The Dance of Nocturnal Moths and Blossoms

By Linda Ray

Rustic sphinx moth, Insects Unlocked*

Over eons of evolutionary time, nocturnal moths and the blossoms they seek have adapted to one another’s benefit. In many ways, this is a lesson in symbiosis at its finest.

What are some of the ways they work together? The proboscis (tongue) of the nocturnal sphinx moth (family Sphingidae) is quite lengthy, well-suited to reach the nectar-rich depths of narrow, tubular flowers that are too deep for other pollinators. When the moth’s tongue is not in use, it is rolled up, ready for future culinary delights. Moths are attracted to blossoms using their feathery antennae and keen sense of smell.

Nighttime blossoms—such as evening primrose, foxglove beardtongue, and scarlet beebalm—produce strong fragrances that can be detected by moths over great distances. What enhances the fragrance further is the plant’s ability to produce heat through a chemical process known as adaptive thermogenesis. This heat not only intensifies the fragrance but also helps release pollen and creates a warmer environment for cold-blooded insects on cool nights. In return, the plants are pollinated by their night visitors.

Nocturnal moths have extremely good vision. Their eyes capture and use very small amounts of light, making night travel possible. Some moths even have color vision which helps them distinguish between blossoms and landmarks. Plant blossoms that attract moths tend to be a color that reflects small amounts of light. 

 Trumpet honeysuckle (Lonicera sempervirens) fragrance attracts nighttime insect pollinators. Photo by Linda Ray

Being attracted to light is called positive phototaxis, and many nighttime pollinators use the light of the moon and stars. The latest research suggests they navigate by keeping their back to the light of the sky, a method called dorsal tilting. This positioning allows them to maintain a fixed angle relative to the brightest light source, a behavior known as transverse orientation.

In the last century, artificial light has created real problems for nocturnal insects. Artificial light pollution is prominent on much of the earth, specifically in human-populated areas. Because nocturnal insects are attracted to the brightest light source, they move toward the artificial light and away from flowering plants. This disruption between the insect and blossom seems to be one cause of the global decline in nocturnal insects as well as a decrease in the pollination of crops, fruits, and flowers. 

Here are a few suggestions for reducing light pollution and supporting nocturnal pollinators:

• Keep outdoor lights off unless necessary, or use warmer-colored bulbs (yellow or red).

• Use motion detectors, dimmers, or timers.

• Aim outdoor lights downward rather than upward.

• Close blinds at night when possible.

• Plant flowers that attract nighttime pollinators.

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Sources:

U.S. Fish & Wildlife Service: Dim the Lights for Pollinators and Plants of the NightNature: Moth-Plant Pollination Study

Yong, Ed. An Immense World. Random House, NY, 2022.

Lees, David C., and Zilli, Alberto. Moths: A Complete Guide to Biology and Behavior. Smithsonian Books, Washington, DC, 2024.

*This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.

 Rustic sphinx moth (Manduca rustica) with feathery antennae to capture smells and specialized superposition eyes for night vision