Bombycidae  

Antennae used to detect pheromones, find mates: moths
 

Highly sensitive antennae of many moths help them detect female sex pheromones thanks to many hairlike olfactory receptors.

 
  "Certain types of moth have an olfactory sensitivity that verges on the supernatural. They can detect a single molecule of the female sex hormone from miles away. Males of the saturniid, bombycid, and lasiocampid families of moth, which include luna, emperor, polyphemus, vaporer, and silk moths, have large, feathery antennae that bear the moths' hairlike olfactory receptors in great quantities (as many as 60,000 in some species). Thanks to their broad shape, the antennae come into contact with the largest possible volume of air, making them perfect scent receivers." (Shuker 2001:28)

"The females of some moths produce an odour that the males can detect with large feathery antennae. So sensitive are these organs and so characteristic and powerful is the scent, that a female has been known to summon a male from eleven kilometres away. At such a distance there must be as little as one molecule of scent in a cubic yard of air, yet it is sufficient to cause the male to fly in pursuit of its source. He needs both antennae to do this. With only one, he cannot establish direction, but with two he can judge on which side the scent is stronger and so fly steadily towards it. A female emperor moth, in a cage in a wood, transmitting a perfume undetectable to our nostrils, has attracted over a hundred huge males from the surrounding countryside within three hours." (Attenborough 1979:96)
  Learn more about this functional adaptation.