go THE SENSES OF ANIMALS 



Dr. Harrison Matthews will be dealing with these delicate 

 structures in Part II and it is not necessary to go into their 

 complexities here. It is, however, very relevant to fieldwork 

 and experiments to refer to the factors which may affect the 

 scents given off and perceived by animals. The weather has 

 a great effect on scent : wind, quite obviously, has a bearing 

 on the transport of scents ; and humidity and temperature 

 also affect the degree of scent present and also the persistence 

 of scent on the ground, in the air, and in water. 



Though the sense of taste will be covered in the next 

 chapter but one, it must be appreciated that the two senses 

 of smell and taste are closely linked. There is much work 

 to be done by specialists in this connection, and one aspect 

 of the relationship between smell and taste about which we 

 appear to know little is where certain creatures are thought 

 to have meagre powers of scenting — birds for instance — yet 

 these same creatures appear to be able to taste well, as is 

 evidenced by their quick rejection of food which seems to be 

 unpalatable. 



It is interesting that scenting powers do not necessarily 

 increase as one goes up the ladder of animal life. It is impos- 

 sible to say with certainty that a mammal can smell better 

 than an insect, and comparisons of this kind lead us no- 

 where. It is clear, however, that an animal will have the 

 sense of smell developed to the degree necessary for it to 

 survive. Its olfactory abilities may be acute under the circum- 

 stances in which it lives, but outside those circumstances 

 this sense becomes useless. One can say that some moths 

 use smell as a means of locating a mate or a source of flower 

 nectar, but outside these uses scenting ability is not needed. 

 On the other hand, a mammal may require to use scent for 

 more diverse purposes and therefore it may seem to have 

 "better" smelling powers. But this does not mean that a 

 mammal detects scent more accurately or more delicately 

 than an insect. It is more true to say that a mammal has a 

 wider use for scenting abilities than an insect. 



The vast world of insects contains many examples of deli- 

 cate and specialized scent detection. The organs of scent are 

 found in the antennae or in the palps, and these are usually 

 referred to as chemo-tactic organs, that is to say organs which 



