Parasitic Wasp
Predator
Parasitic wasps are tiny, often unnoticed allies that use aphids, caterpillars and other insects to raise their young. They are harmless to people and do not behave like social wasps around food. By naturally limiting pest populations, these specialist insects help protect vegetables, fruit and ornamentals while supporting a complex garden food web.
How to identify it
Most parasitic wasps seen in gardens are only 1-10 mm long, slender and dark, though some are yellow, orange or metallic. They have clear wings, narrow waists and long antennae, but are much smaller than familiar social wasps. Females lay eggs in or on a host insect. The developing larva feeds there, then pupates and emerges as an adult. Aphid "mummies" are swollen, papery brown or gold cases with a neat exit hole.
How it helps your garden
Different parasitic wasps target aphids, caterpillars, whiteflies, sawfly larvae and other pests. Their young develop at the expense of the host, reducing pest numbers before outbreaks become severe. They are especially valuable in mixed vegetable and flower gardens where host insects and nectar sources occur together. Their work complements hoverflies, ladybirds and lacewings rather than replacing them.
How to attract it
Plant small, open flowers with accessible nectar, such as alyssum, dill, coriander, fennel, yarrow and wild carrot, using RHS Plants for Pollinators where appropriate. Maintain flowering strips and allow a few non-damaging aphid colonies to remain. Keep hedges, leaf litter and varied vegetation for shelter. Never use pesticides that kill these tiny wasps, their hosts or the other predators they work alongside.
Tips
Look for aphid mummies before removing a colony: they show that parasitic wasps are already at work. Leave affected shoots for a few days if damage is light. Their small size means they are easy to miss, so favour patience and plant diversity over instant intervention.
Parasitic Wasp: frequently asked questions
How does parasitic wasp help the garden?
Different parasitic wasps target aphids, caterpillars, whiteflies, sawfly larvae and other pests.
How do I attract parasitic wasp to my garden?
Plant small, open flowers with accessible nectar, such as alyssum, dill, coriander, fennel, yarrow and wild carrot, using RHS Plants for Pollinators where appropriate.
How do I identify parasitic wasp?
Most parasitic wasps seen in gardens are only 1-10 mm long, slender and dark, though some are yellow, orange or metallic.
General guidance for encouraging wildlife in UK gardens. Page updated 19 Sep 2026.