Standing next to a clump of Nicotiana flowers on warm summer nights in Indiana, I sometimes hear the loud hum of hawkmoths. Tobacco hornworm moths fly at night and collect nectar from flowers of Nicotiana. The Nicotiana flowers are closed in the day, but open at night to attract their moth pollinators. Floral scents the emanate from the flowers attract the moths. A hawkmoth will hover next to a flower, uncurling its long proboscis and inserting it into the opening of the flower.
A group of scientists* discovered that floral scents also guide the tip of the moth proboscis after it is inserted into the flower. The flower releases floral scent next to the nectar reward and the pollen that the moth will deliver to other flowers. To observe the effect of floral scent on proboscis movement, the scientists used, floral scent was placed in a glass Y-tube to provide moths with a choice. Floral scent was released in one arm of the Y; no odor was present in the other arm. Moths probed the Y-tube with their proboscis. When the proboscis reached the Y junction, they moth could choose which arm of the Y to probe further. The moths preferred to probe the arm that contained the floral scent. Further research revealed olfactory receptors on the tip of the proboscis that responded to the floral scent.
We think of moths olfaction as being located in the antennae. However, the antennae cannot provide guidance for a proboscis inside the narrow neck of a Nicotiana flower. The floral scent receptors on the tip of the proboscis are ideally located to provide the moth with the information needed to quickly locate the nectar reward.
*Alexander Haverkamp et al. Hawkmoths evaluate scenting flowers with the tip of their proboscis. eLife 2016;5:e15039