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A Note upon the Way in which Bees settle on Flowers of 



Derris thyrsiflora, and the Injury resulting* from 



their Search for Honey. 



By I. H. Burkill. 



In the Botanic Gardens, Singapore, there is a large plant of 

 Derris thyrsiflora, Benth., climbing over a tree of CyrtopliyUum 

 fragrans, DC, near to the Director's house. Its stem has a circum- 

 ference at the base of eighty centimetres; and it ascends to nearly 

 20 metres. When in flower it is Very conspicuous, and attracts 

 enormous numbers of bees, whose hum on the flowers is heard all 

 day. Among the bees are Apis dorsata^ L., Apis indica, F., Xylo- 

 copa latipes, F. rarely, Xi aestuans, L., Anthophora zonata, L., and 

 Melipona sp. Occassionally a butterfly visits also. 



Owing to the height at which the flowers stand, it has been 

 extremely difficult to take the insects; and the list is consequently 

 imperfect. 



The flower of Derris thyrsiflora in face and in side view 

 X 2 : the standard and right ala showing the places most 

 injured by the bees. 



The flowers are white with an undefined line of green down 

 the centre of the standard. Their form is seen in the figures above. 



In all their parts oxidation develops a black pigment: and by 

 means of this it has been interesting to observe the injury which 

 visitors do to the flowers; for injury results in oxidation. 



The mechanism of the flower is tyfpically papilionaceous. 

 There is abundant honey within the stamina! tube : the approach to 

 it is by a wide opening upon either side of the free upper filament 

 allowing easy access to those insects which can force apart the 

 standard and the interlocked wings and keel sufficiently. The one 



Jour. Straits Branch E. A. Soc, No. 77, 1917. 



