SPECIAL SENSES OF INSECTS. II 



may be proved in several ways. For this reason scien- 

 tists are disposed to regard the simple eye rather as an 

 organ sensitive to differences in the amount of light falling 

 upon them. This light sense is a dermal possession of 

 many of the lower animals ; some of the minute one-celled 

 animals living in the water respond to changes in the 

 light intensity. The earthworm, with no eyes at all, is 

 sensible of the fact that it has come above ground, and 

 turns downward again. Your own skin, exposed to sun- 

 light, responds to the action of the light without any 

 volition of yours, and you say that you freckle or tan. 

 Bees sometimes know their hive by the color; whether this 

 sense plays any part in the wonderful "homing instinct" 

 of these insects is not certain, but they use this sense in 

 seeking food, as do many other animals, insomuch that 

 we say bees prefer certain colors of flowers, while flies as a 

 rule prefer other colors. It seems likely that butterflies' 

 bright colors are useful as recognition marks to guide 

 others of their kind. A clue as to the other possible uses 

 of bright markings on butterflies' wings may be found 

 in the fact that the wings of old butterflies are frayed and 

 often have pieces torn from them, as if bird enemies had 

 aimed for the wing spot instead of for some more vital 

 part. 



Smell. 



Smell is a sense highly developed among insects. 

 Among bees and ants the development of this sense seems 

 not equalled elsewhere in the animal kingdom. Who 

 has not at some time seen ants swarm in from some un- 

 known place toward the sugar jar or the plate of frosted 

 cake? It could not have been chance, for their path led 

 through many difficulties. Honey bees have been 



