Arthropoda: Social behavior of Termites | Zoology Optional Notes for UPSC PDF Download

Social Life in Termites: An Overview

• Termites, often referred to as "white ants," belong to the Class Insecta, Order Isoptera.
• They are widely distributed in tropical, subtropical, and temperate regions across the world.

• Termites are small, hemimetabolous insects with soft bodies.
• They are cellulose-eating, nocturnal, social, and polymorphic insects, characterized by having two pairs of similar wings.
• Termites are typically light-colored and should not be confused with ants, which are hard-bodied and dark-colored, with a constriction between the thorax and abdomen.

• Termites are ecologically important as they serve as efficient decomposers of dead wood and vegetable products.
• They contribute to agriculture by enriching the soil with their fecal matter and improving soil permeability to air and moisture, similar to the role of earthworms.
• However, they can also be significant pests, causing damage to wooden structures.

Colony Structure and Size

• Termites live together in large colonies or communities.
• There are over 1,700 species of termites, and colonies can range in size from a few hundred to as many as 7 million individuals of the same species.
• Colonies are matriarchal, initiated and maintained by a queen that can live for up to 50 years in some species.
• All colony members are the offspring of a single female, resulting in a similar genotype among all colony members.
• Colonies reach their maximum size in approximately 4 to 5 years.

Colony Structure and Polymorphism in Termites

• A termite colony consists of two main forms:
  1. Reproductive form or Fertile Caste
  2. Sterile form or Caste

Reproductive or Fertile Castes

• These are sexually mature males and females and serve as the ancestors of the termite community.
• They have two pairs of large, equal-sized wings that extend beyond the abdomen at rest.
• Their bodies are chitinized and dark brown, with well-developed compound eyes and a pair of ocelli.
• After maturity, they leave the nest, shed their wings, and mate.
• Each pair constitutes a dealated King and Queen or Primary Royal Pair.
• The queen can become significantly larger with a distended, bulbous abdomen and may produce up to 2,000 eggs per day. Royal couples can live for up to 50 years in some species.

Brachypterous Forms (Second Reproductive Caste)

• These are sexually mature males and females but appear nymphal in appearance.
• They have less chitinized bodies, are pale-colored, and possess short wing buds.
• Brachypterous individuals serve as substitutes or complemental kings or queens if the primary king or queen dies.
• Such queens produce fewer eggs.

Apterous Forms (Third Reproductive Caste)

• These rare forms are found in lower termites and encompass both males and females.
• They lack wings, have colorless cuticles, vestigial compound eyes, and lack ocelli.
• Known as Ergatoid Kings and Queens, multiple individuals of this caste may be present in a colony.

Sterile Forms or Castes

• Two types of wingless (apterous), sterile castes exist: workers and soldiers.

• Workers are the smallest in size, resembling nymphs with pale-colored, less chitinized bodies.
• They lack compound eyes and ocelli, and their heads are wide and point downwards.
• Worker duties include tending to eggs and young, foraging for food, cultivating fungi, nest construction, and feeding the queen and soldiers.
• Termites are destructive and pose a significant threat to crops and wooden structures as they are xylophagous, feeding on wood.
• They can digest cellulose with the help of symbiotic flagellates called Trichonympha.

• Soldiers are males and females without functional sex organs.
• They have large, dark chitinous heads and powerful mandibles, while their bodies are pale.
• Soldiers defend the colony, with mandibulate soldiers using their mandibles and nasute soldiers secreting a repellent fluid through the frontal rostrum.
• Mandibulate soldiers have no frontal rostrum, while nasute soldiers possess a median frontal rostrum on the head.
• Soldiers are less numerous in the colony compared to workers and require feeding by workers as they cannot feed themselves.

Termite Nests - Termitarium or Mound

• Worker termites are responsible for constructing elaborate nests, termed termitaria, which serve multiple purposes, including protection, food storage, and brood maintenance.
• Termite nests can range from simple cavities in soil or wood to extensive subterranean complexes or elaborate structures that rise above the ground in the form of mounds.
• These mounds can reach heights of up to 6 meters and are constructed from excavated mud, wood, excreta, and saliva. Their walls become as hard as rocks.
• The nests and termitaria feature a complex network of passages, chambers, and specialized cells for food storage and cultivating fungus gardens. Special chambers are dedicated to the royal couple.
• Termitaria are equipped with an advanced ventilation system, maintaining a constant temperature, canopies deflect rainwater, and various structural adaptations.

• Termites are renowned for their exceptional nest-building abilities.

Other Characteristics of Termites

• Various termite castes cooperate mutually and work together in an integrated manner within the colony.
• Parental care is well-developed in termites, with eggs and nymphs developing in fungal chambers or nurseries.
• The queen is cared for by workers who provide saliva and fungal hyphae.
• Workers tend to and feed nymphs with predigested fungus and vegetable matter, transferring symbiotic flagellates through trophallaxis.

• Some worker termites cultivate fungus gardens for the king, queen, and nymphs, which are located near the center of the nest.
• These fungus gardens are constructed from reddish-brown, spongy combs produced by workers from vegetable matter and excreta.
• Fungal hyphae grow on the comb, producing white patches.

• Termites communicate primarily through the secretion of chemicals called pheromones or ectohormones.
• Each colony develops its own characteristic odor, allowing instant recognition of intruders.
• Alarm pheromones are secreted upon detecting intruders, triggering soldiers to attack.
• Workers leave chemical trails to guide others to new sources of food.
• The proportion of different termite castes within the colony is regulated chemically.
• Sound also plays a role in communication, as soldiers and workers may create vibrations by banging their heads against tunnels, mobilizing the colony for defense.
• Mutual food exchange enhances member recognition within the colony.

Swarming

• Swarming in termites occurs for feeding, migration, mating, alleviating congestion, and distribution.
• Large numbers of males and females of various forms, such as macropterous and brachypterous, leave the nest in swarms after the onset of the rainy season.
• After a brief flight, they shed their wings and seek shelter to form new colonies.
• Copulation takes place in a nuptial chamber, and the pair becomes the originators of a new colony.
• After mating, the queen lays clusters of eggs, leading to the development of workers, soldiers, and other castes.
• Termite development is hemimetabolous, consisting of egg, nymph (larva), and adult stages.

Summary

• Termites build intricate nests for protection and other functions.
• They exhibit advanced social behaviors and communication through pheromones, sound, and food exchange.
• Swarming is a crucial part of termite life cycles, facilitating the formation of new colonies.