Ornaments could evolve as honest indicators of fighting ability, provided they have costs that make deceptive signalling unprofitable. I tested for such costs by manipulating the size of the intrasexually selected wing spots of male rubyspot damselflies (Hetaerina americana) and monitoring survival in the field. Males with enlarged spots had higher mortality rates than both unmanipulated and sham-manipulated controls. Natural wing spot size correlated positively with longevity, which suggests that higher quality males develop larger spots.
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