Arthropods are invertebrates. They are bilaterally symmetrical (split down the middle each half is identical). They do not contain an internal skeleton for support but rather have an exoskeleton. Their bodies consist of segments with each having a pair of appendages. Because of the presence of an exoskeleton that is rigid, Arthropods need to undergo stages of development. This results in the shedding of the exoskeleton to reveal a new version for each new stage of development. This is called moulting and can be described as the process of maturation via the transformation to various stages of development. Most Arthropods are void of wings. The diversity of the Arthropods is great with an estimated over 10 million species present, many not yet discovered.
The Arthropods can act as parasites and are described as ectoparasites in that when they are parasitic they are found outside of the body (hair, skin). Other organisms such as the Protozoa, Helminths, etc… are parasites that are located inside the human body. Some Arthropods are important vectors of diseases and other parasites. And still other Arthropods are not vectors or transmitters of disease but are considered a nuisance. Bedbugs are an excellent example of an arthropod that is not known to transmit disease but rather is a nuisance. Regardless, Arthropods are important vectors of diseases that include bacterial, viral, and parasitic organisms.