Ants

Ants fast facts

  • They have a narrow waist formed of 1 or 2 segments called the pedicel, see the drawing below.
  • Antennae are strongly elbowed.
  • All species live socially.
  • "Ants eggs" sold as fish food are actually ant pupae (usually of the wood ant Formica rufa), in their cocoons.
  • Earliest fossil remains are from 120 million years ago.
  • Ants were the first farmers. Fossil evidence shows they were farming fungus 80 million years ago, and feeding the fungus on insect faeces and dead insects.
  • Ants create and fertilise the soil by recycling nutrients.
  • Adults range in length from 1 mm - 25 mm.
  • There are around 9 - 10,000 described species worldwide, and 60 species in the U. K. (this includes 10 alien species).
  • A queen ant can live for as long as 15 years.
  • Adult males and queens have wings, but after the nuptial flight the queen removes her wings, and the males die.
  • In some species the queens and workers have stings, and in other species they can squirt formic acid from their rear end.
  • In the Amazon rainforest there can be more than 8,000,000 ants per hectare (Holldobler & Wilson, The Ants, 1990).
  • There are 1015 - 1016 ants alive in the world at any one time according to Holldobler and Wilson in the book Superorganism: The beauty, elegance and strangeness of insect societies (2009).
  • In some rain forests the biomass of ants can be 4 times the biomass of all vertebrates combined!

Ants farming aphids

The photograph on the right shows ants (Lasius niger) guarding aphids while the aphids suck sap from a rose bush. The aphids get too much sugar from the sap and excrete it (this liquid is called honeydew) and the ants lap it up; drinking some themselves, and taking the rest home for their nest mates and grubs.

The tip of every leaf was guarded by at least one ant, and other ants patrolled over the aphids, and up and down the stems. Any other insect, or even a camera strap would be nipped and squirted with formic acid. So the aphids are free to suck in peace and the ant gets a sugary reward. And the rose bush? Well it was quite a big bush and a short time later it had many fragrant blooms.

Ant life cycle

In temperate regions there is little visible ant activity during the winter. As the temperature rises sexual - males and queens - are produced, and these have wings. Sexuals from different nest are released at the same time. The conditions at the time of release

are usually warm, humid and still air and moist soil. This synchronous release from different nests prevents inbreeding. These mass flights of sexuals provide a good meal for birds, spiders and many other predators.

The males and queens fly off and mate. This is the only time the queen will mate, and the sperm she receives in this mating must last her a lifetime of egg laying, which may be more than 10 years.

After mating the queen lands and searches for a nest site. Before digging into damp soil she breaks off her wings. She will never need them again, and will probably never see daylight again.

She digs a small chamber in the soil and lays her first batch of eggs. The energy for this comes from the degeneration of her flight muscles. She tends her batch of white, sticky eggs, and when they hatch she feeds the larvae. During this time she doesn't eat or leave the chamber.

Once her larvae have pupated and hatched out as sterile female workers they will take over all the nest duties, and forage for food, leaving the queen free to concentrate on her only duty now, which is egg laying. The first workers are usually smaller than normal size for the species.

This is the typical life cycle, but there are variations. In the more "primitive" species the queen may forage in the early stages of the nest. In other species colonies may bud off the main nest to become satellite colonies. Some species raid other nests for slave ants which they take before the slave has hatched into an adult.

Ants farming aphids

Lasius niger, the common garden ant

On the right is a Lasius niger worker foraging for nectar on a sedum flower. This is probably the most common ant found in British gardens, and certainly the most common one kept as a pet.

The queens can only be seen in summer after mating. They are about 8 - 10 mm long and look very much like the workers.

The workers range from 3 - 7 mm long.

The males are 3.5 - 4.2 mm long.

They tend to nest under stones and paving slabs. And do occasionally stray into our homes if we leave food around.

As pets they are fairly easy to keep and will eat almost anything.

Lasius niger also feeds on aphid honeydew. To receive a droplet of honeydew the ant strokes the aphid's abdomen (see the photograph above). The ant will also remove ladybird eggs and larvae (a major aphid predator) from the plant the aphids are feeding on.

Lasius niger worjer, garden ant worker

The photograph on the right shows a Lasius niger queen ant with her wings still attached. As you can see the wings are longer than her body (the blue grid is in 0.5 cm squares), and smoky.

She will break off her wings and find a place to dig a small chamber where she will lay her eggs. I found her after we had had a few wet days, and the ground was soft for digging, but not saturated.

Queen ant with wings, Lasius niger queen ant with wings

Formica rufa, wood ant

On the right is an adult worker wood ant. This species does not have a sting, but can squirt formic acid out of its rear end, just below the anus. To do this it bends its gaster forwards between its legs. The accuracy is good up to a few centimetres only, but it can squirt up to 100 cm. This ant has very good eyesight.

Body lengths - males and queens 9 - 11 mm, workers 4 - 9 mm.

Formica rufa, adlut worker wood ant

It is commonly found in coniferous woodland. The nest is often built against an old tree stump, and the above ground part of the nest is mainly pine needles. The nest can extend more than a metre underground. Each nest can contain 500 000 ants.

Wood ant will eat almost anything, e. g. nectar, honeydew, seed that have an elaiosome (rich, oily food body attached to the seed to aid dispersal), insects, etc. Many woodland plants have elaiosomes, e. g. anemones, violets, primroses, and wood ants spread their seeds allowing the plant to colonise new areas. It has been estimated that ants from an average nest will transport around 36,000 seeds in one summer.

In captivity a Formica rufa queen reached 15 year of age before dying, and may live even longer in the wild.

Pharaoh ant, Monomorium pharonis

Right is the Pharaoh ant, Monomorium pharonis. It was introduced to the UK over 100 years ago from the tropics. It is a small ant, the workers are 2.0 mm long, queens 3.6 mm long, and males 3.0 mm long. It is light yellow in colour.

There are usually many queens in one nest, and many of the nests are linked to each other and exist quite happily together.

Sexuals are produced throughout the year. Around 300 eggs are laid by the queen in batches of up to 12 at first, but later as few as 4.

The eggs hatch in around a week. The larvae take around 18 days to reach full growth. Pupation takes around 9 days, and adult life span is usually 5 - 6 weeks.

Mating takes place within buildings, in crevices and cracks. In the UK it is found only in heated buildings. The nests are usually in difficult to locate places and as they are linked to other nests eradication is difficult.

an adult Monomorium pharonis, the pharoh ant

The secret of ant success

  1. Division of labour. Whether it is farming (aphids, etc.), food processing (fungus), or predation, ants divide up the task to achieve their aims.
  2. Modification of their environment to better suit themselves and their livestock and food production. For example leafcutter ants use antibiotics and symbiotic bacteria to protect their food crop of fungi. Weaver ants make their nests by stitching leaves together using their larvae to produce the silk thread.

Ant communication

Communication is mainly done by chemicals called pheromones. There are chemical trails to food sources, trails during exploration, and chemical alarm warnings.

The chemicals are produced in various glands, e. g. cloacal, Dufor's, poison, rectal, and tibial. Grooming and trophallaxis (liquid food exchange) also spread chemicals of recognition and queen condition throughout the colony.

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