So funny enough, I found a way to catch some flies pretty easy in case you ran out of them and your mantids need food pretty fast. Probably some of you already did this before but just posting it here for those who could use it. First, take your vacuum cleaner, put a sock over the top, use a stretcher to tie it around the tube and start vacuuming them up. They stick to the sock and look smushed, just turn the vacuum cleaner off, hold your fingers over the fly and pop it in the terrarium. Simple as that 
Hope this could be of use to some
Hope this could be of use to some
