Muscidifurax raptor and M. raptorellus

Biocontrol Agent

Muscidifurax raptor and Muscidifurax raptorellus are parasitoid wasps that search and find fly pupae in manure or decomposing moist organic matter often found near barns. They are effective at controlling house flies and stable flies in and around livestock facilities when used as part of an Integrated Pest Management program.

Common Names


Relative effectiveness

When combined with other IPM tactics, these two parasitoids have been shown to control 35 to 80% of house flies and stable flies on farms.

Where to use

Release around barns and animal confinement areas that have house fly or stable fly issues, focusing on areas where immature flies are developing.


About Muscidifurax raptor and M. raptorellus

Muscidifurax raptor and Muscidifurax raptorellus are parasitoid wasps that search and find fly pupae in manure or decomposing moist organic matter often found near barns. They are effective at controlling house flies and stable flies in and around livestock facilities when used under an IPM program. Using its ovipositor the parasitoids will pierce the pupa, first killing the fly, then laying its eggs. Muscidifurax raptor lay a single egg, while M. raptorellus lay up to eight eggs in each pupa. The parasitoid eggs will hatch, and the larvae will feed on the living, but paralyzed, fly pupa inside the fly puparium, eventually killing it.

  • Native/Non-native: Native
  • Established: Yes


The wasp is very small and purple-black. It stings only fly pupae and never humans. The wasp is 1 to 3 mm in length

  1. Fly eggs are laid in undisturbed, moist, rotting organic matter
  2. Fly eggs hatch into maggots, which develop through 3 instars
  3. Fly maggots pupate
  1. Parasitoid adult female lays an egg into a fly pupa
  2. The parasitoid egg hatches into a larva that feeds on the developing fly inside the puparium
  1. After the parasitoid pupates it will emerge as an adult
  2. The adult female parasitoid will then find another pupa to parasitize

How to Use Muscidifurax raptor & M. raptorellus

Biocontrol category: Augmentative - must be released/applied repeatedly

When to use: Release parasitoids weekly from May through September. Normally when a farmer purchases a plan, they will receive parasitoids in the mail weekly for release.

Rate: For dairies, Cornell University recommends weekly releases of 200 parasitoids per cow and 1,000 parasitoids per calf.
Rate of release for parasitoid wasps varies by livestock type and by the company producing the parasitoids. In the northeast U.S., we recommend mixes of M. raptor and M. raptorellus. These two parasitoids occur naturally in the northeast U.S. and are very effective at controlling stable flies and house flies. Other mixes are not as effective as M. raptor and M. raptorellus in this region.  

Pest stage: Pupa

Mode of action: Parasitoid 

Conservation: Avoid using residual insecticides to control house flies and stable flies in and around barns.  These types of insecticides are detrimental to parasitoids that help control these flies. Use an insecticide only when all other IPM tactics have been employed to control the flies. If an insecticide is needed insect growth regulators are a better option because they are more compatible with the parasitoids. Any time you use a pesticide, you must read and follow the label directions and comply with all applicable laws and regulations related to pesticide use. Also be sure that any pesticide used is approved for use in your country and state/province.

Risk: These parasitoid wasps only harm the target pest.

Commercially available: Yes

Pests Targeted by Muscidifurax raptor and M. raptorellus

Muscidifurax raptor and Muscidifurax raptorellus are parasitoid wasps that lay their eggs only in pupae of stable and house flies.

Four stable flies stuck on fly paper

Stable flies are gray and 5-7 mm long. Notice the mouthpart that protrudes from under the head, straight out. It is used to pierce the skin of an animal and feed on its blood.

stable flies resting and feeding on the legs of a cow on pasture

Stable flies on the legs of a cow. Stable flies preferentially feed on the lower legs of animals.

fly with a blob of liquid at it's mouth

House flies are also parasitized by Muscidifurax wasps.


Ken Wise
Senior Extension Associate, New York State Integrated Pest Management

Phillip Kaufman
Entomology Department, Texas A&M University

Date: May 9, 2023

  • Zchori-Fein, E., Geden, C.J., Rutz, D.A. 1992. Microsporidioses of Muscidifurax raptor (Hymenoptera: Pteromalidae) and other pteromalid parasitoids of muscoid flies, Journal of Invertebrate Pathology, Volume 60, Issue 3, Pages 292-298, ISSN 0022-2011,
  • Machtinger, E.T., Geden, C.J., Kaufman, P.E., House, A.M. 2015. Use of pupal parasitoids as biological control agents of filth flies on equine facilities, Journal of Integrated Pest Management, Volume 6, Issue 1, 16,
  • Gibson, G. & Floate, K.D. 2004. Filth fly parasitoids on dairy farms in Ontario and Quebec, Canada. Canadian Entomologist, Volume 136, 407-417. 10.4039/N03-006.
  • Smith, L. & Rutz, D.A. 1991. Relationship of microhabitat to incidence of house fly (Diptera: Muscidae) immatures and their parasitoids at dairy farms in central New York, Environmental Entomology, Volume 20, Issue 2, 1 Pages 669–674,
  • de Pedro, L., Tormos, J., Guzmán, A.M., Peris, B., Beitia, F. 2020. Quality parameters and adaptation of Muscidifurax raptorellus (Hymenoptera: Pteromalidae) against dipteran pests harmful to livestock and cultivated plants, International Journal of Pest Management, 66:4, 311-318, DOI: 10.1080/09670874.2019.1646943
  • Tucker, N.S.G. & Kaufman, P.E. 2016, A parasitoid Muscidifurax raptor Girault & Sanders (Insecta: Hymenoptera: Pteromalidae) University of Florida, Institute of Food and Agricultural Sciences, document #EENY657. 
  • Kaufman, P.E., Strong, C., Waldron, J.K., Donald A. Rutz. 2012. Individual and combined releases of Muscidifurax raptor and M. raptorellus (Hymenoptera: Pteromalidae) as a biological control tactic targeting house flies in dairy calf facilities, Journal of Medical Entomology, Volume 49, Issue 5, Pages 1059–1066,
  • Xiong, X., Kelkar, Y.D., Geden, C.J., Zhang, C., Wang, Y., Jongepier, E., Martinson, E.O., Verhulst, E.C., Gadau, J., Werren, J.H., Wang, X. 2021. Long-read assembly and annotation of the parasitoid wasp Muscidifurax raptorellus, a biological control agent for filth flies. Frontiers in Genetics. 12. 10.3389/fgene.2021.748135.
  • Rutz, D.A. & Waldron, J.K. 2016. Integrated Pest Management Guide for Organic Dairies. NYS IPM and Cornell University.
portrait of Ken Wise
Ken Wise

Senior Extension Associate

NYS Integrated Pest Management

Ken Wise