Arthropods are a genus of animals. They include insects, millipedes, crabs, and arachnids. That’s four classes. The fifth class, the trilobites, are already extinct. Four-fifths of all animals in the world are arthropods.
Arthropods are found all over the world. Many are considered beneficial to humans, especially the insects that pollinate the flowers. We also eat some species, such as lobster or shrimp. We get honey from bees and silk from silkworms. In other countries, people like to eat different arthropods. Here, too, they are becoming more and more common on our plates, such as grasshoppers or mealworms.
But we also consider others to be pests: certain beetles damage the forest, and aphids suck the sap from the leaves of garden plants, causing them to die. When the mealworm eats our food, it is no longer considered a benefit, but also a pest.
What is the body of the arthropod like?
Arthropods have an exoskeleton. This is a shell like that of mussels or hard skin. They have to shed them again and again in order to be able to grow. Your body is made up of different parts called segments. You can see them very well in bees, for example. They have legs on one or more segments, clearly visible in millipedes.
Many arthropods breathe through tracheae. These are fine air channels that lead everywhere through the skin into the body. This supplies your body with oxygen. This happens “automatically”, which means that these animals cannot breathe in and out consciously. Other arthropods breathe with gills. Like fish, they can use it to breathe underwater.
Most arthropods have antennae, also called “feelers”. Not only can you feel something with it, you can also smell it. For some, these antennae consist of multiple links that they can move individually. Few arthropods do not have antennae. With them, the front legs take over these tasks.
Arthropods have a single-cavity heart. It doesn’t pump blood, but rather a similar fluid through the body called hemolymph. They say “hemolums”. The digestive organs include a stomach, or just a crop, which is something like a pouch for food. Then comes the gut. There are also organs similar to the kidneys that eliminate water and waste. Feces and urine leave the body through the same exit, the cloaca.
Arthropods come in males and females that mate to produce young. The female lays eggs or gives birth to live young. Some parents take care of their young, others leave the eggs to fend for themselves.