What is a parasitoid?
A parasitoid is an organism that has young that develop on or within another organism (the host), eventually killing it. Parasitoids have characteristics of both predators and parasites.
In general, parasitoids share the following features:
- Parasitoids are usually smaller than their selected host.
- Parasitoids are very selective and only attack a particular life stage of one or several closely related species.
- Adult parasitoids are generally either nectar feeders or predators.
- Only female parasitoids are involved in finding and using the host.
- Generally the host does not die until the young are fully grown and ready to become adults.
- Parasitoids can sometimes prevent larval hosts (e.g. caterpillars) from developing, until the parasitoid is fully developed.
Which invertebrates are parasitoids?
Parasitoids include species of wasps, flies (e.g. tachinid flies), beetles and worms (e.g. gordian worms).
What do parasitoids target?
Parasitoids target other invertebrates, although a few (e.g. a species of rove beetle) are known to infect snake eggs . Parasitoids usually target certain groups, for example spider wasps infect spiders and cuckoo wasps infect other wasps. Some even specialise in targeting hosts that are already infected.
How do parasitoids infect their hosts?
Parasitoids infect their hosts using one of the following three methods:
- Eggs are laid in, on or near host eggs and young.
- Eggs are laid on plant species visited by the host.
- Eggs are laid in, on or near adult hosts, which have been stung and paralysed.
Parasitoid larvae hatch and grow by feeding on the bodily fluids or the internal organs of the host (usually the non-vital parts first). The host dies when the fluid has been sucked dry or its internal organs cease to function.