Yellow crazy ants (Anoplolepis gracilipes) threaten invertebrates on many tropical islands, but little work has been done in continental ecosystems. We found 4.4-16.0 times more cruiser butterfly caterpillars were attacked in Australian rain forest sites with A. gracilipes than in native ant sites, and extrafloral nectar had little influence. , which may be more susceptible to effects of invasive species than continental ecosystems (Simberloff 1995). Only one published study has investigated effects of A. gracilipes on invertebrate communities on mainlands, and it found no significant effect of A. gracilipes on the abundance or richness of ground invertebrates (Hoffmann & Saul 2010).Butterflies are a group of invertebrates that may be particularly susceptible to invasions by A. gracilipes because their larval stages forage on plants. Larvae that forage on plants with EFN may be particularly at risk because A. gracilipes increases recruitment and aggressive behavior with increasing EFN availability (Savage & Whitney 2011). The aim of our study was to compare attack rates of a native caterpillar by the invasive A. gracilipes and native O. smaragdina. We conducted our experiments on two species of host plants and manipulated access to EFN on one of them. We addressed two questions: (1) are attack rates of caterpillars by A. gracilipes higher than by O. smaragdina? And (2) how does availability of EFN influence attack rates by the invasive and native ant species?We conducted our study with the native cruiser butterfly, Vindula arsinoe (Nymphalidae), an excellent proxy for many threatened butterfly species in the Wet Tropics. It oviposits in clusters, its instars have spines, and it does not sequester phytotoxins. Its preference for lowland rain forest and vine thickets (Braby 2009) overlaps with habitat invaded by A. gracilipes. Vindula arsinoe oviposits and develops on the introduced weedy vine, Passiflora foetida and the native vine, Adenia heterophylla (both Passifloraceae). Passiflora foetida has multiple minuscule extrafloral nectaries on its leaf margins, and A. heterophylla has two prominent extrafloral nectaries at the base of the petiole and underside of