Parasitic wasps are
part of the group we call beneficial insects. They
lay their eggs in or on other living insects. When
the eggs hatch, they burrow into the host and begin
to feed. Eventually, they kill the host and, if it
is an insect we consider a pest such as a tomato
horn worm, that is beneficial.
Most people look to
ladybug beetles, praying mantids and lacebugs as
prime examples of beneficial insects, parasitic
wasps are much more efficient at the job.
species exist that feed on
certain caterpillars and many other insect species.
You can purchase eggs of certain parasitic wasps
commercially to spread around your garden. However,
remember that, if you choose to go this route, you
need to stop using regular
insecticides that will
kill the beneficial insects before they get a chance
to do their thing.