Insects and their world 



Fig. 43. A crane-fly. 



Order Diptera, is 



slender and bare 



person with a white stick tapping his way along a street, and illustrates 

 how an insect rehes less on sight than we do, and more on touch. 



Besides being used directly for exploring the world around, the sense 

 of touch in insects plays a part in controlling balance, through reflexes, 

 as we shall see in Chapter VI. Many insects start to fly as soon as the 

 weight is taken off the feet, and it seems that the sense of touch in the 

 tarsi is directly linked to the flying control. 



Smell and Taste 

 Smell and taste are related senses, and both detect certain chemical 

 substances. Smell detects them when they are present in the air, as a 

 vapour, while taste detects Uquids or soUds when they are placed in 

 contact with the sense organ. Whether fine droplets suspended in the 

 air are smelled or tasted is a matter of opinion. 



For these olfactory senses, the insect has no special organ to corres- 

 pond to our nose or tongue, but again makes use of a number of tiny 

 mechanisms scattered over the surface of the body. These are further 

 modifications of those very versatile sensory hairs that have already 

 been used for detecting sounds and for giving the sensation of touch. 

 The cuticle has become so thin that the molecules of the chemical to be 

 deteaed can pass through it, and stimulate a bundle of nerve-endings 

 below. 



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