I would not make the party wait for me, so I picked the animal with me in a little container.
Back home I did the final stacking from the field captures and the final picture looked strange: The animal had obviously no head.
But when I looked into the container the animal was indeed very alive trying to find a better place. Apparently it had used the old trick of playing dead at the first handling.
Cunsulting my handbooks I identified it as the larvae of Lampyris noctiluca, the European glow-worm. It in not common in Denmark and I had never seen it before. Didn't even know it was present in my area.
The larvae are found both earlier and later in the year than the adults. Their main food is snails killed and digested by means of poisonous salvia injected via the thin and sharp claw-like mandibles.
I arranged a little scene with moist grass in my studio and took some more pictures. Since it was continually moving I had to use diffused flash. The species might be rare in our area so I did not want to kill it.
Full size on Flickr
It is surprising to see how the head and neck can be retracted or protuded like a turtle. A little black eye is visible close-up.
Full size on Flickr
The brightest glowing individuals are the adult wingless females trying to attract the flying males in midsummer. According to the litterature the males and larvae are also able to emit ligt as a warning to enimies (they are poisonous), but not as bright as the females.
I moved the box to a dark room and opened the lid. I could not see anything apart from a weak but distinct little light spot in the corner of the box. When I turned the light on it was exactly the position of the larvae's last segment.
Next day I returned the animal to its moist grassland with lots of snails. Good luck! See you next year.
Back home I opened the first picture with the stiff, headless larvae, turned the light down to simulate a summer night and enhanced the contrast a little. I am ready to believe that I can see a weak diffuse light shining from the back tip of the larvae. Or may be not?
A fascinating creature anyway.
[Edit: added links to Flickr]