Chronological changes in terrestrial insect assemblages in the arid zone of Australia.

Arid and semiarid environments are characterized by highly unpredictable and 'pulsed' availability of essential biological resources. The 'boom and bust' response of many vertebrates is commonly invoked for invertebrates and especially insects. This perception of the Australian arid zone is exacerbated by the lack of long-term surveys of insects identified at high levels of taxonomic resolution. From an 18 mo continuous survey of insects in central Australia I determine the phenology of many insect taxa, and clarify which climatic variables most influenced the activity of these taxa. Total abundance and taxon richness were higher in the warmer months and lower in the cooler months. Minimum temperature, rainfall during the survey month, and rainfall during the previous month had significant effects on phenology, demonstrating that there is pronounced and predictable activity of many species in the absence of rain, although rainfall has a marked effect on the activity of some species. Other species were more active or only active in the coolest months. These findings have implications for the most productive time for surveys in the Australian arid zone, the availability of insects as prey or pollinators, and for the potential effects of climate change.