Green Tiger Beetle (Cicindela campestris)
Tiger by name; tiger by nature! If you are a small, ground living insect this is one sight you never want to see. This beetle may be less than half an inch long but it has the most enormous jaws.
The Green Tiger Beetle nests in holes that it makes in the ground and so loves soft sandy soil, the sort found on the Dorset heath.
It is quite common and you will generally find it on bare paths leading through the heather. That said, you don't often see them as they are small, they move quickly and readily fly, not great distances but will take to air and fly a few yards as soon as they feel your footsteps approaching.
I have been trying to photograph one for five years. In the end I found this one by a trail of Wood Ants. After tracking it for just a minute or so it snapped up an ant and stopped to eat it and despite the attentions of my camera lens it didn't budge as it munched its lunch. You may just be able to see the rear end of the unfortunate ant sticking out of its mouth.
I think these are really beautiful beetles when you see them close up like this.