Temperature-dependent development of the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae): a degree-day model with implications for range limits in New Zealand.

The Argentine ant, Linepithema humile, is an invasive species with the potential to cause significant economic and ecological damage in New Zealand. Using published information on rates of development, we induced parameters for a cumulative degree-day model for each life-stage of the Argentine ant.A summary model suggested that complete development, from egg to worker, requires approximately 445 degree-days above a threshold of 15.9°C. Meteorological records of air and soil temperatures indicated a number of sites in New Zealand that fulfil this minimum temperature requirement on an annual basis. Maps based on soil temperature data indicated suitable conditions as far south as Central Otago, while air temperature data predicted a more limited northerly distribution in Northland and Hawkes Bay. Additional factors, such as microclimatic variation, thermoregulatory behaviour, biotic interactions and dispersal opportunities will also be important in determining the precise range limits of the Argentine ant in New Zealand.