Predatory and Parasitic Flies
Flies: Order Diptera
Predatory Flies - Family Syrphidae
Predatory Flies - Syrphid/Hover Flies-Syphidae/Ceciomyiidae (Predatory Midges) VERY High dispersion - greater than 1/4 mile.
Identification: Syrphid flies vary in size (1/8th to 3/4" long), but generally
mimic yellowjackets - so most are yellow and black striped. Syrphid flies have
a spurious vein on the wing that separates them from other flies.
Predatory midges are small, less than 1/8 inch, and brown, about the size of a fungus gnat. Predatory midge larvae are usually orange and not much bigger than the aphids they feed on; Syrphid larvae are larger, rich green or brown beautifully striped maggots that cause aphids to have bad dreams at night.
|Robber fly eating a Japanese beetle adult; go, Robber, go!||Smaller robberfly eating a gnat.|
Asilidae (Robber Flies): Robber flies also vary in size and some mimic bumblebees. Robber fly larvae are voracious predators of grubs and similar soft-bodied insects at or below the soil level. Robber flies will eat anything that they can successfully catch, including dragonflies! They are at the top of the insect food chain, similar to mantids in that respect.
Tricks- Hover flies - Syrphid Adults MUST HAVE POLLEN to lay eggs. Look for white, oblong eggs laid near aphid colonies - they are common there if present in an area. Pupae are shaped and sized like a teardrop - they start green and turn brown. For every fly you see, that's about 300 aphids eaten - yum. Syrphid larvae are also important predators of spider mites, small caterpillars, and we encourage their presence in broccoli through farmscaping. Since they can disperse widely, we only need small clumps of
If everyone had Umbellifera - we could have "Syrphid USA" especially good pollen plants are bridal wreath spirea, pussy willow, cilantro, dandylion, roquette, mustards, false dandylion (early season) and other high pollen producers, like corn, sudex, and sunflowers later in the season.
Parasitic flies (Tachnidae) Tachinids - High Dispersion - greater than
1/4 mile. ID - They are hairy, large flies (usually as big or bigger than houseflies)
with wings at a 45-degree angle. Identifiying characteristic is a rounded postscutellum.
These flies are commonly found in houses during late winter/early spring, emerging
from the hosts that crawled into your house in the fall prior. Tachinid flies
lay eggs on caterpillars and adult beetles and bugs. Many are specific to certain
caterpillars or bugs- e.g., Trichopoda pennipes against squash bugs; others
are generalists and will lay eggs on many types of caterpillars.
There is a specific tachinid parasite of Japanese beetle adults - Istocheta aldrichi - established in Northeastern USA. Food plants are important in keeping adult flies nearby - increase parasitization rates near food plants. Tachinids like extrafloral nectaries (Japanese knotweed-noxious, but attracts Japanese beetles and parasitic flies alike) and open-flowered plants like umbels, and yarrow.