FLY-FLOWERS 



fore darting down to suck nectar or eat i)ollen, thought that the 

 bright-yellow coloration must afford these flies an a\sthetic 

 pleasure. But more recently Plateau has shown that this is 

 merely a habit of flight, and that the hover-flies jioise on the 

 wing in the same way before green leaves, green flowers, green 

 fruits, and green and brown stems, or even before a cane, or 

 a marble, or the human finger. When a finger was gently inter- 

 posed between a fly and a flower, the fly remained in a fixed 

 attitude as before and, when the finger was slowly moved away, 

 followed it. 



Many syrphid flies closely resemble bees and wasps, and can 

 be distinguished from them with diflSculty when on the wing. 

 Field-collectors occasionally catch them and send them away as 

 wasps. By some naturalists this similarity of form and flight 

 is regarded as a case of protective resemblance, by others as 

 an accidental convergence in likeness.* 



No one can long observe flowers without meeting with the 

 bee-flies {Bomhyliidw), which both when flying and at rest are 

 often mistaken for bees. They feed on nectar, but not on 

 pollen. The species of Bomhylius are densely clothed with 

 silky hair and both in movement and appearance suggest 

 small moths. The long proboscis points directly forward, and 



* An amusing illustration recently occurred in the experience of the writer 

 showing how easily certain flies may be mistaken for honey-bees. A prominent 

 local official, accustomed to observe carefully, told me how his wife had called 

 his attention to the presence of many bees on a window of a shed chamber. 

 He related how after putting on an overcoat and protecting his face and hands, 

 he had finally driven them outdoors. 



"Now," he inquired, "how did they get there?" 



"They were not bees at all," I replied, "but flies. If you will examine them 

 carefully you will find that they have only one pair of wings." 



Naturally he was nuicli astonished at this statement; but some days later 

 he brought me two of the insects in a bottle. They proved to be, as I had 

 expected, syrphid flies belonging to the species Eristalis tenax, often found on 

 flowers. 



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