The pheromones of female moths have been extensively studied. Many contain blends of the isomers of a single chemical. The correct ratio of the isomers is necessary to maximize a behavioral response. In many butterflies, the male, not the female produces a scent that is used in mate recognition. Males of Pieris napi, (the green-veined white butterfly) emit the cis and trans isomers of citral: neral and geranial. For females to respond, both isomers must be emitted. A 1:1 ratio elicits the greatest response. The requirement for more than one chemical in a specific ratio enables a female to differentiate a courting male from plants or other sources of citral.
*Helena Larsdotter-Mellström,Kerstin Eriksson, Ilme Liblikas I, Christer Wiklund, Anna K. Borg-Karlson, Sören Nylin, Niklas Janz,1 and Mikael A. Carlsson. It’s All in the Mix: Blend-Specific Behavioral Response to a Sexual Pheromone in a Butterfly. Front Physiol. 2016; 7: 68.