Ability for Aedes albopictus (Diptera: Culicidae) to survive at the climatic limits of its potential range in eastern...

Aedes albopictus (Skuse) is one of the most invasive mosquito species in the world and has infested islands in the Torres Strait, off the northern coast of Australia since at least 2004. This has led to fears that it may establish on the Australian mainland, including highly populated cities in southern temperate regions. To supplement theoretical projections addressing the range expansion of Ae. albopictus into Australia, laboratory-based trials were conducted to assess the performance of a Torres Strait Ae. albopictus population under a range of Australian conditions. First-instar larvae were placed in individual microcosms and maintained on a natural food resource, under average climatic conditions representing different regions of Australia's east coast. Larvae could not survive winter conditions in southern Australia. As the population performance index was >1.0 for tropical winter and summer conditions, and temperate summer conditions, populations would likely increase during these times. To test whether Ae. albopictus could overwinter during adverse conditions as eggs, we exposed cohorts to four different temperature (7, 17, 27, and 33 degrees C) and relative humidity (35, 55, and 80%) combinations for up to 3 mo. High temperatures and low humidity were most detrimental to egg survival. However, those eggs maintained under cooler climates remained viable after 3 mo, including 17% of eggs kept at 7 degrees C. Overall, this study suggests that a Torres Strait Ae. albopictus strain could proliferate all year round under northern tropical conditions and could overwinter in the egg stage before proliferating in the summer in southern temperate regions.