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Beneficial Insects You Need to Know – Part 2

Back in April you read Part 1 of this series about beneficial insects you can encourage in your yards. I discussed predatory insects: lacewings, mantids, ladybird beetles, pirate bugs and syrphid flies. All of these are active hunters of garden pests. Now we need to shift our focus to the parasitoids – those insects who parasitize other insects. In this instance, females of the parasite find a suitable host insect – usually a caterpillar – and lay their eggs directly in the body of the host.  The host remains alive while being eaten from the inside by the larvae of the parasite. Not a pleasant vision, but one uniquely designed by nature to maintain ecosystem balance. Examples of parasitoids are parasitic tachinid flies, braconid, chalcid, Ichneumonid and trichogramma wasps.


Tachinid flies are quite variable in appearance but are usually very bristly. Adult flies feed on nectar and are important pollinators in your garden. Female flies lay one to several eggs in a host caterpillar or similar larva.  Those eggs then hatch and the fly larvae feed on the living host until they are ready to pupate, at which point they emerge, finally killing the host insect.







Parasitic wasps range in size from small to minuscule and defend gardens against caterpillars like corn earworm, tomato fruit worm, cabbageworm, and tent caterpillars.


The parasitic wasp has a piercing ovipositor. She lays an egg on the aphid, and the larva eats the aphid, which is not dead. When you look at an aphid colony and see perfectly round holes in the abdomens of individuals, the wasps have completed their life cycle in the body of the aphid and emerged, leaving behind an aphid husk. If the aphids are tan-colored and fat, they are being actively parasitized. Don’t spray because the parasitoids are part of the cycle.


Trichogramma wasps

Are the smallest and one of the most popular beneficial wasps. They are much smaller than the other three parasitic wasps – like a speck of dust. Females lay up to 300 eggs, usually in the eggs of the host insect.  But some also lay eggs directly into the bodies of adult scale, aphids, beetles, psyllids and caterpillars such as cutworms, hornworms, corn earworms, and leafrollers. Trichogramma wasps can be purchased in nurseries and organic growing supply stores.




Braconid wasps lay eggs in caterpillars and aphids too – check for perfect circular holes in mummified aphids or pupating wasps on hornworms.






Chalcid wasps parasitize caterpillars of several different species, while






Ichneumonid wasps specialize primarily in tree pest insects.  Chalcid, Braconid and Icneumonid wasps are much larger than Trichogramma and parasitize caterpillars directly.




To attract all these beneficials into your yard, provide habitat in the form of native nectar plants from the sunflower, mint, and carrot families – native yarrow, biscuit root, and coyote mint.  Remember, tiny mouths need tiny, shallow flowers from which to drink.