My outdoor Fly culturing project

The premise for my outdoor fly-culturing project is this: I had previously raised curly-winged houseflies indoors (procured around 2002 from the United Kingdom) and, finding it to be a stinky proposition that my wife would no longer tolerate indoors, I decided to create a container that would both attract flies and allow them to reproduce outdoors. I hope this helps anyone who wishes to raise, breed or attract musca domestica (house flies).

Some factors to consider when raising houseflies are these: adequate ventilation (houseflies and their larvae require a lot of ventilation unless in a dormant state), the prevalence of pests (mites, parasitic wasps and birds), the need to keep the media adequately wet and warm, yet ventilated, the need to keep the pupation area dry and cool, the need for adult flies to have an appealing egg laying site, the need for flies to be able to access the inside of the container and my personal desire to collect additional flies that were in the container to use as feeders.

The first thing I decided to do, before creating the media, was to create the container. I decided to utilize a large detergent bucket with a lid. In order to ensure that flies could come in and out, I created a hole that fit directly with a mayonnaise jar so that I could cut a hole in the top of the mayo jar lid to screw the mayo container on and off (for capturing the excess flies). I then drilled small holes in the top of the container. These holes were drilled to allow fruit (and other small flies) to escape if trapped in the container with larger flies but not to allow house or larger flies to escape, except through the main portal. The reason I drilled holes in the top was so that I could put packaging tape on the sides of the lid. The reason why packaging tape was utilized was to ensure that mites or other ground parasites would have less of an opportunity to attack the fly larvae and pupae.

The plastic Sheet with holes - Note large hole near bottom

To keep the inside of the container moist I decided that a sheet of clear plastic was needed to place in the inside bottom (over the media). As many cookies and other confection containers are often recycled at my work I was easily able to find a sheet of plastic that would fit. The plastic sheet covers ½ to 2/3 of the bottom of container. A 1” hole was created near the bottom on the sheet where the most moisture is. The purpose of this hole is to act as an adjacent opening for the newly hatched larvae to enter the moist media from the oviposition site. Smaller holes were drilled in the clear plastic sheet to enable ventilation while still retaining moisture.



Some of the ingredients in culturing house and bluebottle flies outside.

So here is how I make this container work: The media was mixed from high protein dry dog food (Purina™ Puppy Chow) and a fiber-based product. For this fiber product I used wheat bran (found very cheaply at most feed stores). The dry dog food was crushed in the blender and mixed with wheat bran in a 1-to-1 ratio. This was put in the bottom of only one side of the rearing container. Warm water was mixed in to make a media slurry. The container was tilted to keep the wettest part of the liquid on one side. The clear plastic sheet was then put on top of the media and additional wheat bran was put on the higher side (to stay dry from the media).

Wet slurry/media on left with tissue attractant. Dry Wheat bran on right.

Then a tissue was soaked with a milk-water solution and put next to the 1” hole in the plastic sheet. A few grains of yeast were sprinkled over the 1” hole next to the oviposition site. The lid was added and packaging tape was stuck to the outside of the lid to keep crawling parasites out. The side of the lid with the mayo lid hole was positioned over the dry side (only wheat bran) and the entire container was placed outside (at a slight angle) with the only-bran side on a 1-2” object and the wet media side at ground level.

Ovipositioning of Fly eggs next to media entrance hole. - Yum! (=

After beginning this process I found that two additional modifications helped. First, large plastic screening was added to keep birds out (I found evidence of birds eating fly pupae) =( Next, putting the dry side in a more shady spot helped the larvae to seek to pupate in the dry wheat bran rather than seeking to crawl out of the container. Moisture level needed to be checked each day and this container would have to be positioned in a more covered area if this project were to be attempted in a rainy climate.

Wide rigid netting was required.

Where I keep my fly container on dry 75 degree days

So far, though I have been able to raise many flies to pupae stage (house flies and blue bottles) the majority of the flies have failed to hatch from pupae stage. I fear that I am getting the temperature and humidity wrong for pupae hatching to adults – something I will be fixing soon. Perhaps I am not waiting long enough for the pupae to hatch?

Small Fly Larvae

Large Fly Larvae

Fly Larvae that attempted to pupate in the dry wheat bran

Fly Larvae ready for refrigeration (to delay pupation)

 

In any case, this is a great way to raise flies and I do gather 6-12 large feeder flies just by screwing the mayo jar on top and tapping the sides of the container several times until the flies go up into the mayo jar. Note: Make sure to never leave the mayo jar on for too long, as this will not maintain an adequate supply of oxygen for the developing fly larvae. This container has saved me lots of time and effort and has provided me with a constant supply of flies (howbeit I still need to figure out the pupae to hatching fly stage).

Though specifically created for raising house flies, I have found that the following setup also attracts bluebottle flies as well as other large flies that enjoy the smell and ingredients contained in the medium I use in culturing houseflies outside.

 

 

Flies go in normally

And after a few taps of the container they are collected.

Capturing a few larger flies.

I keep my extra supply of adult flies I capture in a Gatorade container in the fridge with a screen lid and a tissue with sugar-water for them to feed on whilst in their dormant state. I transfer them after chilling them for exactly 1 minute in my freezer. Then when I want them I shake a few out and put them in the container where hungry mantises await.