All these astounding changes had come to pass through the heat and moisture of a tropical year, and under deliberate scientific calculation there was nothing unusual in the alteration. I remembered the remarkable growth of one of the laboratory bamboo shoots during the rainy season--twelve and a half feet in sixteen days, but that was a single stem like a blade of grass, whereas here the whole landscape was altered--new birds, new insects, branches, foliage, flowers, where twelve short months past, was open sky above low weeds.
In the hollow root on the beach, my band of crane-flies had danced for a thousand hours, but here was a sound which had apparently never ceased for more than a year--perhaps five thousand hours of daylight. It was a low, penetrating, abruptly reiterated beat, occurring about once every second and a half, and distinctly audible a hundred feet away. The "low bush" from which it proceeded last year, was now a respectable sapling, and the source far out of reach overhead. I discovered a roundish mass among the leaves, and the first stroke of the ax sent the rhythm up to once a second, but did not alter the timbre. A few blows and the small trunk gave way and I fled for my life. But there was no angry buzzing and I came close. After a cessation of ten or fifteen seconds the sound began again, weaker but steady. The foliage was alive with small Azteca ants, but these were tenants of several small nests near by, and at the catastrophe overran everything.
The largest structure was the smooth carton nest of a wasp, a beautiful species, pale yellowish-red with wine-colored wings. Only once did an individual make an attempt to sting and even when my head was within six inches, the wasps rested quietly on the broken combs. By careful watching, I observed that many of the insects jerked the abdomen sharply downward, butting the comb or shell of smooth paper a forceful blow, and producing a very distinct noise. I could not at first see the mass of wasps which were giving forth the major rhythm, as they were hidden deep in the nest, but the fifty-odd wasps in sight kept perfect time, or occasionally an individual skipped one or two beats, coming in regularly on every alternate or every third beat. Where they were two or three deep, the uppermost wasps struck the insects below them with their abdomens in perfect rhythm with the nest beat. For half an hour the sound continued, then died down and was not heard again. The wasps dispersed during the night and the nest was deserted.