How are ants built?
The anatomy of ants is captivating. Even though their skeleton is on the outside of their body, they are very flexible. This exoskeleton encapsulates the ant’s inner organs and muscles and serves as protection against attacks.
The exoskeleton is a fundamental part of the anatomy of ants, providing a hard surface protecting the ant’s insides from the outside. Rather than our human approach to skeletons (like having them on the inside for starters), many insects carry them on the outside. But just like ours, it is central to holding the body together, providing anchoring points to muscles. (1)
Ants can easily be discerned when looking at a group of insects. They have a distinct and unique body type with a head, thorax, and abdomen. But what makes the ant different from other insects is first off the segment between the thorax and abdomen: the petiolus (some species also have the so-called postpetiolus). Second: their antennas, bent much the same way as our knees.
Petiolus and postpetiolus are very small and might not always be easy to spot in some species. But despite their size, they are highly important to the flexibility of the ants and a crucial part of their warfare. The petioles give them the ability to bend their abdomen under their body, making it possible to spray the enemy with poison from their abdominal glands. (2)
This is a highly up-close image of the small segment called the petiolus. It is what makes it possible for ants to be flexible with their abdomen. Also shown are holes serving as antibiotic glands. Photo: Alex Wild.
A breakdown of the ant's anatomy
Ants have compound eyes (facet), much like flies. The size of them varies depending on the species. The woodland ant of Formica rufa for example carries large eyes, whilst the ones of the yellow meadow ant Lasius flavus are tiny. This is most probably a result of the latter spending all of their lives in the darkness of their tunnels. Queens and males also have an extra three ocelli – forming a triangle – small eyes whose true purpose is disputed. (3) They do not seem to give the ants any sort of visual images of their surroundings but rather take in light. Nocturnal dragonflies have well-developed ocelli, which might be a clue to their true purpose of navigational guidance. (4)
The anatomy of ants may be very different from the one of humans, but they have small similarities that might aid in the understanding of their different body parts. For example, the antennas have the same function as our knee, bending in the middle. When continuing from the ”knee” one discovers a bunch of small segments differencing between species (Formica rufa has 11 segments).
Another important part of the anatomy of ants is the jaws or mandibles. They have two large mandibles, an upper lip (covered up), a pair of lower mandibles (maxilla), and a lower lip (labium). The mandibles are dented and used to kill prey and enemies, “sawing” materials and to get a good grip during transport. On the lower lip and lower jaw are two palps. They look like small segmented antennas hanging from the mouth of the ant.
The anatomy of ants usually serves as the example insect when talking about their body construction. Their three body parts (four or five when counting the petiolus and postpetiolus) together with their six legs form a clear and symbolic icon of the insect world. The legs are all anchored in the thorax and consist of a hip, a femur (thigh bone), a tibia (shinbone), and segments of the foot. At the end of it is a spur, serving as a great tool when cleaning the antennas. When studying ants you will quickly see a display of this cleaning ritual. They are much like cats in that sense, constantly grooming themselves. (5)
The anatomy of ants – inner organs
Ants do not have a heart like we do, or other mammals for that matter. Instead, they have one big (in ant measurements) artery, starting from the brain, working its way through the body parts. Their blood is not red either, but rather uncolored and transparent.
Much the same way as the ”heart” artery goes through the body, the ants have nerve fibers flowing through the brain and muscles, providing means of communication between the brain, organs, and muscles. The stomach is located in the abdomen with most of the other large organs. (6)
Instead of lungs, the ants have small openings in their exoskeletons that circulate oxygen through the body. This means that the ants do not draw breaths, but rather let the surrounding oxygen pass through them.
1. Myrors anatomi – Wikipedia (Swedish)
2. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 29 (Swedish)
3. Naturhistoriska riksmuseet – Insekters sinnen (Swedish)
4. Punktögon – Wikipedia (Swedish)
5. Per Douwes, Johan Abenius, Björn Cederberg, Urban Wahlstedt (2012) Nationalnyckeln “Steklar: Myror-getingar. Hymenoptera: Formicidae-Vespidae” p. 29 (Swedish)