I ran my usual May course this week at Flatford Field Studies Centre on identification of freshwater invertebrates but the most unusual find was a stag beetle.

One of the course members, Mr Peter Douch (the chairman of Colchester Natural History Society) found the stag beetle on the main path from the car park. It had been attacked, possibly by a magpie, and all that was left of it was the head, with part of the first thoracic segment along with the stump of one fore leg. This was at 8am in the morning on Thursday 28th May.

When the head was brought back into the lab we were all amazed to see that the stump was moving, as if to escape, and the antennae were twitching in a fairly normal manner. When a finger was put between the 'horns' of the stag beetle it was able to grip your finger quite strongly.

Now that was very interesting in itself but, on returning from our morning's excursion to the river to sample for invertebrates, we were surprised to see the movements had not diminished at all. At intervals throughout the day our bodiless beetle continued to move it's mouthparts in a more or less constant fashion. Having finished at about 9 pm that night I don't think any of us expected to see anything more than a lifeless head by the morning.

However we were astounded the following morning to see the movement continued a full 24 hours after having been dismembered by the bird. Moreover it was still able to respond to stimulus, breathing in its direction would start the movements of the antennae and mandibles again, even though they had become somewhat more intermittent by now.

When the course finished at 2 pm on Friday 29th both the antennae and mandibles were still moving at intervals, at about 30 second intervals.
I wonder if anyone has noticed a similar phenomenon, or perhaps know how long such movements can continue for. I presume the fat body within the head contained enough reserves of energy for 36 hours of muscular movement and not having a very centralised nervous system that response to stimuli can continue. It begs the question 'What exactly is death to an insect?' and also makes me wonder if the stag beetle could still see. When we left the lab he was finally despatched - or at least we did our best to ensure this!


Adrian Chalkley