David Stern is investigating two problems. The first is how behavior evolves. To address this, Stern and his team identify genes that cause behavior differences between fruit fly species and then determine how these genetic changes alter neuronal functions, resulting in new behaviors. The second problem is how insects hijack plant development to induce plant galls. The Stern lab has discovered that aphids inject a novel family of BICYCLE proteins that appear to contribute to gall development. The team is studying many aspects of this problem, with a focus on how BICYCLE proteins alter plant cell biology.