10 INTOXICATION OF HUMBLE-BEES ON CERTAIN CAPITULATE FLOWERS. 



(1) All the plants whose flowers produced this deleterious effect 

 had capitula, and in the one on which ninety per cent, of the phe- 

 nomena were observed the heads were very large. 



(2) The bees in rolling helplessly over the flower-heads became 

 most efl'ectually covered with pollen. 



(3) When the insects rolled off the plant, they soon recovered 

 their power of flight. They then flew to other plants of the same 

 species, greedily searching for the substance that had produced this 

 curious eftect upon them. Their whole behaviour showed clearly 

 that this particular honey possessed a strong attraction for them. 



(4) During the season mentioned above, the intoxication of 

 humble-bees on Ceniaurea and Scabiosa was such a common occur- 

 rence as to seem perfectly normal. 



There could be no doubt whatever as to the effectiveness of the 

 phenomenon in causing the cross-fertilization of the flowers. Both 

 on account of the large amount of pollen carried on the bodies of 

 the bees, and of the inevitable transfer of much of it to the stigmas, 

 which would be brought about by the rolling and dragging of the 

 insects over the tops of the florets, it might be said that the 

 arrangement was far more effective than many of those recognized 

 as normal. 



The natural deduction then seemed to be that particular capitu- 

 late flowers were normally cross-fertilized by the agency of insects 

 which were habitually intoxicated by the honey secreted by the 

 florets. 



Before publishing any observations on the subject, it seemed 

 desirable to secure a sufficient amount of the deleterious substance 

 for examination, so I determined to wait another season for this 

 purpose. Strange to say, however, five summers passed without 

 my being able to observe an undoubted instance of the phenomenon, 

 and, when it was observed, it was impossible to get the honey in 

 sufficient quantity for examination. My inability to repeat the 

 observation may have been due to want of opportunity : still, had 

 it been as common as it had seemed at first to be, I ought to have 

 seen it over and over again. It is true that towards the close of the 

 season and on cold days it is a very common occurrence to find bees 

 inert and helpless on flowers. When these are disturbed, they raise 

 the second pair of legs by way of protestation in the way described 

 above, but, as I never succeeded in seeing them alighting on the 

 plant and actually becoming incapable of flight, or, on the other 

 hand, regaining their power of flight when removed from the plant, 

 it seems pretty certain that they were either benumbed with cold 

 or suffering from starvation. 



On Sept. 3rd, 1893, at two o'clock in the afternoon, I was again 

 botanizing on the Orme. It was exceedingly sunny and warm, and 

 many humble-bees were busily searching the flowers of Centaurea 

 Scabiusa for honey. On a large plant of this species there were six 

 helpless bees. I remained here an hour, but failed to observe one 

 of the many bees visiting the plant actually becoming helpless, nor 

 did I see any of the helpless ones recovering so as to be able to fly 

 away. It seems then unlikely that these were intoxicated, and yet 



