Darwin's Theory of Sexual Selection 189 
other. “Hence we cannot suppose that they have been 
transferred from the male to the female, as appears to have 
been the case with the secondary sexual characters of many 
other animals. They must have been independently devel- 
oped in the two sexes, which no doubt mutually call to each 
other during the season of love.” 
Some beetles also possess rasping organs in different parts 
of the body, but they cannot produce much noise by this 
means. 
“We thus see that in the different coleopterous families 
the stridulating organs are wonderfully diversified in position, 
but not much in structure. Within the same family some 
species are provided with these organs, and others are desti- 
tute of them. This diversity is intelligible, if we suppose 
that originally various beetles made a shuffling or hissing 
noise by the rubbing together of any hard and rough parts 
of their bodies, which happened to be in contact; and that 
from the noise thus produced being in some way useful, the 
rough surfaces were gradually developed into regular stridu- 
lating organs. Some beetles as they move, now produce, 
either intentionally or unintentionally, a shuffling noise, with- 
out possessing any proper organs for the purpose.” 
Darwin says that he expected from analogy to find in this 
group also differences in the sexes, but none such were found, 
although in some cases the males alone possess certain char- 
acters or have them more highly developed. 
It is important not to forget, when considering all questions 
connected with sexual selection, that in order for the result 
to be successful it is not only necessary that the female 
respond to the noises and music of the other sex, but that 
she choose the suitor that makes the greatest, or the most 
pleasing, noise. If the stridulating organs are only used by 
the animals in finding each other, then the case might be 
considered as coming under the head of natural selection. 
If this be granted, then it may be claimed, and apparently 
