O.K. Everyone's in church, I guess, or recovering from Saturday night, so I'll make my own post. Many members have been concerned about how long house fly pupae can survive in the refrigerator (about two weeks if it's not too cold (36+) and overlook the fact that adults can be maintained for between four and six weeks under the right conditions (temps around 70-80F, adequate food and humidity).
I think that Katt has posted this useful URL before:
http://www.adcham.com/html/insects/insects-fly-rearing.html
I have used it to raise houseflies and found that to be a messy and uncertain business, so now I maintain two buckets of flies with eclosure dates two weeks apart and order from SpiderPharm once a month.
A few notes on the setup on the AdCham website.
The only procedure that requires anything remotely approaching skill is cutting a hole in the bucket to take the nominal 4" PVC or ABS pipe, which must take a slightly deformed 8oz deli cup (take one to the store to check, if you are unsure). Cut out a paper template of the outer circumference of the pipe and stick it on the bucket about 4" from the bottom. Cut out the hole with a utility or Exacto knife. You will find that because of the curvature of the bucket, the pipe will fit from top to bottom but not side to side. Carefully expand the side of the hole until the pipe fits, the tighter the fit the better. Glue the pipe in place with with plenty of epoxy cement and let it cure for 24 hours. You could try an appropriate sized hole saw on a drill, but you'd have to be sure that it was the right size.
Place an 8oz cup filled with water and wood chips in the bucket, opposite the port opening Place a large pair of pantyhose (queen size"?) over the top of the bucket so that the legs are centered and outside the bucket.
Differences from the website:
You can get 6" precut pipe. That is long enough.
Cover the outside of the port with the sleeve of a black, heavy sweater (Goodwill) and be sure that it fits securely, and cement in place. Nearly done. Cut the foot off one of the panty hose legs, high enough so that you can fit an inverted 32oz cup into it. This will sit upside down on top of the bucket.
Place one 80z pot containing whatever you like to feed your flies and another containing the fly pupae (the water container is already in place) and wait. You will find that the heavy black sleeve on the port doesn't need to be secured, since the flies will not fly into the dark.
In a couple of days, you will find that the flies have emerged and all you have to do is top um the food and maintain the humidity (I introduce a vial of water through the port and top up the level in the pot) and food, and harvest a day's supply of flies.
With a little encouragement, the flies will enter the cup. Reach in through the port with a lid and close the cup. Twist off the stocking below the lid and secure it with locking forceps (Radio Shack) or a wire twist. Remove the pot, add another and release the clamp. Prepare the flies for feeding in whatever what you prefer, by chilling or capturing in individual vials, or hypnotizing them to fly into the mantis enclosures.
The advantages of this method are long life of flies from one batch of pupae, no uncertainty, ease of maintenance and relatively low escape rate.
Good luck!