Hydrotaea aenescens, marketed as Biofly, is a beneficial predatory fly used in biological pest management to reduce populations of nuisance flies such as house flies (Musca domestica) and lesser house flies (Fannia canicularis) in livestock environments. These predatory flies work naturally below the surface to disrupt fly breeding and help maintain cleaner, healthier animal facilities without relying on chemical insecticides.

Biofly is ideal for use in pig barns, dairy stables, and other livestock housing with semi-liquid manure pits, where fly pressure can quickly become a nuisance to animals and workers.

Here’s What They Look Like at Different Stages of Their Life:

Because H. aenescens is small and is a non-nuisance insect that spends much of its life close to manure and breeding substrates, most growers don’t directly see adults in the environment unless they go looking:

• Egg: Females lay eggs in or near moist manure or organic matter where fly larvae occur. The eggs are tiny and difficult to see without magnification.
• Larvae: The larval stage is the predatory phase. Larvae actively consume the maggots of pest flies.
• Pupae: After feeding, the larvae develop into pupae. These are typically found in organic material or manure where the larvae have eaten. Pupation is a non-feeding, transitional stage.
• Adult: Adults emerge from pupae as small predatory flies. Unlike pest flies, adult H. aenescens stay near the manure surface and do not irritate animals or people. Their behavior focuses on locating suitable sites for egg laying and sustaining reproduction.

Why Growers Love It:

• Targets house flies and lesser house flies at the larval stage.
• Adult predatory flies do not bother animals and stay near manure surfaces.
• Suitable for diverse production systems.
• Larval predation dramatically reduces development of new flies.

Timing is critical to achieving success with predatory flies. They perform best when introduced before pests reach outbreak levels.

Preventive use:

• Start releases early in the season when flies begin to appear or are expected based on past patterns.

Curative use:

• Use where fly larvae are present, especially near semi-liquid manure pits
• Multiple releases will be required if pest pressure is high and there is a lot of manure present on the farm

Environmental Conditions:

• Performs best between 20°C/68°F and 30°C/ 86°F.
• Efficacy is reduced at temperatures below 15°C/59°F and above 38°C/ 100°F.
• Suitable for pig and dairy stables

Proper release techniques ensure Hydrotaea aenescens establish quickly and begin controlling pests effectively:

1. Distribute the product: Place the contents of the Biofly bag into a specialized release station located inside the stable, out of reach of animals.
2. Placement and care: Keep release stations dry and sheltered, and place them in areas where manure and organic material accumulate to maximize larval food sources.
3. Recommended density: A typical guideline is 9,000 predatory flies per 100 m² of floor area, with releases in each compartment as needed.
4. Follow‑up releases: In curative situations or severe infestations, multiple releases, every 7–14 days often improves establishment and control
5. Avoid interference: Do not release immediately before or after broad‑spectrum insecticide applications. If treatments are needed, choose only those compatible with beneficial insects.

Tips for Selecting Rate:

• For high movement areas, high pest pressure or curative use → choose a higher rate and repeat releases, weekly or bi-weekly (every 7-14 days).
• For preventive use in low movement areas → choose a lower preventative rate, and watch for product establishment.
• Always match release strategy to animal, farm size, pest risk, and environment.

Visual checks: Because H. aenescens is small and is a non-nuisance insect that spends much of its life close to manure and breeding substrates, visual checks will be very difficult. You will mainly be watching fly activity.

Supplemental releases: If fly count remains high or increases, consider additional releases or review your IPM plan for gaps (e.g., residual pesticide effects, different fly species, etc).

Record‑keeping: Track release dates, environmental conditions, pest levels and predator observations to refine future programs.

What to Expect After Release:

• First week: Adults emerge from pupae and begin mating and laying eggs near manure and fly breeding sites.
• 2-3 weeks: Predatory larvae begin to feed on pest maggots, reducing the number of larvae that reach pupation and adulthood.
• Ongoing: Continued releases and good sanitation result in ongoing pressure on pest fly populations, with fewer adult flies over time.

Because predatory flies work biologically, control is progressive, not instant. Monitoring fly levels is the best way to track success.

• Place release stations near manure pits and high-organic substrates.
• Maintain routine releases during peak fly season.
• Combine with good manure management and drainage to reduce breeding sites.
• Monitor adult fly activity to time additional releases effectively.