Here's something I have never seen before. When I spotted two damselflies in the grass I assumed it was a mating pair but it turned out to be something more sinister.
The female was a blue-tailed damselfly (Ischnura elegans) of rufescens-obsoleta colour form. The male was a common blue damselfly (Enallagma cyathigerum). The slightly gruesome part is that the front end of the male was still alive for a while, or at least his legs were twitching. She eventually discarded the front of the body and sat eating the abdomen.
I am not sure this is true cannibalism as some definitions I found specify that the victim and the perpetrator are the same species but, if not, it's pretty close.