The Tiger Fly, Coenosia humilis
A Predator of Leafhoppers in San Joaquin Valley Grapes.
By Devin Carroll, 2013
Tiger flies are very common generalist predators in most vineyards and
orchards in the San Joaquin Valley, and probably in most areas of California and
elsewhere. They are small flies shaped like house flies.
In 1988 Dr. Eric M. Fisher of the
CDFA identified specimens I sent to him
as Coenosia humilis Meigen, with this
caveat: “Your samples key directly to this
species, but I qualify my identification as
‘probably’ because this genus is very large
and I have very few specimens available
to me for reference.” He also noted that
this species “is very widespread, occurring
in Europe and much of the U.S.”
Female tiger fly on citrus leaf.
Coenosia was formerly classified as
Anthomyiidae, but now is placed in the Muscidae, subfamily Coenosiinae.
Tiger flies, also called hunter flies, sit on surfaces such as leaves until
something flies by, then fly out in pursuit, catch the prey, and return to the original
spot. They then hold the prey underneath them, sucking out the fluids for about
10-20 minutes, depending on size of prey. With care they can be coaxed onto a
finger where they act like a falcon, returning to the finger after catching prey.
Typical prey in grapes are leafhoppers
and small dipterans such as midges, fungus
gnats, and Drosophila. I have observed
cannibalism. In apples I have seen them eat
adult moths of tentiform leafminers (ID not
certain) and adult parasites of that pest.
They have been reported to eat psocids and
aphids (Evans 1930). Other species are
known to eat whiteflies (Mateus 2012).
I once counted 54 tiger flies on five
Tiger fly eating gnat.
vines, eating 3 dipterans and 1 leafhopper.
Another time I counted 44 Coenosia on 10 vines, eating 9 dipterans and 1
leafhopper. This abundance is not unusual. Where leafhoppers are abundant
enough, they may make up the majority of prey.
Young adults of the related C. tigrina
can average five onion fly adults eaten per
day (Perron et. al 1956). Older adults eat
fewer per day.
Male tiger fly.
Tiger fly larvae live in soil where
they prey on soft-bodied creatures such
as onion maggots, fungus gnat larvae,
and earthworms. (Morris & Cloutier
1987).
Sassacus vitis spider
I would not rate tiger flies as top
stalking tiger fly.
biological control agents of leafhoppers
on a level with Anagrus parasites or Cheiracanthium spiders. But they contribute
along with lacewings and the many other predators that eat leafhoppers in
vineyards.
Citations
Evans, Alwen M. 1930. Observations on the Predacious Habits and Prey of
Coenosia humilis, MG (Anthomyiidae). Trans. Ent. Soc. Lond. 78 (2): 325-329.
Mateus, Célia. 2012. Bioecology and behaviour of Coenosia attenuata in
greenhouse vegetable crops in the Oeste region, Portugal. Bulletin of Insectology
65 (2): 257-263
Morris, Dael E., and Conrad Cloutier. 1987. Biology of the Predatory Fly
Coenosia tigrina (Fab.) (Diptera:Anthomyiidae): Reproduction, Development, and
Larval Feeding on Earthworms in the Laboratory. Can. Ent. 119:381-393.
Perron, J. P., E. J. LeRoux, and J. Lafrance. 1956. Notes on Coenosia tigrina (F.)
(Diptera: Anthomyiidae), Mainly on Habits and Rearing. Can. Ent. 88: 608-611.