Generally ant brood go through 4 stages as they develop: egg>larvae> pupae (or, in some species, cocoon)> adult.
Ant eggs are tiny at approximately 0.5 mm in diameter and weighing about 0.0005g, and are kidney shaped. They have a smooth sticky surface which enables them to bond together in a mass which aids adult ants to move them about more quickly, in case of emergencies for example; it is easier and quicker to carry many eggs in one go rather than having to pick each individual egg up.
After about 7 to 14 days of cell division the larvae will emerge from the eggs looking very much like tiny maggots. As they grow they shed their skin, usually about 3 times in all, increasing in size with each moult from 1 mm to 4 mm. With each successive moult they become more hairy, with some of the hairs being hooked to enable, like the eggs, numbers of larvae to hook together for easier carrying, however, at the last moult the larvae are usually too heavy to hook together, and are carried singularly. There are some slight differences in the appearance of the larvae of various ant species, for example some are hairier than others. The larvae have no legs but they are capable of some very small movements such as bending their head toward a food source and, in some species, they can move along very slowly if necessary. When they feed they suck up the juices of solid foods brought to them by the adult worker ants, or they can receive regurgitated food from them. Larvae have large digestive glands with reservoirs that run the full length of their body opening at the mouth. Larvae can exude a clear saliva which is used to break down and digest protein which is mixed with the food it eats. A worker ant can encourage the production of this saliva by gently pushing back the larva's head or nipping it in that area.
In various places throughout its body the larvae has little buds which later develop into antennae, legs and various organs. These later elongated, join together and secrete the pupa skin, causing the larvae skin to be cast off. This larvae skin is then taken out of the nest and dumped outside looking like globules of sticky fat. The pupa skin sets hard and the adult ant is constructed within. As time goes on these develop to look like folded up waxy ants. As the time for "hatching" nears this waxy-like ant will darken and unfold itself.
After about another 24 to 27 days, once the larvae have gone through all of the skin moults, they change into one final stage which is the pupae. Pupae look like white waxy ants that lay with their legs and antennae folded up against their bodies. Some species, such as Lasius niger, do not have a pupa stage but the larvae will spin themselves a cocoon in which it will metamorphosis into the adult ant. To be able to spin a cocoon the larvae must be against a solid object, this could be the ground, wall of a chamber or, in some cases, the larvae will be buried in the soil to assist them in the spinning of the cocoon, only to be dug up again by the adult workers once the cocoon is completed. The larvae will eject all its gut contents out and this appears as a small black dot at one end of the cocoon.
After, approximately, a further 13 to 28 days (about a total of 8 to 12 weeks from egg to adult ant), and again this varies according to species and ambient temperatures, the adult ant emerges looking very pale and soft. A newly born Lasius niger ant is almost white at first but after a few hours it will darken to black and it's exoskeleton will harden.
The particular job that each worker does within the colony depends on its age. New ants tend the queen and brood within the security of the depths of the nest. As the ant gets older so it will change jobs which take it nearer the surface of the ground until, nearer the end of its life, the ant will leave the safety of the nest and forage outside. This is