PARENTAL AND SEXUAL CHARACTERS 99 
and there is considerable evidence that they 
always sing for this purpose. When perform- 
ing, the males invariably take up prominent 
positions, the tops of trees, high in the air, on 
the summits of rocks, &¢., whence they may 
easily be seen from all around. Further, many 
of them sing when disturbed or frightened 
by an enemy ; a stone cast into a reed-bed or 
thicket will at once start the warblers in full 
chorus. They sing in the morning and evening 
when predatory animals are feeding. They 
sing when a hawk or weasel shows itself in 
the copse. They do not sing to their females, 
who may be out of hearing, and who take no 
notice of the song, but proceed with the affairs 
of the day, unaffected. May not this male 
character be brought into the line which many 
other male characters have been considered 
to take, namely, that its purpose is to attract 
possible enemies, so that comparatively value- 
less males may perish, rather than their valu- 
able females, or at least draw the enemy’s 
attack ? 
The instrumentation of the males of insects 
may also be, in many cases, for this purpose. 
Sound-producing males are most commonly 
found in palatable insects. 
Scent may similarly be used for female 
