Wasp Eating Fly
The Mediterranean Fruit Fly is a pest of fruits. Males form swarms, called “mating leks” to attract female Med Flies. A female Med Fly can find a swarm of males more readily than a single male. The mating leks are held together by pheromones, chemicals that are released by the males. The pheromone forms a cloud surrounding the swarm. When an individual male leaves the pheromone cloud, it reverses course and reenters the cloud. Pheromone not only attracts Med Flies but also attract predators such as yellow jackets.* Foraging yellow jackets will orient to male pheromone odor to locate mating leks within the canopy. The yellow jackets will swoop in and captured males that are more focused on mating than avoiding predators.
Med Fly lekking peaks around mid morning. During the afternoon, yellow jackets may switch to visual hunting for female Med Flies that are focused on laying eggs on fruit. Yellow jackets can provide some reduction in Med Fly populations but not to a level that limits damage to an acceptible level.
*Hendrichs, J.; Katsoyannos, B.I.; Wornoayporn, V.; Hendrichs, M.A. 1994. Odour-mediated foraging by yellow jacket wasps: predation on leks of pheromone-calling Mediterranean fruit fly males. Oecologia. 99: 88-94.
About jjneal
Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010).
This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog.
The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
Living With Insects Blog 
I have a question about fruit flies that I am sure you have heard a thousand times. Where do they come from? Are they in the fruit at the store? Do we bring them home or are they just small enough that they fit in through window screens? They always appear as if by magic.
Yes they are in fruit in stores. There is a new invasive, the spotted wing Drosophila that is commonly found on fruit sold commercially. The flies lay eggs and fruit, and the larvae develop, pupate and emerge in a couple of weeks as adults. The larvae and pupae are tiny and usually go unnoticed.
The Mediterranean Fruit Fly, Ceratitis capitata is a Tephritid fly.
The “Fruit Fly” of genetics fame, Drosophila melanogaster is in a different family, Drosophilidae.
They are both commonly called fruit flies, which can be confusing.