|Speckled Bush-cricket, Leptophyes punctatissima, ovipositing. Spring Park, 4 September 2012.|
It's a female Speckled Bush-cricket. What looks like a massive stinger on her rear end is an ovipositor, used by the insect to lay her eggs under the tough bark of an oak tree. This can't be easy. Oak bark is thick and tough, and this Bush-cricket has found a weak spot.
You are not likely to see this behaviour unless you are in the woods at night with a torch, looking carefully at tree-trunks, so not many people do see it.
A similar British insect, the Oak Bush-cricket, can also be found in North America, where it is called the Drumming Katydid.