House flies I wouldn't recommend, I've seen them eat s**t. If you're good at breeding bugs then go ahead, but only feed the offspring that has been on a good diet the entire life. Fruitflies you can probably... set fruit out if you have alot of them in your house. You can order them online and breed them then too. If you're looking to feed baby chams look up "bean weevil", a forumer told me about them and they look pretty good of a choice.
Get your self a piece of banana or even just any old fruit..put it in a cup...that you can cover,stick it outside...wait............You just maybe surprised!!!!!
haha ever made a bee trap out of a coke bottle? just use an empty water for fruit flies. cut the "funel" shape end off the bottle. and put a piece of fruit inside the other part than use tape to reatch the peice u cut off back on but reversed. l======< <-- flies go in this end and cant get back out D like those minow traps. than u place the container inside the cage remove the "funel" and let the flies out or you could stick a branch in and just get a few at a time out. oh yeah btw if u use banna put cotton inside under it cause as it gets old the juices will cause the flys to drowned.. i made that mistake lol