CONSPICUOUS FLOWERS RARELY VISITED BY INSCETS 155 



ably seldom make the attempt. After the pollen has been entirely 

 removed there is, of course, no reason why bees should continue 

 their visits. In an earlier paper I have shown that flowers fre- 

 quently visited by bees were almost entirely deserted when the 

 corollas were removed ; there is, therefore, good reason to believe 

 that the purple sepals of Clematis attract the attention of insects. 

 I next proceeded to place on a few flowers an odorless sweet 

 liquid for the purpose of ascertaining whether they would not 

 be visited by bees in large numbers. White granulated sugar 

 dissolved in equal parts of water yields an odorless and colorless 

 syrup, as is admitted by Plateau. ^ June 16 and 17 were 

 cloudy, rainy days, but the 18th was fair. At 8 o'clock a. m., a 

 small quantity of syrup of sugar was placed on three flowers. 

 No visitors were observed until 9:15, when two females of Halictus 

 craterus began feeding on the syrup ; five minutes later there was 

 a honey-bee at the syrup and a female of Halictus craterus 

 gathering pollen. Sugar syrup was now placed on a fourth flower. 

 At 10:00 o'clock there were three honey-bees and one female 

 H. craterus feeding on the syrup, a second female H. craterus 

 on a flower without syrup, and a third hovering in the air. Ten 

 minutes later a honey-bee left a flower on which there was syrup 

 and flew to two empty flowers; but, after carefully examining 

 their centers and finding nothing, it returned to the flower on 

 which it had previously been at work. The bees were compelled 

 to learn by experience which flowers contained syrup and which 

 did not. I replenished the supply of syrup from time to time 

 as it was consumed, and at 12:15 p. m., there were seven honey- 

 bees sucking on the flowers. On the morning of June 19 I 

 again put syrup of sugar on the flowers, and presently three or 

 four bees were at work. It seemed needless to continue the 

 experiment further, for the bees came from my apiary and it was 

 only a question of time and of supplying the syrup in sufficient 

 quantity to have attracted them in great numbers. During 

 the latter part of this experiment there were eighteen flowers in 

 bloom. Plateau's assumption that the flowers would not be 

 visited unless they were given an agreeable odor was shown to 

 be wholly erroneous; the addition of an odorless sweet liquid 

 secured the visits of insects in far greater numbers than were 

 observed by him. 



« Plateau, F., " Recherches experimentales," etc., p. 19. 



