Four spot Chaser-skewered

I have not found out how this could have happened yet. Quite a few knowledgeable people have lloked at this image for me but we are still not certain. The rush it is spiked on is very soft stuff and I can be 99.9% certain that nobody would have done it where I found it, I very much doubt if another human had been there is years/ever!so no easy answer is to be found.