1. Centre for Ecology and Conservation; Biosciences, College of Life & Environmental Sciences; University of Exeter; Cornwall Campus Penryn Cornwall TR10 9EZ UK
2. School of Integrative Biology; University of Illinois; Urbana, 505 South Goodwin Avenue Urbana IL 61801 USA
3. Howard Hughes Medical Institute; Section of Integrative Biology; University of Texas at Austin; One University Station C0930 Austin Texas 78712 USA
4. Laboratory of Apiculture and Social Insects; School of Life Sciences; University of Sussex; Falmer Brighton BN1 9QG UK