CONSPICUOUS FLOWERS RARELY VISITED BY INSECTS 161 



rose, violet, or purple flowers."" Plateau, however, observed 

 visits by many bumblebees, and species of Diptera belonging to 

 the genera Eristalis and Syrphus. 



Plateau employed in his first experience a large group of Petu- 

 nias, surrounded by other plants, as Tagetes paiula and Scabiosa 

 atropurpurea, attractive to bumblebees, flies and butterflies; 

 while among the Petunias there was a single stalk of Borago 

 officinalis which alone was visited by honey-bees. On a clear 

 but cool August morning, at 9:30 o'clock, he introduced the 

 odoriferous juice of cooked cherries into six flowers near the 

 stalk of borage. At 3:30 p. m., of the same day, the honey-bees 

 discovered the cherry juice and entirely abandoned the borage 

 flowers for the Petunias. During an hour there were fourteen 

 arrivals, each individual visiting many of the garnished flowers, 

 and rarely a few of the empty flowers. Essentially similar 

 results were obtained in Plateau's other observations on Petunias. 



The two common species of Petunia endemic to South America 

 have long narrow tubes, are strongly scented in the evening, 

 and are either adapted to crepuscular Lepidoptera or are orni- 

 thophilous ; in either case we should not expect to find honey-bees 

 among their legitimate pollinators. The hybrid forms of cul- 

 tivation, moreover, are destitute of nectar; and even if it were 

 present the throat of the corolla is so obstructed by the filaments 

 and style that it would be inaccessible to them. Plateau asserted 

 that an odoriferous syrup was required to attract visits by honey- 

 bees, but it can readily be shown that the presence of an odorless, 

 sweet liquid will render their visits very numerous. A medium 

 sized group of single-flowered Petunias of various colors was sel- 

 ected for my observations. 



On July 31, 1913, there were only two flowers in bloom, into 

 both of which I introduced sugar syrup. A bumblebee inspected 

 both flowers but overlooked the syrup. On the 2nd there were 

 two fully expanded flowers, and one which had wilted and 

 closed. A honey-bee examined all three, and remained a long 

 time in one of the open flowers. As the sugar syrup had evap- 

 orated, the supply was renewed. The honey-bee returned and 

 thirty minutes later was still visiting the flowers. On the follow- 

 ing day a female Bombus consimilis was a visitor. 



2' Plateau, F., " Recherches experimentales, etc." Mem. de V Acad. roy. de Bel- 

 giqae, 2me ser., 2:46, 1910. 



