Larvae Fit for a Fight

Arge gracilicornis

While many sawflies display bold, showy colours on their abdomens, there are also quite a few that are more demure. Take Arge gracilicornis, a rose sawfly. In colour and appearance it resembles a fly, with its dark body and dusky wings. In common with other Arge spp. it also has quite reduced antennae which add to its fly like appearance. In its larval form, however, it is a different story. It has a translucent green body, dotted with vibrant yellow and black spots. A. gracilicornis larvae feed on the edges of rose and related plant leaves, leaving them quite exposed to predation by birds and a range of invertebrates. The spots along the body may act as a warning to predators: it has been shown that starlings (Sturnus vulgaris) avoid feeding on the larvae (1). The body of the larvae are also lined with bristles making them unpalatable. More impressively though, A. gracilicornis larvae, along with other Arge spp. larvae, produce antifeedent chemicals. Ants that bit Arge spp. larvae showed a pronounced lack of co-ordination (2). Extracts from the gut of larvae also exhibited a paralysing effect.

References:

1. Boevé and Müller, 2005. Chemoecology 15 pp. 51–58.
2. Petre et al., 2007. Journal of Insect Physiology 53 pp. 668–675