WSU Extension


Parasitic Flies
Bee flies 
Tachinid flies 

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Caption: Tachinid fly (Tachinidae)
Photo by: D.G. James
Parasitic Flies : Tachinid flies
(revision date: 10/11/2018)

Tachinid flies resemble large house flies and are the most important group of parasitic flies usually targeting caterpillars. Tachinids range from ¼ to ½ inch in length and are usually dark, robust and hairy with stout bristles at the tip of their abdomen. Eggs are laid on their hosts or on the plants that their hosts use. Young larvae bore their way into their caterpillar hosts and feed on internal organs until the host dies and the larva re emerges to pupate.

Prey or Pest Targeted
  • Aphids, mealybugs, caterpillars, true bugs, beetles, grasshoppers, leafhoppers, spiders, wasps, bees, whiteflies, insect eggs
Attracting and Keeping Natural Enemies & Pollinators in Your Yard
  • Avoid regular use of synthetic, broad-spectrum pesticides. Infrequent use of certain narrow-spectrum pesticides is more compatible with some beneficials but generally the less chemical inputs there are, the greater and more diverse the beneficial insect community will be. Extensive lawns are also not conducive to attracting and retaining a diversity of beneficial insects, mites and spiders. Minimize lawn areas and maximize shrub and bush plantings. Many beneficials reside naturally in riparian and other ‘natural’ areas near to many back yards. Natural dispersion from these refuges ensures that some beneficials will visit back yards but they will not stay unless food, host and shelter resources are available. Native plants have closer affinities with native insects and therefore provide most of these resources. A garden with a good diversity of local native flora in and around back yards, will improve the abundance and diversity of local, beneficial arthropods. Native flora also provides natural overwintering sites for many beneficial insects and it is useful to leave at least a small area of native vegetation undisturbed during fall and winter.
  • Some kinds of beneficial insects (e.g. lady beetles, lacewings, predatory mites) are available for purchase from commercial suppliers. However, benefits from introducing these beneficials are usually limited and short-lived. Upon release, commercially obtained lady beetles and lacewings often disperse and may rapidly leave your backyard despite the presence of prey and suitable nectar resources. Generally, it is more effective and sustainable to create a garden habitat that will be colonized by beneficials naturally.


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Caption: Tachinid fly (Tachinidae)
Photo by: D.G. James