98 SECRETS OF ANIMAL LIFE 



poison of toads, known as phrynin, inflames the 

 olfactory membrane if we sniff it, yet there is no 

 smell. It is certain that the world is full of scents, 

 as of sounds, to which, happily or unhappily, our 

 senses are not attuned. There is experimental 

 evidence of a highly specialized sense of smell in 

 many insects, such as hive-bees, and its practical 

 value to flower-visitors is obvious. According to a 

 recent investigator, a drone bee has 2600 olfactory 

 pores, and responds to a suddenly introduced 

 fragrance, such as oil of thyme, in 2.9 seconds; a 

 worker had 2200 pores, and responds in 3.4 seconds ; 

 and a queen has 1800 pores, and responds in 4.9 

 seconds. 



Odoriferous substances are formed in many in- 

 sects besides moths and butterflies, as every one 

 knows in the case of cockroaches and bugs, and it is 

 possible that they have primarily to do with waste- 

 products, just as the white and yellow color of 

 some butterflies is due to uric acid or derivatives 

 thereof a literal beauty for ashes. Secondarily, 

 however, the scents of insects have come to have a 

 significance in mating, and they are often confined 

 to the males. They are comparable to the musky 

 odors of musk-deer, musk-ox, and crocodile, and 

 to other scents in many male mammals and in some 

 male reptiles. The presence of scent-glands in many 

 male bats is an obviously useful adaptation to 

 crepuscular conditions; that there should be 

 practically no development of the kind in birds is 

 naturally correlated with their poor sense of smell. 



