What are parasites and parasitoids?
Some animals and plants survive by obtaining their nourishment from other organisms – or ‘hosts’. The majority of animals which follow this lifestyle are invertebrates. While we understandably think initially of the negative effects these animals (such as Bed bugs or ticks) can have on humans, it is important to remember that the majority of these invertebrates only affect other animals and plants – particularly other invertebrates!
These animals are absolutely fascinating, with amazing life cycles!
There are two quite different lifestyles taken by such animals, which are known as either ‘parasites’ or ‘parasitoids’, depending upon which approach they follow, although both may live either inside or outside of the host animal.
Click here for a list of different invertebrate groups that include parasites and parasitoids.
|An Ichneumon parasitoid wasp (Diplazon laetatarius) © Roger Key|
Parasites and parasitoids: What's the difference?
The following sections will show you how to tell the difference between parasites and parasitoids.
A parasite obtains its nourishment from a host organism without benefiting or killing the host, and does not prevent reproduction.
Parasites often have interesting and complicated life cycles, which may involve a number of different host organisms.
A wide range of animals are parasites, including many invertebrates, such as species of flies, ticks, mites and various types of worm (including leeches).
|A tick (Ixodes sp.) © Roger Key|
While the vast majority of parasites do not affect humans, some are responsible for diseases in people.However, viruses and bacteria are not normally considered as parasites.
To learn more about parasites, click here.
As with parasites, parasitoids spend a part of their life obtaining nourishment from a host organism – however, unlike parasites, parasitoids ultimately kill their host and prevent reproduction.
|Polysphinctine parasitoid wasp larva on spider host © Roger Key|
Almost all parasitoids are insects, and most are wasps. However, parasitoids include other invertebrates, such as species of flies, beetles, moths, mites and worms.
Parasitoids are not known to be responsible for any human diseases, but instead are very important for controlling agricultural pests. Although some viruses and bacteria do follow similar life strategies, they are not generally considered as parasitoids.
To learn more about parasitoids, click here.