Parasitic Wasps
Parasitic wasps are tiny, stingless, and precise, with each species targeting a specific host pest. These guides cover how they work and which ones matter for gardens and greenhouses.
Allies you will rarely see and never feel. Most are smaller than a grain of rice, cannot sting you, and end specific pests from the inside.
Size
Often under 3 mm
many almost invisible
Species
Tens of thousands
likely far more unnamed
Diet
Host aphids, caterpillars, grubs
roughly one host each
Habitat
Wherever the host lives
gardens to greenhouses
Sting
Cannot sting people
the ovipositor targets hosts
Life cycle
Four stages, most of them spent inside or on another insect.
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Egg Laid in or on a host insect with a fine, needle-like ovipositor.
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Larva Feeds inside the host, growing as the host slowly gives out.
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Pupa Spins small cocoons, often clustered on the spent host, like the white studs on a hornworm.
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Adult A tiny wasp that flies off to find the next host. It cannot sting you.
A tomato hornworm studded with little white cocoons looks like something has gone wrong, but it is the best news a tomato grower gets: braconid wasp larvae have finished with it from the inside. I leave those hornworms exactly where they are, every time. It feels backwards the first year, and then you watch the next generation of wasps handle the whole bed.
Sam Fielding · field note · about Sam
Typical season
Active through the growing season, tracking their host pests wherever those appear.
A parasitic wasp finds one particular pest and ends its whole line from within, which is how a hornworm covered in white cocoons becomes good news for a tomato grower.