Not a problem. It is likely mantids encounter these in the wild and they know what they can't eat. I find all kinds of things during the summer that I feed to mine. They eat all but a few.
Let us know how love bugs work, I don't currently have any mantids to try them on, but I'm sure I speak for all of us who live in Florida when I say, it would be great ot finally have a use for those love bugs.
If you look on plants in flower suck as willow herb and thistle you will find many colourfull insects similar to that, all very popular to flower mimicing species