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. 
