C1139 Social Insects. The Society. Lecture 4
The society: life cycle and kin structure
Aims
1. To provide information on colony life cycles and kin structure.
Objectives
1. To learn some of the diversity of colony life cycles in the Hymenoptera (e.g. how colonies are founded;
stages in the colony life cycle: founding, growth/ergonomic, reproductive,
queenlessness/decline/death), including specific examples.
2. To learn some of the diversity in the kin structure of colonies caused by variation in the number of queens
and the number of males to which queens are mated, including specific examples.
Big Picture
The previous lecture looked at the individuals within a society. The individuals are the building blocks of an
insect society. In this lecture we will consider the colony as a whole. A colony of eusocial insects is not
some random collection of conspecifics. Different taxa typically have well defined colony characteristics,
such as the way that a new colony is founded, the life cycle of the colony, the size it reaches, and the type of
nest it builds. We will focus on two key properties: colony life cycles and kin structure.
Colony founding by a single queen
Most multi-cellular organisms start life as a fertilized egg. Something analogous is also common in social
insects. The most common way for a hymenopteran colony to be founded is by a single inseminated queen.
This is sometimes called “haplometrosis”, but a more user-friendly term is “single-queen founded”. This is
the way that colonies are founded in most ants, Vespinae wasps, bumble bees (Bombus spp), and Halictidae
sweat bees. In termites, the most common method is by a mated pair. After a nuptial flight, termite kings and
queens rapidly pair up and look for somewhere to establish a nest.
In most ants, the newly-mated queen finds somewhere suitable to nest and snaps off her wings. She
rears the first batch of larvae using her body reserves (fat, flight muscles) which are converted into eggs or
oral secretions to feed the larvae. The first larvae often give rise to small workers known as minims or
nanitics. They then take over the work and forage. The queen herself does not forage. This is known as
claustral founding. (In some ants the queen does forage.) In bees and wasps the queen forages for food, and
in wasps for building materials as well.
Colony founding by multiple queens
This is called “pleometrosis” or “multiple-queen founding”. It can also be referred to as a "foundress
association" or "primary polygyny".
In many ants two or more unrelated ant queens found a nest together after a mating flight. Typically,
many queens make mating flights at the same time so that many queens are establishing nests at the same
time, and so can easily co-found. The queens co-exist until workers emerge, then they normally start to
fight. As a result, “primary polygyny” normally results in “secondary monogyny”. That is, the result is a
nest with a single queen even though it was founded by several queens. (In a few species the queens do not
fight and co-exist in the same colony.) Ant foundress associations are an example of mutualism. A foundress
association can help the nest get off to a rapid start, by rearing more workers, which helps the colony to
survive the very risky founding stage. In may ants there is much colony death during the founder stage due
to intraspecific competition and brood raiding. Many queens may establish nests in an area big enough for
only a few mature colonies. This is similar to what happens when many seeds sprout in an area too small for
all the young plants to survive.
To see how co-founding can be mutualistic, consider this example. A nest co-founded by two
queens has three times the chance of surviving the founding stage. Then the queens fight and one survives.
Both queens have an equal chance of winning. The average fitness of co-founding queens is then 1.5 times
(3/2) than of single-founding queens. The co-founding queens enter into a lottery in which the price of
buying a ticket is less than the average payout. If the co-founded nest had only 1.5 times the chance of
surviving it would not be worth co-founding.
In Halictidae bees and Polistes wasps, foundress associations often form in the spring when nests
are founded by overwintered females. In contrast to the ant situation above, the queens are often sisters who
were reared in the same nest and recognize each other (nestmate recognition) in the spring by their
distinctive blend of cuticular chemicals, some of which they acquired from their natal nest making them
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C1139 Social Insects. The Society. Lecture 4
have a similar odour. There is usually a dominant individual and one or more subordinates, who do more of
the work and less of the egg-laying.
Colony fission: founding by queen(s) and workers
In many ants, one or more queens plus a group of workers establishes a new nest close to the existing nest.
For example, the clusters of wood ant (Formica lugubris) colonies that you may have seen on field trips to
the Surprise View at Hathersage, in the Peak District near Sheffield. This is typically associated with
polygyny (nests with multiple queens). You can sometimes see workers carrying brood walking along trails
connecting the nests.
In some species of ants, such as Eciton and Dorylus army ants, the queens have completely lost their
wings, and colonies are only formed by fission, never by a queen or queens alone.
Colony fission: founding by queen(s) and workers: swarming
In honey bees (Apis), stingless bees (Meliponinae), and Epiponini wasps (a tropical American group of
Polistinae wasps) colonies are founded by a swarm. That is, a mass of workers who leave the parental nest
with one or many (Epiponi) queens. Swarming has evolved multiple times. In many swarming and budding
species the colony cannot function without workers. A honey bee colony cannot function at all with less
than approximately 1000 workers. An Ecition army ant colony cannot function with less than approximately
100,000 workers. In this species, their social life has evolved to such an extent that small colonies cannot
survive.
Swarming can also be used for colony relocation, without colony fission. The whole colony leaves
an unsuitable nest site. African honey bee, Apis mellifera, and Asian giant honey bee, Apis dorsata, swarms
may even be migratory, with the whole colony travelling up to hundreds of kilometers to a more favourable
location in terms of flowers. In Apis dorasata the migration is seasonal with the swarms returning several
months later to where they originally set out from. Amazingly, an Apis dorsata colony nesting in one
particular tree may leave, and come back to exactly the same tree months later.
Reproductive swarming in the honey bees and stingless bees
This usually occurs in spring in temperate areas, late April to June in England. The mother queen and
approximately two thirds of the adult workers leave the nest in the "prime swarm". It takes just a few
minutes to leave the nest. The bees form a cloud in the air, but rapidly settle in a cluster usually on a nearby
bush. (At the time the swarm departs the original nest contains c. 10-20 pupal queens. When these hatch
none, one, or a few additional swarms, known as “casts” or “after swarms”, may depart each headed by a
virgin queen. One of the newly-reared queens takes over the original nest.) Scout bees on the swarm now
look for cavities in trees and other locations as potential nest sites. One is chosen, usually within 1km, by a
complex decision making process in which a whole range of parameters, including cavity volume, height
above ground, size of cavity entrance, and entrance orientation are evaluated. The swarm then moves to the
new cavity and in just a few minutes the bees, on average about 10,000, all pile in. Overnight, using wax
from their wax glands, the colony will build its first comb and the queen will start laying eggs. The swarmfounded colony is in a race against time to build up its population and honey stores before winter. In
northern areas most swarm-founded colonies die out in their first winter due to starvation.
In stingless bees (Meliponinae) swarming is more gradual. A colony locates a suitable nest site and
gradually builds combs and food pots while maintaining contact between the new nest and the old nest.
Eventually, a young queen, not the mother, flies over to the new nest to join the workers there. The process
can take weeks, even months. Stingless bees and honey bees are close relatives. But the large differences in
their swarming behaviour suggest that swarming evolved independently in each group.
Parasitic nest founding
It is common for queen Vespinae wasps and bumble bees to steal a nest being founded by another queen of
the same species. In addition, both Vespinae wasps and bumble bees have species that are workerless
parasites and take over the nest of other species. The workers of the deposed queen rear the young of the
usurping queen even though they are of another species. In Britain, the cuckoo wasp Vespula austriaca is a
workerless parasite of Vespula rufa, the red wasp, and there are also several parasitic species of bumblebees
in Britain. There are also workerless ants parasitic ants. In addition, in many ants that do have workers a
queen may found her nest by taking over the nest of another species.
In the workerless parasitic species eusociality has gone over to parasitism. It should not be a
surprise that social parasitism occurs. Workers can rear the offspring of another female, in just the same way
that parents can, as in the cuckoo. In some ants, such as the British wood ant Formica sanguinea, workers
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raid colonies of other wood ant species and capture pupae. The pupae emerge in the F. sanguinea nest and
work even though they are helping to rear brood of another species. This is known as slavery or “dulosis”.
Workers in some ant species, such as Polyergus, cannot work. All they can do is raid other nests. All the
work is done by the allospecific slaves. In F. sanguinea workers can still work if they have to. Anyone
interested can read in Origin of Species some simple experiments that Charles Darwin did on F. sanguinea.
Colony life span: Annual
Annual nests are founded in spring and die out in the summer or autumn. The colony first rears workers then
queens and males. This is a common life cycle and occurs in Bombus, Vespinae wasps, Polistes wasps, and
most eusocial Halictidae bees. During winter all that remain are young inseminated queens. The young
queens and males are reared in the summer or autumn, leave the parental nest, and mate. The males die and
the inseminated females overwinter.
Colony life span: Perennial
Perennial means a colony that can live for more than one year. Colonies of termites, ants, Apis and
Meliponinae bees, some Halictidae bees and Epiponini wasps are perennial. In these bees and wasps and
some of the ants the colony can replace the queen if she dies. These colonies are potentially immortal, but
still perish by being predated, starving, or by something going wrong during the queen replacement process.
Four stages of the colony life cycle
Oster and Wilson (1978) characterize four stages in the life of an ant or social insect colony. Again, there
are analogies to the life cycle of a multi-cellular organism.
Founder
Queen(s) and brood only.
Ergonomic
Workers present. Colony is growing but rearing only workers. Lasts just a few months in
annual species, but can last several years in large-colony ants such as Atta leafcutter ants. In perennial
colonies there may be an ergonomic phase and a reproductive phase each year.
Reproductive Colony is producing queens and males.
Orphaned/queenless
A colony in which the queen has died and cannot/has not been replaced. In many
species (e.g. Apis mellifera) the workers now lay many eggs that are reared into males. Because no female
eggs are being laid the workforce dwindles and the colony dies out. In some annual species (Bombus, Vespa,
Dolichovespula) workers may actually kill the queen and take over egg laying.
Colony kin structure
We will return to this in a later lecture in the second section of the lecture course. Today we will just touch
on this important topic. Kin structure can be a description of a colony in terms of family relationships. For
example, the workers are all offspring of a single queen mated to a single male. It can also be a description
in terms of relatedness among specified individuals. For example, the relatedness among workers is 0.75.
Note that different kin structures may give the same relatedness. For example, both multiple mating by a
single queen and multiple queens reduce relatedness among workers.
Examples
The simplest colony kin structure is a single queen mated to a single male. All workers are the offspring of
this pair. This is a very common type of kin structure, found in many ants (e.g. the fire ant Solenopsis
invicta), almost all Meliponinae bees, bumble bees, and Polistes wasps. In some of these species the males
are all the queen’s sons, and in others some or many young males are also workers’ sons.
It is also very common to have a single queen mated to more than one male so that the workers all
have the same mother but have two or more fathers. In many species most queens are mated to one male,
with a small proportion being mated to two males (e.g., in some Vespinae wasps such as the hornet Vespa
crabro, Dolichovespula). In common wasps, Vespula vulgaris, the queen is normally mated to several
males.
Extreme multiple mating by queens (>5 males) has evolved multiple times and is is found in a few
taxa including Apis honey bees, Dorylus and Eciton army ants, Acromyrmex leafcutter ants, Pogonomyrmex
seed harvester ants, Cataglyphis desert ants, and some Vespula wasps. In Apis the workers have one mother
but 10, 20 or even 50 fathers.
Why is there so much variation in queen mating frequency and why has multiple mating evlved on
some species? A lot of work has been done on this topic but we will not cover this topic in the course.
In many ants, colonies have more than one egg laying queen. This is also common in Epiponini
wasps but not common in bees or other eusocial wasps.
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