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, &c., 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 



