About Ants

Ants

Worker Ant - picture by kind permission of Bayer Environmental ScienceAnts, of which there are many thousands of species, are common to most of the world. The origin of the word ant is thought to have come from the word amaitjõ, "the insect that cuts (bites) off". The earliest evidence of the ant goes back 100 million years to the mid- to late-Cretaceous period.

Each species has quite different traits such as reproduction method and nest location. Their main predators are birds, small land mammals and other insects (including some other ant species).

Ants can be distinguished from other insects by the narrow section between the thorax (pedicel) and the abdomen (metasoma) and their bent antennae.

Like humans, ants are social creatures. An individual ant cannot achieve very much, but when working as a team, a colony can perform quite sophisticated tasks. Unlike humans, they are eusocial, where reproductive activity is carried our by a minority of the colony while the rest are sterile. The majority of ants are sterile female workers (sometimes calledsoldiers). The reproductive minority consist of a few drones - male winged ants - and one queen.

Colony sizes can vary from species to species from a dozen to a several thousand or even millions. Some species are scavengers while others (a minority) are predators or feed on specific foods. All ants have the ability to bite, often to eat vegetation, but in some cases to defend themselves or even in a predatory act. Some species will bite humans, such as Solenopsis invicta, the notorius fire ant.

A colony of ants can have organisational and physical properties that would challenge the abilities of a single instance of many more advance creatures. Some species have even been known to raid other colonies and domesticate their fellow ants as their slaves. This sophistication can only be achieved collectively. Some ants also farm aphids, allowing them to exist under the ants' control, while the ants feed from the sweet sap that they secrete.

In common with many species, global travel, especially it would appear, shipping, have distributed ants to parts of the world where they would otherwise not have existed. This has caused environmental imbalances, affecting local insects and crops.

The lasius niger is the common black garden ant seen in the UK and other parts of Europe. The majority of a colony is made up of workers. These are the sterile females that we normally see in gardens and occasionally in buildings.

In the early summer, the sexual female and males rise from thousands of nests and start to "dance" around each other in an excited airborne swarm. This is the mating ritual or the "nuptial dance" that lasts for 2 to 3 hours. Many of them are eaten by swooping birds.

Once mating has been completed, the surviving ants land and the male drones die. The impregnated female is now a potential queen. She rubs off, or bites off, her wings (these can be used as stored food) and searches for a suitable nest site. The sperm she now carries can be used for the rest of her life. As soon as she has found a suitable nest site, the potential queen -by now about 15mm long - makes a hibernation cell and starts to lay her eggs.

There are four stages of evolution from birth. Firstly there is the kidney shaped egg that weighs approximately 0.0005g and is about 0.5mm diameter. These eggs are sticky, allowing a mass of eggs to be bonded together. This means that the eggs can be handled in batches. This is useful if they need to be quickly moved out of danger or the nest is relocated, for example.

This is followed by the larvae, which look like tiny maggots. The larvae usually have three molts and with each molt they grow in size and gain tiny body hairs. Some of these hairs are hook-shaped. This again allows them to be bonded together. It is only at the last sub-stage of the larvae stage that they are too heavy for the hairs to hold them together; they are then handled individually. The larvae are fed by food brought by the workers. They either feed the food directly to them, or regurgitate food for the larvae to feed from.

The lasius niger do not go through a pupae stage. Instead, they spin their own cocoon. They can only do this against a solid mass. Soft soil is not sufficient. They need hard ground or very compacted soil. A solid wall is ideal. Alternatively, the workers can bury the larvae in the soil in order to allow them the opportunity to spin their cocoon, after which the workers dig them back out.

Most other ant species go through the pupae stage after the larvae stage. The pupae takes on a shape more resembling a mature ant, except that they have a white, waxy appearance, with their limbs and antennae folded inwards.

After a short while, the white ant turns to its adult colour, for lasius niger this is black.

The first to be born are sterile female worker ants. These young workers will not venture out from the new nest but will simply stay with the queen. As these workers mature, they will begin to venture to the edges of the nest and act as guards as the next generation of eggs are being hatched. Eventually, the oldest generation will venture outside the nest searching for food, whilst the younger ones guard the nest and the very youngest stay with the queen. Thus, the caste system, based on maturity of the worker ant, is established and a working pattern is formed.

The lasius niger is a foraging ant. The oldest workers will venture far from the nest in order to find food. If food is found - a sweet, moist food source is ideal - they will feed on it immediately if it is safe to do so. They will also carry food back to the nest. Other workers can smell the trail left by a foraging ant and will continue the food collecting duties pioneered by the successful pioneer.

Experiments carried out with pharaoh antshave revealed that they use geometry to navigate. They leave pheromone trailsthat are angled at between 50 and 60 degrees at forks in the trail. These angledforks allow foragers to find their way back to the nest by choosing the forkwith the narrowest angle.

Back at the nest, the food is shared with the rest of the colony. This sharing is done from mouth to mouth, or trophallaxis. Larvae are also fed through this method, using regurgitation, if necessary. 

The foraging expeditions of the lasius niger may take them into buildings, although it is more normal for them to stay outside and search in and around grass edges and stony areas, and modern times, in between paving stone cracks.

Throughout the rest of her life the queen stays at the centre of the nest being protected by her family, and hatching eggs. The rate of this hatching is dependent of external conditions such as safety and temperature.

In late June or early July the lasius niger queen lays fertile female and male eggs. These fly off in search of mates from other colonies and the "nuptial dance begins again.

Ant lifespan varies widely according to species, sex and caste. Workers may only live a few weeks, for example. The lasius niger queen can live for up to 15 years.