structure often inhibits the evolution of cooperation in the snowdrift game. Nature 428. 643-646. I ielantria. II.. TolfiSki. A.. Wenseleers. 1', %Hoicks. F.LW.. 2006. Worker policing in the common wasp liespncla sultans is not aimed al Improving colony hygiene. lusectes Soc. 53. 399-402. titian:era