Collins New Naturalist Library. Philip Chapman

the substrate pH and other chemical characteristics. How guanobious cavernicoles respond to such changes does not seem to have been studied in any detail, but it is known that population levels of many species of guanobia increase sharply when fresh guano becomes available, and decrease when it is not.

Microclimate

      Until a few years ago, I had often wondered how the ‘terrestrial’ inhabitants of flood-prone passages and mesocavern cracks survived the regular immersions on which their livelihoods depend. It took a visit to the New Guinea highlands to reveal the secret. I was involved, with a large British expedition, in exploring the huge labyrinth of Selminum Tem – then the longest cave in the southern hemisphere. One day, while a small group of us were in the bowels of the system, the heavens opened and 10 cm of rain fell in a couple of hours. The cave streams rose by several feet in a matter of minutes, and we were lucky to get out in one piece. Two of the team were working in a young, immature network of passages deep below the main trunk of the cave and in their haste to escape the rising water, they dropped a quantity of expensive equipment. So a couple of days later, a colleague and I returned to retrieve it. The passage had obviously flooded to the roof, and the water level was still falling, amid distant gloops and gurgles. The walls and ceiling of the passage were coated with a thin layer of wet black mud, spangled here and there with fragments of soggy biscuit, washed from a packet dropped by the fleeing cavers two days previously. Several of the fragments had already attracted beetles and millipedes, and as I watched, a glistening wet millipede slowly emerged from the depths of a crack and headed across the mud in the direction of the nearest biscuit fragment. Further along the passage, millipedes of two different species appeared to be feeding on the floor of a temporary puddle – underwater. Later I watched a woodlouse doing the same thing. It seemed that the cave community here was quite amphibious; sheltering in cracks and crevices as the waters swept through their home and sallying forth to feed once the flood had passed by.