Rain seldom falls in the extremely arid Namib Desert in Namibia, but when a certain amount falls, it causes seeds to germinate, grass to grow and seed, dry, and turn to litter that gradually decomposes over the years. It is thought that such periodic flushes and gradual decay are fundamental to the functioning of the animal populations of deserts. This notion was tested with litter-consuming darkling beetles, of which many species occur in the Namib. Beetles were trapped in buckets buried at ground level, identified, counted, and released. The numbers of most species changed with the quantity of litter, but some mainly fed on green grass and disappeared when this dried, while other species depended on the availability of moisture during winter. Several species required unusually heavy rainfalls to gradually increase their populations, while others the opposite, declining when wet, thriving when dry. All 26 beetle species experienced periods when their numbers were extremely low, but all had the capacity for a few remaining individuals to repopulate the area in good times. The remarkably different relationships of these beetles to common resources, litter, and moisture, explain how so many species can exist side by side in such a dry environment. Keywords: tenebrionidae, darkling beetle, long term ecological research, population signature, irruption, population crash, rainfall, nonrainfall moisture, detritivore, species diversity.