How are ants developed into adults?
Much like butterflies, ants go through a complex metamorphosis before they are considered full-grown and ready. The time it takes from egg to ant varies, but all the different species share the same pattern.
There are three phases that every ant goes through before it can be considered complete and ready to start its service to the colony. The queen is the mother of all colony members, and for the most part, lays all of the eggs. The time from egg to an ant is not the same in every species, but a well-known example is the black garden ant (Lasius niger) which takes approximately eight weeks to finish the process.
The development is divided into three stages. The first stage is the egg, followed by the larvae which is in turn followed by the pupae. When these are through the ant is ready for its life to begin.
An image of the development of the species Pseudomyrmex gracilis. Their pupae do not spin cocoons but rather develop without any protection. Archibald Biological Station, Florida (USA). Photo: Alex Wild.
1. The egg
The eggs are tiny. They have an oval form with a sticky surface. The stickiness serves as glue when several eggs are put together, making it easier for the workers to carry many eggs at a time. This is very practical and crucial in times of nest invasion when brood needs to be transported to safety as quickly as possible.
The queen is also able to lay trophic eggs. These eggs are made for eating and are not fertilized. It might seem an odd thing, but they are quite useful. For example, when the queen is founding her colony, she is unable to go out foraging. She then converts her wing muscles into eggs, which she can eat and get nutrients from. They are also great for feeding the larvae when no other food is around. In some cases, workers have been known to lay trophic eggs and feed them to the queen. (1)
2. The larvae
When the egg is ready, it will slowly transform into a larva. They are, just like the egg, white but differ from it in length. The larvae are transparent, long, and shaped like bananas. They are equipped with small hairs serving the same functions as the glue of the eggs. Thanks to the hairs they can be attached, to walls or floors. Their mobility is certainly restricted, but they can move their head to turn their mouth toward food. (2)
Larvae are for the most part being held near the eggs. They form piles where the larvae might accidentally eat some of the fertilized eggs. The larval stage consists of four stages, during which the workers feed them with liquids. They need a lot of protein to be able to grow into the body of an adult ant. Some ant species feed their larvae with solid food which they have chopped into small parts to make it easier to consume. The larvae are also known to emit liquids – some sort of feces – that the workers either consume or throw away. One of these is floury and seems to be very attractive to the workers, which gather around to taste it. If not floury, the liquid is transparent and seems not to interest the ants, which throw it away outside of the colony. (3)
3. The pupae
The third and last stage of an ant’s development is the pupae. During the end of the larval stage (pre-pupae), the larvae become inactive and get rid of the poisons they’ve collected during that stage. This forms a black dot, visible to the human eye. Some ant species have larvae that spin cocoons, while others don’t. The common north European woodland ant Formica rufa is an example of cocoon-spinning species. The pupae start out white, as the larvae, but darken over time. (4)
In other species, cocoons are not used during pupae. They are out in the open and their development can easily be observed. All pupae are positioned in a fetal position with lowered heads and bodies shaped much like a banana. The cocoon-spinning ants look the same although they are covered by the shell of the cocoon.
Some of the more exotic species find another use for the larvaes' cocoon-spinning abilities. The fabric of the cocoon is of a fine silk thread which the larvae can produce at will (although they probably don’t think very much about their actions). So instead of the larvae using the silk for cocooning, they are used by workers of the colony to glue together parts of the nest. The weaver ants, for example, located at the top of trees, tie together large groups of leaves to create a nest high above the ground. The ants carry the larvae with their mandibles and use them as gluing devices.
When the pupae are fully grown and have begun to darken, they will wake up. For the first days of its life, it will be lightly colored and transparent in comparison to the other members of the ant colony. But after a few days, it will darken and gain the same markings as its sisters. Most ant species let the new ants (also called nanitics) live their first time in safety, tending to the eggs, queen, and other inside duties of the colony. Then eventually they will look towards more dangerous tasks such as foraging or defending the nest. The closer one ant is to death (by age), the more economically motivated the colony is to risk its life.
References
1. Bert Hölldobler & Edward O. Wilson (1990) “The Ants” p. 168
2. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 34 (Swedish)
3. Bert Hölldobler & Edward O. Wilson (1990) “The Ants” p. 167
4. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 34 (Swedish)
Further reading
Images of eggs, larvae, and pupae: Alex Wild Photography (Brood)
