Dear Frances Thanks for your reply. Yes I've been surprised by the apparent lack of the calculation. I've been able to establish a maximal proportion of around 0.18 by using the usual statements about length of life as a forager and the ususal onset of foraging, but this seems far too low to my co-worker who is a beekeeper. If I double the lifespan of the forager and set a comparatively early onset of foraging it comes out at about 0.34. I'd appreciate the reference to your thesis and a copy of the abstract, if you dont mind me quoting it in a review of honey bee impacts on protected natural areas in New Zealand. I'm curious. Are you the Ratneiks who provided a chapter of selection at the colonising front of African Bee invasions in Marla Spivaks book? If so, congratulations! I think it isa very important contribution to invasion biology in general. Thanks for your reply, Cheers Henrik ***** Please note new e-mail address ***** Dr. Henrik Moller Co-Director, Diploma in Wildlife Management Zoology Department Univeristy of Otago Po Box 56 Dunedin New Zealand Ph: 64-3-479-7998 Fax: 64-3-479-7584