For years, the Kalahari Desert can appear to be one of the most barren wastelands on earth. But its swirling hot sands hold unseen treasure - a swarming superabundance of life, brought forth by a brief season of sudden, unpredictable storms. Butterflies, termites and locusts burst forth in staggering numbers. Millions of quelea birds swirl in the sky like smoke. Most impressive is the giant bullfrog - the size of a dinner plate with a voice to match, this amphibian waits out the dry years entombed deep underground