Some wasps are parasitic. The cuckoo wasps (family Chrysididae), of worldwide distribution, are brilliantly colored wasps that lay their eggs in other wasps' nests. The ichneumon flies are wasps that lay their eggs in the larvae of other insects. The gall wasps (see gall) lay eggs in plant tissues. Wasps that prey on harmful insects have been introduced in various regions to control these pests.
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