Today I witnessed such an occurrence and it held a sad connotation for me.
We were walking past a tall swan plant (milkweed), a few houses along the road from our house, when I noticed Monarch butterfly wings hanging high in the plant. We pulled that section of the plant closer and discovered it to be a praying mantis holding onto the remains of a Monarch butterfly. The head and most of the abdomen had been completely eaten away.
In studying the wings I realised it was a male Monarch I had photographed mating in our garden a few days before. I recognised the location of several tears on it's wings, which I checked against my earlier photos. It was a small male with quite battered wings, suggesting it to be towards the latter time of its life. I had witnessed it mating, so arguably it had performed its life purpose.
I had watched that Monarch circling around in our garden for some weeks, sometimes twirling with another Monarch, other times supping on nectar from the flowers, other times just resting on leaves. It was a joy to watch. I'll miss it.