Social Organization and social behaviour of Insects

Social behavior refers to interactions between individuals of the same species, often providing mutual or individual benefits. In the case of insects, social behavior has evolved due to its advantages in survival and reproduction. By working together, individuals in insect societies enhance their ability to defend their colony, forage efficiently, and reproduce more successfully, thus increasing their evolutionary fitness.

Insects, such as ants, bees, wasps, and termites, demonstrate some of the most complex forms of social organization in the animal kingdom, known as eusociality. Eusocial insects exhibit three primary characteristics: cooperative care of offspring, division of labor, and overlapping generations within a colony. This level of social organization allows them to form highly structured communities where individuals have specific roles, such as workers, soldiers, or reproductive members, enhancing the colony’s efficiency and survival.

The division of labor is one of the most fascinating aspects of insect social behavior. For example, worker ants are responsible for foraging, maintaining the nest, and caring for the young, while the queen’s sole function is reproduction. This separation of tasks ensures that all essential functions within the colony are covered, optimizing the survival of the entire group.

Furthermore, social insects often communicate through chemical signals, known as pheromones, which help coordinate activities like foraging, defense, and reproduction. In ants, for instance, pheromones are used to mark trails leading to food sources, allowing other colony members to follow the path efficiently. This communication system enables large colonies to function as a unified entity, with individual insects acting for the benefit of the group rather than for personal gain.

The evolution of social behavior in insects is a remarkable example of how cooperation can drive the success of a species. By forming complex societies with specialized roles and sophisticated communication systems, these insects have thrived in a variety of environments. Therefore, understanding the social behavior of insects not only provides insights into their success but also offers broader lessons on the advantages of cooperation in the natural world.

Characteristics of social insects

Social insects exhibit distinct characteristics that enable them to form complex, cooperative societies. These characteristics not only ensure the survival of individuals but also the efficiency and continuity of their colonies. Below are the key characteristics of social insects:

• Large population: Colonies of social insects harbor large populations. For example, honey bee hives can house 20,000 to 80,000 worker bees, while ant colonies may contain up to 600,000 individuals. Termite nests can reach several million termites. Multiple generations coexist within these colonies, which are typically matriarchal, meaning most members are descendants of a single female.
• Elaborate nests: Social insects construct intricate nests to protect their young and store food. These nests are often perennial and are initiated by the reproductive caste but maintained by the workers. For instance, honey bee hives feature hexagonal wax cells, while termite nests (termitaria) may contain fungal gardens for cultivating fungi. The structure of these nests often includes brood chambers, royal chambers for reproductive members, and storage cells.
• Caste system: Colonies are divided into distinct castes, with each caste performing a specialized role. The primary division is between reproductive members (queens and kings) and sterile members (workers and soldiers). In some species, the queen’s sole function is to lay eggs, while soldiers protect the colony. In termites, soldiers can be mandibulate, equipped with strong jaws, or nasute, ejecting chemicals for defense. Ants have the most elaborate caste system, with caste differentiation influenced by genetic, environmental, and nutritional factors.
• Protective devices: Social insects have evolved various mechanisms for colony defense. Worker bees possess stingers, while termite soldiers are tasked with defending the colony, some with large mandibles and others capable of chemical warfare via nasute projections. These adaptations serve to repel predators and protect the colony from threats.
• Cohesiveness of the colony: The success of a social insect colony depends on cooperation. Colony members are interdependent, with each caste working toward the collective benefit. This cooperation is facilitated by chemical and physiological mechanisms that bind members together, ensuring smooth operation and unity.
• Parental care: Parental care in social insects is instinctual, with workers providing food, maintaining hive temperature, and tending to the young and the queen. Workers also handle tasks like cleaning, repairing the nest, and provisioning food. This care ensures the colony’s reproductive members and developing young are well-nourished and protected.
• Progressive provisioning of food: Social insects provide continuous feeding to developing young until they reach adulthood, unlike species that rely on mass provisioning. Workers typically provide for the immature stages, with some ants even farming aphids for honeydew or gathering and storing seeds for winter.
• Trophallaxis: Trophallaxis, or mouth-to-mouth feeding, is a critical behavior in many social insects. Workers feed the young and reproductive members of the colony. In termites, this feeding behavior is important for caste determination, as ectohormones are passed during feeding, influencing the development of nymphs.
• Swarming: Swarming involves the movement of large groups of individuals for feeding, migration, or mating. It reduces overcrowding and allows colonies to escape adverse conditions. In honey bees, swarming is also a mechanism for colony multiplication, with the queen leading a group of workers to establish a new hive.
• Communication: Social insects rely on tactile, chemical, visual, and auditory signals for communication. Pheromones are used by ants and termites to mark foraging trails, while the honey bee queen secretes substances to inhibit the reproductive abilities of workers. Honey bees also perform dances to communicate the location of food sources.

Benefits of social behavior

Social behavior offers numerous advantages to species that engage in it. These benefits often contribute to enhanced survival and reproductive success, providing a strong evolutionary advantage. Below are the key benefits of social behavior:

• Increased success in finding food: Many animals that work in groups have a higher chance of locating food. When multiple individuals cooperate, the likelihood that at least one will discover a food source increases, benefiting the entire group.
• Enhanced foraging efficiency: When animals search for food in groups, they can cover a larger area more efficiently. This collective effort improves their chances of encountering food, especially in environments where resources may be scarce or difficult to locate.
• Improved prey capture: In some species, group hunting increases the chances of successfully capturing prey. By working together, predators can take down larger or faster prey than they could individually. For instance, lions hunt wildebeests and wolves hunt moose more effectively when they cooperate as a pack.
• Coordinated hunting techniques: Some animals, like dolphins, use social behavior to create strategic hunting methods. Dolphins will encircle a school of fish, taking turns darting into the center to catch the trapped prey, ensuring a higher success rate for each individual.
• Group hunting of large prey: Carnivorous animals, such as wolves and lions, often band together to hunt large prey. By combining their efforts, they can overpower animals much larger than themselves, increasing their chances of a successful kill and ensuring the group is well-fed.
• Protection from predators: Living in social groups provides protection. Many animals form groups to reduce the risk of predation, as it is more challenging for predators to target an individual in a large group. The collective vigilance of the group increases the chances of spotting danger early and escaping.
• Facilitated travel: For some species, social behavior makes traveling more efficient. Groups can navigate large distances more easily, whether migrating to new habitats or moving in search of food, as they benefit from group coordination and protection during their journey.

Characteristics of social behavior

Social behavior in animals is defined by their interactions within a group, leading to various adaptive advantages. Social insects, in particular, exhibit well-developed characteristics of social behavior, which contribute to the structure and functioning of their colonies. Here are the key characteristics of social behavior in insects:

• Colony:
  • Social insects live in organized colonies, which may house tens of thousands to millions of individuals, such as 10,000-50,000 honey bees, 600,000 ants, and millions of termites.
  • All members of a colony are typically the offspring of a single female, meaning they share a common genotype, which enhances colony cohesion.
• Nest:
  • Social insects build complex nests for protection, food storage, and rearing their young.
  • Honey bees construct wax combs made up of hexagonal cells, often found in trees or man-made structures.
  • Ants build tunnel-like nests from soil or wood, with multiple exits for defense and movement.
• Caste System:
  • Division of labor in social insects leads to a caste system, where members are morphologically and behaviorally specialized for specific roles.
  • The primary castes include reproductive (queen and king) and sterile (workers and soldiers). Workers, in many species like honey bees and wasps, are sterile females, whereas in termites and ants, both males and females can serve as workers.
  • Factors determining caste include genetics and nutrition in bees, wasps, and ants, and external influences such as ectohormones in termites.
• Parental Care:
  • Instinctive behaviors, including feeding, cleaning, and egg-laying, define parental care in social insects. Workers are responsible for maintaining these tasks to ensure the colony’s well-being.
• Progressive Provisioning of Food:
  • Social insects provide continuous care to their young throughout development, feeding them until they metamorphose into adults.
  • Some ants nurture aphids in their nests, feeding on the honeydew they produce, while protecting them from predators. Fungus-growing ants cultivate fungi in specialized chambers and provide organic matter to nourish these fungal crops.
• Trophallaxis:
  • The exchange of food among colony members is known as trophallaxis. This mutual feeding strengthens social bonds and helps nourish younger or reproductive members.
  • In termites, trophallaxis plays a significant role in caste determination. Hormones exchanged during feeding regulate the development of nymphs into specific castes, such as workers or soldiers.
• Swarming:
  • When colonies grow too large, a portion of the population swarms, relocating to a new area. Swarming is critical for reproduction, migration, and colony distribution.
  • In certain species, such as honey bees, a nuptial flight occurs, where queens and males leave the colony for mating.
• Protective Devices:
  • Social insects have evolved various protective mechanisms. Honey bees and wasps possess venomous stings, while ants and termites have developed strong mandibles for defense.
• Communication:
  • Social insects communicate using chemical signals (pheromones), tactile cues, visual displays, and sounds.
  • For example, ants leave chemical trails to guide others, while honey bees perform specific dances to convey information about food sources, a behavior famously studied by Von Frisch.

Social organization in honey bee

Caste System

The caste system in social insects, such as honey bees, is a highly structured hierarchy, where different types of individuals are specialized for specific roles, all contributing to the functioning and survival of the colony. Each caste exhibits distinct morphological and behavioral traits, ensuring the efficient division of labor.

• Queen:
  • The queen is the reproductive center of the colony, being the only fertile female and the largest individual.
  • She has a long, tapered abdomen, small brain, and underdeveloped salivary glands. Unlike other members, the queen cannot produce honey, wax, or collect pollen.
  • Developing from fertilized eggs, the queen is raised in a specialized larger chamber known as the “queen cell” and fed royal jelly throughout her larval stage.
  • The queen’s primary function is reproduction. She is strictly monogamous, mating only once in her lifetime. Post-mating, her abdomen enlarges to accommodate her ovaries, a phenomenon seen across other social insects, referred to as physogastry.
  • The queen lays both fertilized and unfertilized eggs, producing workers (from fertilized eggs) and drones (from unfertilized eggs).
• Drones:
  • Drones are the male members of the colony, produced parthenogenetically from unfertilized eggs.
  • They possess large wings that extend beyond the tip of their abdomen and develop in larger, hexagonal cells within the hive.
  • Their sole function is reproduction. They participate in the nuptial flight, during which they mate with a queen. After mating, drones either die or are expelled from the colony by workers.
• Workers:
  • Workers are the smallest and most numerous individuals in the colony. They are sterile females, hatched from fertilized eggs, and their bodies are highly specialized for a wide array of functions.
  • Covered densely in hair, workers have mouthparts adapted for biting and lapping, ideal for foraging. Their spoon-shaped mandibles are used for molding wax, while their legs are adapted for pollen collection and storage.
  • The forelegs contain an eye brush and antenna cleaner, the mid-legs possess a pollen spur, and the hind legs have a pollen basket. These adaptations play a crucial role in gathering and transporting pollen back to the hive.
  • The wax glands, located on the ventral surface of the workers’ abdominal segments, produce the wax used for constructing and maintaining the hive.
  • Workers’ salivary glands are well-developed and are responsible for producing royal jelly, which is used to feed larvae in the initial stages of their development.
  • Their wings feature hamuli, small hooklets on the anterior margin of the hindwings that fit into sockets on the posterior margin of the forewings, ensuring efficient flight.
  • The workers’ ovipositors are modified into a sting apparatus, which they use in defense. The poison delivered through their sting is primarily acidic.
  • Workers undertake nearly all colony activities except reproduction. These tasks include feeding and caring for the larvae, attending to the queen, constructing and maintaining the hive, foraging for food, and defending the colony.

Beehive

A beehive is a complex and meticulously organized structure, created by honey bees to store food, rear young, and ensure the colony’s survival. Built in a hanging position from trees, buildings, or rocks, the hive consists of thin walls made of beeswax, forming two layers of hexagonal chambers known as honeycombs. These chambers serve distinct purposes within the hive, facilitating the storage of food and the development of new bees.

• Bee Wax and Construction:
  • Beeswax, secreted from specialized wax glands located in the abdomen of worker bees, is the primary material used to construct the hive.
  • Workers chew the wax and mix it with secretions from their cephalic glands, transforming it into a pliable substance to build honeycombs.
  • Additionally, bees use propolis, a resinous mixture made from plant materials, to waterproof the hive and repair any damages. The resins and gums collected from plants are used for sealing and reinforcing the hive structure.
• Storage Cells:
  • Storage cells are located at the margins and top of the honeycomb, serving as repositories for honey and pollen. These cells ensure that the colony has food reserves, especially during times when foraging is not possible.
• Queen Cells:
  • Queen cells are specialized, peanut-like chambers designed for the development of the queen bee. Larger than other cells, these are built away from the regular worker and drone cells.
  • The queen larvae are fed royal jelly by the worker bees. Once the queen pupates, the cell is sealed with beeswax by the workers. There are three types of queen cells, each serving a specific purpose in the hive’s reproductive process:
    1. Swarm Cells: These are formed when the colony becomes overcrowded. A second queen is raised, and the original queen departs with part of the colony to form a new hive. Swarm cells are typically lumpier and hang vertically.
    2. Supersedure Cells: These cells are created when the existing queen is injured, aging, or otherwise unfit to continue leading the colony. A new queen is raised by feeding young larvae royal jelly.
    3. Emergency Cells: Built when the queen dies unexpectedly, these cells are formed by converting existing brood cells into supersedure cells, ensuring the rapid development of a new queen. These cells have a distinct shape, being partly horizontal and partly vertical with a right-angle bend.
• Drone Cells:
  • Drone cells are larger than worker cells and are clustered at the bottom of the hive. Their dome-shaped design features a higher and rounded cap. These cells house drones, the male bees, and make up about 30% of the total cells in the hive, though the number may vary based on factors like season and colony genetics.
• Worker Cells:
  • Worker cells, which are smaller and slightly domed, are the most numerous in the hive. Located primarily in the center of the honeycomb, they serve a dual purpose. In the lower part of the honeycomb, worker cells are used to rear worker bees, while in the upper sections, they store honey and pollen. The structure and organization of worker cells are critical for maintaining the colony’s productivity and food supply.

Social organisation in termites

Termites, commonly referred to as white ants, are fascinating insects that exhibit complex social organization. They belong to the class Insecta and order Isoptera, and they are predominantly found in tropical, subtropical, and temperate regions worldwide. Known for their soft bodies and hemimetabolous development, termites are primarily cellulose-eating, nocturnal creatures that thrive in large colonies. These colonies can comprise hundreds of thousands, and in some cases, millions of individuals, all of which stem from a single reproductive female, the queen. Understanding the social structure of termites provides insight into their ecological role as decomposers and their impact as pests.

• Colony Structure:
  • Termite colonies are matriarchal and can include over 1,700 species. A colony’s population typically stabilizes and reaches its maximum size within four to five years. The queen can live for up to 50 years and may lay around 2,000 eggs per day, significantly contributing to the colony’s growth.
  • All members of a colony share a similar genotype due to their descent from a single queen, which reinforces the importance of genetic consistency in colony functioning.
• Caste System:
  • The termite colony consists of two main forms: reproductive forms (fertile castes) and sterile forms (caste). Each caste has specific roles essential for colony survival and efficiency.

1. Reproductive Forms (Fertile Castes):
   • Macropterous Forms (Winged Forms):
     • These are the sexually mature males and females, often referred to as the primary reproductive caste.
     • They possess two pairs of large, equal-sized wings and are capable of flight until they shed their wings after mating.
     • The body is chitinized and dark brown, with well-developed compound eyes and larger sex organs compared to other castes.
     • Upon mating, they seek a location to establish a new colony, becoming the king and queen of their new nest.
   • Brachypterous Forms (Short-Winged Forms):
     • These individuals are also sexually mature but resemble nymphs and possess only short wing buds.
     • They remain within the nest and can replace the primary king or queen if necessary, becoming polygamous.
     • Their egg production is lower than that of macropterous forms.
   • Apterous Forms (Wingless Forms):
     • Rarely found and primarily located in lower termites, these forms appear similar to nymphs and lack wings.
     • They are often referred to as Ergatoid Kings and Queens and may exist in several numbers within a colony.
2. Sterile Forms (Caste):
   • Sterile Workers:
     • These wingless individuals are crucial to the colony’s daily operations. They are smaller in size, pale in color, and have rudimentary body structures.
     • With a colony population that can reach up to 200,000, workers are responsible for nurturing eggs and nymphs, foraging for food, and maintaining the nest.
     • They are also essential for cultivating fungal gardens, which serve as a primary food source, and are capable of digesting cellulose with the help of symbiotic flagellates, such as Trichonympha.
   • Sterile Soldiers:
     • Characterized by large, dark heads and formidable mandibles, soldier termites play a vital role in colony defense.
     • They require sustenance from workers and are equipped with either large mandibles or specialized frontal rostrums to exude defensive fluids.

• Nest Construction (Termitarium):
  • Worker termites are responsible for building elaborate nests, known as termitaria, which can vary from simple soil cavities to towering mounds up to six meters high.
  • These nests are made from a combination of mud, wood, and excrement, mixed with saliva, and are characterized by their hard, rock-like walls.
  • Inside, the termitaria contain a complex network of passages and chambers designed for food storage, cultivation of fungi, and rearing of young. They are equipped with ventilation systems to regulate temperature and protect against rain.
• Parental Care and Food Exchange:
  • Termites exhibit notable parental care, with workers tending to the eggs and nymphs in designated fungal chambers.
  • Trophallaxis, or the mouth-to-mouth transfer of food, is crucial in this process, allowing the sharing of nutrients and symbiotic microorganisms essential for digestion.
  • The cooperative behaviors among castes facilitate the transfer of food and the exchange of pheromones, regulating caste development and colony dynamics.
• Communication:
  • Termites utilize chemical signals known as pheromones to communicate within the colony. Each colony possesses a unique odor that helps in recognition of intruders and the organization of colony activities.
  • Alarm pheromones trigger defensive behaviors from soldiers when the colony is threatened, while food sources are indicated through pheromone trails laid by foraging workers.
  • In addition to chemical communication, termites also produce vibrations by banging their heads against tunnel walls, which serves as an alert mechanism for mobilizing the colony.

Social system in primates

Social systems among primates exhibit a remarkable complexity that reflects their evolutionary adaptations and ecological demands. These systems are characterized by various forms of social organization that facilitate survival, reproduction, and social learning. The sociality observed in primates can be attributed to several factors, including increased brain size, the development of dexterous hands, reliance on visual communication, and adaptability to diverse habitats.

• Enlargement of Brain: The larger brain size in primates supports complex social interactions, allowing for advanced problem-solving and social cognition.
• Development of Grasping Hands: This adaptation enables primates to manipulate their environment effectively, facilitating various social behaviors, including grooming and food sharing.
• Vision Reliance: Primates’ acute visual capabilities aid in communication and the recognition of social cues, which are crucial for maintaining group dynamics.
• Diverse Habitats: Primates inhabit both arboreal and terrestrial environments, leading to varied social structures based on environmental factors.

The social behaviors in primates can be classified into six primary types, each with unique characteristics and implications for their social organization.

1. Solitary Type:
   • Examples: Orangutans, aye-ayes, and lorises.
   • Characteristics: These primates live predominantly in isolation, occupying a defined home range. For instance, orangutans associate primarily for mating purposes, with offspring relying on maternal care.
   • Behavioral Aspects: They follow seasonal fruiting patterns and remain largely arboreal.
2. Monogamous Type:
   • Examples: Gibbons, tree shrews, lemurs, and marmosets.
   • Characteristics: Monogamous arrangements are rare among primates, yet gibbons exemplify this through lifelong pair bonds. These groups usually consist of an adult male, female, and their offspring, with notable equal participation in activities and parental investment.
   • Behavioral Aspects: Gibbons engage in elaborate vocalizations to defend their territory, and marmosets often have twins, with males playing a significant role in infant care.
3. Single Male Groups (Unimale Bisexual Groups):
   • Examples: Patas monkeys, hanuman langurs, and red howler monkeys.
   • Characteristics: These groups typically consist of one dominant male and multiple females and young. The male, often referred to as the overlord, directs group activities and territorial defense.
   • Behavioral Aspects: The dominance hierarchy is clear, with males exhibiting significant physical differences compared to females, and male parental investment is minimal.
4. Aggregate Single Male Groups:
   • Examples: Baboons.
   • Characteristics: In these social structures, several females are bonded to a single male, forming harem-like groups. Such groups may come together to form larger troops for foraging and sleeping.
   • Behavioral Aspects: Baboons exhibit flexible group dynamics, often separating into smaller units during foraging and regrouping for social interactions.
5. Multimale Bisexual Groups:
   • Examples: Rhesus monkeys, gorillas, and spider monkeys.
   • Characteristics: These groups feature multiple adult males and females, with social hierarchies influencing group interactions. In gorillas, a clear dominance hierarchy exists among males, with the alpha male leading the group.
   • Behavioral Aspects: Rhesus monkeys demonstrate a complex social structure where female dominance is often linked to the status of their bonded males. Dominance behaviors are visibly marked by the males’ body language.
6. Diffuse Social Parties:
   • Examples: Chimpanzees.
   • Characteristics: Chimpanzees exhibit a fluid social structure, where group sizes vary based on food availability. Males defend territory and organize into smaller foraging parties when necessary.
   • Behavioral Aspects: Communication within these groups relies heavily on vocalizations and body language, reflecting a sophisticated social awareness.

Primate social systems demonstrate several unique features:

• Close Associations: Primates form social bonds within territorial limits, facilitating resource sharing and protection.
• Information Sharing: Group members continuously exchange vital information regarding food sources, threats, and social dynamics.
• Group Size Variation: Social group sizes can range from pairs to hundreds, adapting to environmental conditions.
• Rank Relations: Social hierarchies influence interactions, with clear distinctions in dominance based on age, sex, and individual personality traits.
• Communication: Social organization emphasizes the importance of communication through sounds and gestures, allowing members to respond to social cues effectively.
• Division of Labor: Specific roles are often assigned based on individual status, aiding in group cohesion and efficiency during foraging, parenting, and defense.

The advantages of such social organization include:

• Permanent Structures: Stable social hierarchies facilitate group coherence.
• Enhanced Communication: Clear communication channels improve group cohesion and reduce misunderstandings.
• Specialization: Role differentiation enables efficient resource utilization and conflict resolution.
• Cohesion: Strong bonds among members enhance collective defense mechanisms against threats.