Social Insects

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  • Topic: Ant, Insect, Eusociality
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  • Published : December 9, 2012
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Social Insects

“The little things that run the world”- E.O. Wilson

Social Insects
I. Levels of sociality II. Castes and Polyethism III. Social insect examples IV. Ecological success

• A group of individuals that belong to the same species and are organized in a cooperative manner.


• Non-social grouping of individuals

Monarch butterflies aggregating

Levels of Sociality
• • • • • Solitary Subsocial Parasocial Eusocial Presocial

Classification system for presocial and eusocial insects
Common nest Cooperative site brood care Reproductive castes Generational gap Solitary Subsocial or communal No Yes No No No No No No

Quasisocial Semisocial Eusocial

Yes Yes Yes

Yes Yes Yes

No Yes Yes

No No Yes

• Interactions among individuals limited to sexual behavior and competiton • Adult-to-offspring relationship limited to oviposition • EXAMPLES: phasmids, solitary bees

• Adults protect/and or feed the young after hatching, but parents take off or die prior to maturity of offspring (limited parental care) • Some provide food (progressive provisioning) Female shield bug protects her brood from a predatory spider

• Interactions among adults of the same generation • Includes communal, quasi-social, and semisocial behavior – Communal (aggregate to build nests together, but construction & provisions is done individually) – Quasi-social (while making provisions for own eggs, individuals share their provisions) – Semisocial (females are mated and lay eggs as queens)

Semi-social: Polistes (paper) wasps

• Any social behavior beyond sexual behavior, yet short of eusocial behavior

Myschocyattarus spp. Vespidae Paper wasps from Indonesia

“true sociality” requires: 1) Cooperative brood care 2) Reproductive division of labor 3) At least 2 generations overlap (kids aid parents in colony work)

Honey bees on brood comb

Eusocial Insect Groups
1) ISOPTERA: termites 2) HYMENOPTERA: ants, bees, and wasps 3) OTHERS: one species of thrips, some aphids, ambrosia beetle

Isoptera: Termites
• All termites are eusocial • Diet: cellulose • Male and female workers and soldiers • The “king” is permanent attendant of the “queen”

• 1/3 of animal biomass • Key herbivores in the tropics • Important terrestrial predators • Move soil in the tropics

• Scavengers • Farmers (Acromyrmex or Atta) • Honeydew: “Aphid pastoralists” • Keep slaves • Seed harvesters • Intimate interspecific symbiosis • “depletes”


• solitary to eusocial • Bumblebees: thermoregulation experts • Stingless bees: (Melipona or Trigona)


• Almost all social except Sphecidae • Vespula: hornets and yellow jackets • Polistes: paper wasps • Polybiine: tribe with multiple queens • Generally less elaborate castes and communication systems than bees and ants

Castes and Polyethism
• Caste: a specialized segment of the population of social insects. • Polyethism: Behavioral differences among castes (division of labor) • Polymorphism: caste members are radically different in appearance

Termite Castes

Honeybee Castes

The Drone Bee
• • • • These are the males Sole purpose is to mate with the queen They have no stingers If colony is low on food, they usually are kicked out of the hive.

Worker Bee (Aculeate)
• • • • • • • • Smallest bees in colony They are undeveloped females 50,000-60,000 per colony Life span of 28 to 35 days Feed the queen and the larvae Guard the hive Collect nectar to make honey They produce the wax comb

Reproductive Castes
• Bees: males don’t work or leave hive except for mating (drone) • Termites: males are equal partner in colony maintenance

The Queen Bee
• Lays all the eggs and regulates sex of offspring (parthenogenesis). – Unfertilized eggs -> males – Fertilized eggs -> females

• All members of the hive are...
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