Phylogram showing peptide sequences of odorant receptors from Tribolium castaneum (TcOrs) and Megacyllene caryae (McOrs). Partial sequences of at least 200 amino acids are included in the tree and denoted by the suffix “PAR”. Receptors are organized into groups 1–6 defined by Engsontia et al. (2008), but including a group described only from M. caryae (7). Receptors from Groups 4–6, not present in the antennal transcriptome of M. caryae, are represented as black triangles to indicate the number of omitted receptors. Receptors of M. caryae that are sensitive to pheromone components (and the Orco) are indicated by “+”, those insensitive to components are indicated by “−”, and those that were not tested (ligands unknown) are indicated by “•”. The tree is rooted with Orco proteins from both species (McOr1, TcOr1).