They are everywhere, they come in groups, they bite, and, once in your house, they are very hard to get rid of. No matter how annoying ants sometimes are, they can also be fascinating and a lot of people might have spent some time idly wondering about ant anatomy and pondering questions, like do ants have bones?
Do ants have bones? Yes! But not in the way humans and most animals have bones. Ants, like other insects, have an exoskeleton, which means that their skeleton is on the outside of their body. The exoskeletons of insects like ants or beetles are made of a hard, water-proof substance called chitin.
Some things are the same whether a skeleton is on the outside or the inside of a body: just like your skeleton, which, being inside of your body, is technically called an endoskeleton, an ant’s exoskeleton provides an anchoring point for the muscles and is central to holding the body together. Of course, an exoskeleton also has its special benefits as it provides the inner organs with protection against attacks.
What Other Animals Have Exoskeletons?
There are, of course, mainly insects that have an exoskeleton. Grasshoppers, centipedes, cicadas, beetles, or cockroaches are examples of these.
Other animals with exoskeletons are crustaceans like crabs or lobsters. There are even animals like turtles, armadillos, and pangolins that have both an exoskeleton and an endoskeleton!
Do Exoskeletons Grow?
No, they do not. Different animals have found different solutions for handling the problem of living and growing when stuck in a rigid shell. Some animals live in shells that are open, like snails for example. These can add new materials to the shell – a snail, for example, secretes calcium carbonate which is added to the shell.
While you could thus say that the shell technically does grow, after all, it does so differently than when it comes to the growth of animals with endoskeletons. When human beings and other mammals grow, the bones actually get bigger and longer, whereas the shell that a snail started out with never actually grows in size. Even when no material is added to it, the diameter of the very first swirl the shell started out with stays the same!
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In animals like insects where the whole body is covered by a closed exoskeleton, the skeleton cannot grow and has to be shed or molted. When an insect leaves its old exoskeleton behind, the new one starts out to be soft and flexible but then hardens.
Molting does not only happen in animals with exoskeletons – snakes and frogs, for example, regularly shed their skin. While one reason for molting is the fact that exoskeletons do not grow, it is also a process of growth that allows the same animal to look very differently at various stages of its life.
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Which Animals Count As Insects?
Insects are animals that are invertebrate arthropods with three pairs of legs. But what do all these words mean?
When researching the skeletal structure of various animals you are sure to come across the terms vertebrate and invertebrate. Vertebrates are animals that have a backbone like humans, other mammals, birds, or reptiles. Invertebrates are animals without backbones, like insects, spiders, worms, and crustaceans.
Once you know that you are confronted with an invertebrate, the next step is to figure out whether it is an arthropod. Arthropods are invertebrates that have jointed legs and an exoskeleton. Now you can exclude invertebrates like worms which have neither legs nor an exoskeleton.
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Lastly, you have to decide between insects, spiders, and crustaceans. This is a matter that comes down to the number of legs an animal has.
Spiders have four pairs of legs, which makes eight legs in total. Crustaceans have five pairs of legs, which makes ten legs in total – in some species, though, the front pair has been modified to a pair of pinchers, be sure to count them!
Insects, lastly, have three pairs of legs, which makes six legs in total. The next time you find yourself confronted with some creepy-crawly, all you need to do is answer the questions “How many legs does it have?”, “Does it have an exoskeleton?” and “Does it have a backbone?” and you can impress everyone around with your knowledge about many-legged animals.