When I was a little boy I spent the long vacations in our ancestral house in San Fernando, Pampanga. There was a glass bowl in the living room that had lush, water plants in it. My favorite aunt changed the water everyday.

One afternoon, while sitting in a chair beside the bowl, I heard a soft, hissing sound coming from inside it, most probably an insect residing in the water plants. It went "Sst...", paused for 30 seconds, then went "Sst" again, and so on, at regular intervals. I called my aunt's attention to it. She, too, heard the sound. We never were able to determine what kind of insect it was, especially since we never saw it. We looked through the leaves, stems, and roots of the plants but found nothing. My aunt brought the bowl to the dining room sink, rinsed the plants, changed the water, and brought the bowl back to the table. We listened once more, and still, there was that sound. Whatever it was, we called it "Sst...".

I have never encountered such an insect and such a sound again. And it never occurred to me then that the sound actually might have been coming from one of the plants.