Variability of larval identification characters of exotic Aedes albopictus (Skuse) intercepted in Darwin, Northern Territory.

There is no morphological identification key to satisfactorily distinguish between the larvae of Aedes (Stegomyia) species with special consideration to endemic and exotic species in Australia. Difficulty in differentiation between exotic Aedes (Stegomyia) albopictus (Skuse) and Aedes (Stegomyia) scutellaris Walker has been described previously. Aedes (Stegomyia) larvae were collected during an interception from an overseas vessel in Darwin, Northern Territory, and link bred. The adults were identified as Ae. albopictus. The larval skins and larvae were used to describe the variation in hair features of larval segment VII that are used to identify Ae. albopictus. The median hair number of hair 1-VII was three, whereas the description in Huang's identification key states four. The median of hair 2-VII was one, confirming Huang. However, the variability was higher than described by Huang and nearly half of the specimens showed different hair numbers on both sides. Individual specimens are therefore not clearly distinguished from other members of the Aedes (Stegomyia) scutellaris group. This paper also describes the detection, elimination and surveillance procedures following the interception. These were successful in preventing the establishment of exotic Ae. albopictus in the Northern Territory following the interception.