got mine at lowes in the garden section. the key is to let em eat whenever they want to. i work at a convenience store part time so flies are easy to come by. it looks like the pitcher plant already got four, and one of the flytraps is still gnawing on a mosquito i gave it two days ago.
basically, if you don't feed them, you just have to make sure the soil is good and healthy for them to draw all the nutrients out of. they mainly eat bugs to support life in harsher soil conditions.
not sure how big these things get, but i left for school this morning and everything was fine. i come back this afternoon to find a little sprout at the base about 2mm big. this evening i'm looking at it and its already tripled in size. fast little things.
as for my war on bugs, i had another thread about the interesting ways i killed the bastards.