Preference and avoidance behaviour of Chrysomelid beetles using olfactory sensing of potential host-tree competitors

Abstract

Chrysomelid beetles are a family of phytophagous insects which feed on nutritious young Eucalyptus leaves. Though they have been known to cause extensive damage to Eucalyptus crops, they are considered a charismatic native insect in Australia. Comparatively, the Steelblue sawfly (Perga affinis), more commonly known as “spitfires” are known to not only affect, but strip entire trees of their leaves, particularly in Eucalyptus crops. In Kosciuzsko National Park, NSW, we investigated the olfactory preferences of Chrysomelid beetles when presented with a variety of odours. We aimed to identify the attractance and avoidance behaviours of these beetles to their potential competitior, the Steelblue sawfly, using a Y-maze olfactometer. Results revealed a complex relationship between these herbivores and their host plant, whilst illuminating possible hijacking of P. affinis pheromones by Chrysomelid beetles in order to maximise their nutrition from foraging, both as adults and larvae. An increase in P. affinis population in the area could cause the Chrysomelid beetles to be outcompeted. By understanding the preference and avoidance behaviours of these beetles, we can better manage and maintain their populations into the future