Social Insects Overview

Social Insects

• Social insects challenge the mind with their sheer number and variety.
• There are more ant species in a square kilometer of Brazilian forest than primate species worldwide.
• A single driver ant colony has more workers than all African lions and elephants combined.

What is a Social Insect?

• Social insects, also known as eusocial insects, include ants, termites, and highly organized bees and wasps.
• They are distinguished by three key traits:
  • Cooperative care of young by individuals of the same species
  • Reproductive division of labor, with some individuals working for the reproductive members of the colony
  • Overlap of at least two generations in the colony where offspring help the parents

Degrees of Sociality

• Presocial: Social behavior that is developed beyond sexual behavior but falls short of eusociality.
• Parasocila sequence includes:
  • Solitary
  • Communal
  • Quasisocial
  • Semisocial
  • Eusocial
• Subsocial sequence includes:
  • Solitary
  • Primitively subsocial
  • Intermediate subsocial I
  • Intermediate subsocial II
  • Eusocial
• In the parasocial sequence adults from the same generation cooperate in varying degrees.
• At the lowest level (communal) there is cooperation in building nests but separate brood care.

Organization of Insect Societies

• Once eusociality is achieved, organization advances through:
  • Increased numbers and specialization of worker castes
  • Enhanced communication codes for colony coordination

Social Insects: Wasps

• Wasps belong to the order Hymenoptera, suborder Apocrita.
• Some wasps are stinging insects.
• Wasps are distinguished from ants and bees.
• Wasps are predatory or parasitic.
• Have stingers, but they lack barbs, so they can be easily removed from victims.
• They have a narrow petiole (waist) that attaches the abdomen to the thorax.
• Wasps are categorized into solitary and social wasps.
  • Solitary wasps live alone.
  • Social wasps live in colonies.
• Social wasps belong to the Vespidae family.
• The social wasps are confined to about 1,000 species and include hornets and yellowjackets.

Social Insects: Wasps - Additional Details

• In social wasps within Vespidae, there is a caste system:
  • Queens (fertilized females): Start the colony by laying eggs.
  • Workers (sterile females): Care for eggs, larvae, build the nest, acquire food, and defend the nest.
• They build a paper-like nest out of chewed plant material mixed with saliva.
• Nest locations vary depending on the species,
  • cavities in the ground
  • tree trunks
  • eaves of buildings.
• Many species have an annual life cycle in which the only overwintering individuals are queens.

Social Insects: Ants

• Ants are the dominant social insects, geographically widespread, and numerically abundant.
• Their success is attributed to:
  • Evolution of wingless workers enabling deep foraging into soil and crevices around 100 million years ago.
  • Predatory habits of primitive ant species
  • Ability to nest in soil and leaf mold, providing rich energy resources.
• Metapleural glands present in ants produce acid that inhibits the growth of microorganisms, which contributes to colony hygiene.

Social Insects: Ants - Colony Structure

• Colonies range in size from small to large.
• Colonies consist of a queen (egg-laying), many workers (sterile females), and males that emerge from the nest, and mate, only for a short period, then die.
• Workers perform various tasks.
• Young workers commonly tend brood (eggs, larvae, pupae).
• As the workers age, their tasks often shift from brood care to nest construction, excavation, and eventually foraging.

Social Insects: Ants - Additional Details

• Ants exhibit varying worker sizes (monomorphic or polymorphic), where workers are all the same size or different sizes respectively.
• Two different sizes (dimorphic) or a wide range of sizes (polymorphic).
• Males and females have similar or smaller sizes with similar or smaller heads
• Differences can be seen in bodies, ocelli, and mandibles.

Explore the fascinating world of social insects, including ants, termites, and bees. This quiz delves into their unique characteristics, degrees of sociality, and the impressive numbers that define their colonies. Test your knowledge on these remarkable creatures and their complex behaviors.