Social Insects
Live together in organised groups or colonies.
Each individual contributes towards welfare of the entire group.
Large populations — complex social aggregate called a colony.
All members in a colony are offspring of a single female and have similar genotypes.
Generally hostile to members of other colonies and use chemical cues to identify members of own colony.
Elaborate nests for storage of food and maintenance of broods.
Polymorphism:
-Division of labour into different castes, which are morphologically distinct. Each caste has its own distinct role to play in the colony. e.g. Queen, Workers and Drones.
-The castes in an insect colony are subordinated to the life of the community. They are bound by physiological and chemical mechanisms.
-Castes which differ in structure and physiology cannot live independently.
-Success is measured in terms of the colony and not the individual.
Parental Care: Entire colony cares for the brood as a whole. Provisioning of food, cleaning and feeding the young, removal of debris, putting eggs in proper chambers etc.
Provisioning of Food:
-Mass Provision: (Potter Wasps) — Lay their eggs with sufficient mass of food for complete development of the larva.
-Progressive Provision: (Bees, Ants, Termites) — Feed their young on a day to day basis until they metamorphose into adults.
Trophallaxis: Exchange of food between insects (Adult-Young or Adult-Adult). Ectohormones containing inhibitory substances are passed on to Nymphs by reproductive classes and workers, which prevents them from developing into the same caste.
Swarming: Occurs for feeding, migration and mating. Mating between queen and mates during Swarming is called nuptial flight.
Queen Substance on the body of the queen inhibits workers from becoming queen when they come in contact with this substance.
Protective Devices: Stings in Bees, Jaws in ants. Guard castes protect the nests and attack the intruders.
Polymorphism
Genetics and Nutrition forms the basis of polymorphism in bees.
-Unfertilised eggs become Drones (males).
-Fertilised eggs fed royal jelly form Queens.
-Fertilised eggs fed beeswax form Workers.
Isoptera — Termites:
-Determination of castes is by extrinsic factors.
-Reproductive forms and soldiers secrete ectohormones containing inhibitory substances.
-When fed to Nymphs, these substances prevent them from developing into like forms.
Honey Bee
| Organised social insects. Species in India: Apis dorsata, Apis mellifera, Apis cerana, Apis indica Apis indica is the most popular species in bee keeping, as they can be easily domesticated. Phylum: Arthorpoda > Class: Insecta > Order: Hymenoptera > Family: Apidae > Genus: Apis Polymorphism and division of labour. | Life Cycle: Queen bee lays eggs in a wax cell. Worker bees feed hatched larva. Larva reaches full growth. Workers seal the cell with wax. Larva spins cocoon and changes into a pupa. Adult bee leaves the cell. |
Queen lays eggs
-Fertilised
Hatch — Royal jelly for few days — Honey and pre digested pollen — Pupa — Worker
Hatch — Royal jelly for few days — Royal Jelly continued feeding — Pupa — Queen
-Unfertilised
Hatch — Royal jelly for few days — Honey and pre digested pollen — Pupa — Drone (Haploid
Male)
| Worker Bees | Drones | Queen |
| Sterile. Clean the hive and feed the larvae (0-10 days). Makes honey out of nectar brought by foragers (16-20 days). Leaves the hive and spends rest of life as forager (after 20 days). When old queen dies/becomes weak, workers construct superseder queen cells. Physical features Long proboscis for sucking nectar. Strong wings for fanning. Pollen baskets. Sting. Wax Gland. | Genetically haploid males. Weak mouthparts — cannot forage. Fertilise the queen during nuptial flight. | Reared in specialised large queen cells, which are specially constructed for the queen larva, and have a vertical orientation. After nuptial flight, queen stores sperms in small sac like organs called spermatheca. |
Workers secrete pheromones from Nasonov gland, which are inside the tip of the abdomen. This helps workers identify members of their colony.
Pheromones produced by the queen bind the colony together.
When a queen takes nuptial flight, her pheromones attract the drones. Drones copulate during the flight, and die after transferring the sperm.
Queen Substance: Licked by workers from the queen’s body. Inhibits the ovaries of workers and makes them sterile.
Mandibular glands of workers produce an alarm pheromone.
Workers leave the sting in the body of the victim, which produces a sting door, attracting other bees to the area for stinging.
Supersedure: When egg laying capacity of old queen is lost or it suddenly dies, a new and young queen takes her place.
Absconding: Migration of complete colony from one place to another due to unfavourable conditions, such as destruction of comb or scarcity of nectar producing flowers.
Swarming: Process of leaving of the colony by the queen. Queen leaves with some of the old drones and workers and establishes a new hive at another place.
Termites
Less advanced form of social life compared to ants.
Three classes of individuals, and each class includes both sexes.
Cate system of the colony is maintained by social hormone (pheromone), secreted by reproductive castes.
| Fertile Castes | Sterile Castes |
| Large Winged Forms: King and Queen, Ocelli are present, Duty of Queen is to lay eggs. Short Winged Forms: Supplementary kings and queens. Wings are short, pad like and vestigial. Ocelli may be present or not. Wingless Forms: Wings are absent, Ocelli are absent. | Wingless, Eye-less and Colourless, Sex Organs are rudimentary, Incapable of reproduction. Workers: Dimorphic, construct and repair the nest, distribute food, take care of young and eggs. Can metamorphose into winged reproductive castes. Soldiers: larger than workers. Defend the colony. Have mandibles for attacking. Nasutes: Large head prolonged into a rostrum. Secrete defensive substances. |
Feeding
Feed on living as well as dead plant material.
Digest cellulose with help of symbiotic protozoa.
Swarming
In rainy season, the king and queen are produced in large numbers.
They leave the termitarium through holes made by the workers and fly away to new sites. (Swarming or Dispersal flight).
Founding of New Colonies
At a new site, king and queen mate, shed wings, dig out a burrow and start a new colony.
Queen lays eggs and these eggs hatch into workers.
When her fertility lessens, her feeding is suspended and she dies of starvation.