Dear BEE-Lers, I would like to ask you for help: 1) I recall to have read about an 'instrument' to measure the quality of nectar sources available for bees. Basically, the set up was a number of vessels that contain sugar solution in different concentrations. The bees are supposed to visit only those artificial feeders which offer sugar solutions at the same or higher concentrations than the surrounding plants do (more or less, of course, flight distance and other parameters are involved too). Does anybody of you have experience with this or knows of some references? I thought I have read this in the von-Frisch book ('Tanzsprache und Orientierung ...') but could not find it again. 2) I recall as well to have read about a method of mass marking bees at the hive entrance with some colour pigments. Thought it was in 'Bee World' or 'J Apic Res'. Could please someone point me to relevant references. I searched the archives but have not been successful as yet. Thank you for your help! -- Michael Haberl Hessische Landesanstalt fuer Tierzucht, Abt. Bienenzucht Erlenstr. 9, 35274 Kirchhain, Germany, 51n 9w Tel: ++49-6422-9406-12 Fax: ++49-6422-9406-33 [log in to unmask]