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T C Lethbridge – A Step in the Dark

Why should any sane person waste his time over a little fat round beetle, which is believed to be fond of truffles? Why does it matter if the beetle is rare or not? Very well, it doesn't matter. But something does, which is much more important. How does the beetle find a truffle buried in the earth, and how do we find beetle and truffle with a little ball on a bit of thread? [the pendulum] This is quite outside anything we have been taught. We have five senses, sight, hearing, smell, touch and taste. None of these can locate a buried object, but the pendulum can. This is on the fringe of a vast subject, which science has not yet bothered to explore.

At this stage I had not the slightest idea whether I had found the grub, the larva, of Bolboceras, or not. It is true that above the point where I found the second larva, there was a round hole of suitable diameter for Bolboceras and a little cone of sand thrown up from it similar to the heaps of soil thrown up by the bigger dung beetles. All that I really knew was that the grub and the truffle reacted to the same pendulum rate of 17 inches.

This was in itself remarkable. We had found the truffle rate from a few tiny scraps preserved in a Swiss tin of pate. But I was not bothering particularly whether I had found the right beetle or not. I was thinking more in terms of how any beetle managed to locate its food supply.

Fabre in his Social Life in the Insect World, clearly realized that insects arrived at their desired destination by following some rays which we could not appreciate.

If insect and food reacted to the same rate on the pendulum, then we might learn something of considerable interest. The obvious candidates for examination were the beetles, which flew to dung and over whom I had already spent many disgusting hours. Had dung beetles a pendulum rate and, if so, was this the same rate as that given by a cowpat? This was easy to find out. Sticken was full of cowpats and dung-beetles. To quote only a few species, Aphodius rufipes, ater, fimitarius and erraticus; Geotrupes stercoraricus and vernalis and Onthophagus vacca , aII responded to a rate of 16 inches. So did cow dung. I could examine many more, but see no reason why I should be bothered to do so.

But then something quite unexpected happened.

We found that the 17-inch rate belonged to beech nuts and beech trees as well as truffles and beetles. Perhaps this is not surprising. The dung beetles have the rate for cowpats on which they-feed and in which they go through their life cycle. Why should not Bolboceras' larva feed on beech nuts? The mycelium of the truffle grows on rotted beech nuts and the perfect insect, the imago of Bolboceras, enjoys the truffles, even the land-snail, cyclostoma elegans reacts to 17 when under beeches. It all makes sense.