the parents of the termite family and founders of the colony. Some species also have a few supplemental reproductives who share the egg laying duties. These are the only adult insects in the colony. The queen lays large numbers of eggs which develop into more workers and soldiers as the family grows.
In every mature colony, there also develops an annual population of young winged reproductives that swarm from the parent nest for a short mating flight. After flight, the delicate wings break off, and the new king and queen set out to find another nest site and start a new colony. Large colonies with multiple reproductives may also split into two or more daughter colonies, a process known as “budding”.
The termite’s caste system is regulated by pheromones. The king and queen each produce special pheromones that circulate throughout the colony and inhibit workers of the same sex from molting into reproductive adults. A death in the royal family (or an increase in the size of the colony) results in a lower concentration of the corresponding pheromone and, subsequently, one or more workers will molt into replacement reproductives. Likewise, the concentration of sex-specific soldier pheromones regulate the numbers of male and female soldiers to fall within an optimal range based on colony size. Excess numbers of soldiers or reproductives may be killed and eaten by the workers.
Kinds of Termites.
About 2750 different species of termites are known. These can be divided into two groups: those that live entirely within wood, and more advanced species that tunnel and nest in the soil. In terms of their ecology and behavior, the most primitive species are similar to certain wood-dwelling cockroaches with whom they may share a common ancestor. These primitive species often have specialized habitat requirements, nesting only in rotten wood, damp wood, or dry wood. Their colonies are rather small and persist only as long as the food resource lasts. All wood-dwelling termites produce distinctive waste pellets which are often the first sign of an active infestation.
Subterranean termites construct underground nests and have the ability to tunnel through the soil to find new food resources. These colonies are often long-lived and may grow to include several million individuals. The subterranean termites that live in North America and Europe often invade wooden structures above the ground by building earthen tubes that serve as protective tunnels between the nest and their food source. These tubes are good evidence of a termite infestation.
In Africa and Australia, other subterranean species mix bits of soil with saliva to build nest mounds that are up to 20 feet (6 meters) tall. The inside of the mound is divided into numerous chambers and galleries. The king and queen live in a special cell deep inside the mound. The female’s abdomen grows in size until it is large enough to hold many thousands of eggs. The queen lays these eggs at the rate of several thousand a day. Worker termites carry the eggs away to specially constructed cells in the nest. There the workers care for the young as they hatch from the eggs.
Some of the mound-building termites cultivate underground fungus gardens. They collect dead plant material, mix it with saliva and their own waste products to create a paste, and inoculate this substance with the spores of a symbiotic fungus. The termites feed on special structures produced by the growing fungus.