Those butterfly nets sold in stores are just too small. The handles are too short, butterflies fly away too fast to catch. The rims are to small, you've really got to have good aim to catch a moving object. Make one from a large fish net with a large opening and deeper netting. Even the smaller kids can do this, with some help from a grown-up. You can use a crochet needle for the sewing, so nobody gets poked.
Fold the mesh in half and sew up the bottom and side. Wrap the top around the rim of the frame, and sew it all the way around.
Parents: I used a very light weight mesh.
I'd suggest you use a heavier weight mesh, or lace. When mine gets snagged on twigs
or branches, it rips easily. Also, the little extra weight helps to 'wrap' the net
closed when catching the butterflies.