The hish Aahwalist. 



August, 1915. 



NOTES, 



ZOOLOGY 



Bees and Colour Selectior. 



I have lately seen an interesting instance of the preference which bees 

 collecting honey or pollen show for flowers of a particular colour. In 

 one of the example beds of the Trinity College Botanic Gardens there 

 are two clumps of Oxalis, planted so closely that their flowers partly 

 intermingle- — O. florihimda with pink, and O. valdiviana with yellow 

 flowers. 



On July 15th both clumps were covered by a host of bees, chiefly 

 workers of Bombus hortorum and terrestris with a few Hive -bees. Although 

 I watched them for half -an -hour I saw few cases of bees collecting 

 indiscriminately from blossoms of each colour. Where such occurred, 

 it was done by the Hive -bees alone. Occasionally a Bombus collecting 

 from the yellow or pink flowers would alight on an adjoining flower of 

 different colour, only to fly off at once, apparently to the nest. 



On July i8th I captured and marked two bees, workers of B. hortorum, 

 from the yellow clump. After a lapse of twenty minutes I noticed one 

 of the marked bees on the pink clump, collecting industriously, but 

 carefully avoiding every yellow flower. Some time passed, and I was 

 leaving the spot when I suddenly noticed both my bees at work on the 

 yellow flowers, and on them alone. Both had evidently twice visited 

 the nest, subsequent to the marking, and appeared to confine their 

 attentions to a flower of uniform colour at each trip. The marking was 

 done by removing a circular patch of the upper abdominal pubescence 

 with a fine scissors. 



The rule of restricting attention to one class of flower, by colour, on 

 each working trip, though adhered to by Bombus, was not so carefully 

 followed by Apis. It may be that this protected, winter-fed, semi- 

 domesticated insect has undergone a weakening of certain primal instincts 

 which still govern its wilder brethren ; but the effect of this instinct 

 in limiting cross -fertilization was very well illustrated, at least in this 

 instance. 



One cannot generalize from a particular observation, but what I 

 noticed would seem to confirm Mr. Delap's view as to the wider choice 

 exercised by the Honey-bee {Irish Naturalist, vol xxii, p. 120), and is 

 somewhat at variance with Mr. Moffat's claim lor the superior 

 discriminating power of Apis (" Bees and Flowers," Ibid, p. 65). 



Anglesea Road, Dublin. 



H. E. ClITHBERT. 



