Moonlight Navigators: Shining a Light on Moths
Moonlight Navigators: Shining a Light on Moths
Written by Kristine Manganelli (Somerset County 4-H Coordinator)
Adult Cecropia Moth
I am excited to highlight moths in the blog because they get far less attention than their butterfly relatives. What better time to shine a light on moths, then during Moth Week? National Moth Week runs this year from July 18-26 and was created by The Friends of the East Brunswick Environmental Commission, right here in New Jersey! Moth Week celebrates the beauty and importance of our planet’s 160,000 moth species.
While many critters are winding down, moths begin to stir at dusk, the transitional period between sunset and nightfall. Most moths are nocturnal—active at night, or crepuscular—active at dusk and dawn. They are able to hide under the cover of darkness, while avoiding the heat of the sun and predators that prowl during daylight hours. There are even some moths like hummingbird moths, that are diurnal and come out during the day.
Adult Hummingbird Moth
If you’ve ever left an outside light on at night in the summer, you’ve probably noticed that moths and other insects are drawn towards the bright glow. This is a phenomenon known as positive phototaxis- a natural bodily movement in response to light. Moths are sensitive to certain wavelengths of light, especially ultraviolet light, or white light, and are less attracted to yellow light as it falls towards the other end of the color spectrum.
Just like we learned with lightning bugs, light pollution confuses moths and interrupts their instinctual reliance on the moon to navigate—a process called transverse orientation. This is similar to the way we use the north star as a directional guide. Moths keep the moon at a certain position in relation to their body to guide them. Unfortunately, the overuse of artificial light interferes with moth mating and navigation.
It is hard to tell the difference between moths and butterflies because they have so many similarities. Start by observing how they land. When butterflies land they close their wings together, but when moths land, they spread their wings apart. Also look at their antennae; a moth’s antennae are serrated or feathered, while a butterfly’s antennae are long, thin and always clubbed at the end.
Moths are important to our ecosystem as a valuable source of food for other creatures like bats and birds. Moths are considered an indicator species because they can be used to determine the health of habitats. If the population of moths changes or declines, this can indicate that there is a larger problem in the ecosystem that should be addressed.
Moths are also prolific pollinators. As most moths are active in the dark, they are especially integral to nighttime pollination. Along with bats, moths are one of the few pollinators that cover the night shift. The diurnal moth species pollinate during the day.
Adult Luna Moth
The stunning Luna Moth is worth a closer look. Luna moths are native to forested areas of North America (East of the Rockies) and can be seen in late spring and summer here in New Jersey. Like butterflies, Luna Moths undergo complete metamorphosis with a four-stage life cycle of egg, larva (caterpillar), pupa (cocoon), imago (adult). The female lays up to 200 eggs on the underside of leaves. The eggs hatch into caterpillars in about 1 week and will remain in this stage for about 1 month.
During this time, the caterpillar will eat almost constantly from the leaves of trees where they are born like walnut, birch, sweet gum, persimmon, sumac, and hickory; all of which are found in New Jersey. Afterwards the Luna Moth crawls to the ground where it will create a cocoon by weaving a dry leaf around itself in a silk coating. The leaf camouflages the cocoon among debris on the ground.
After about 3 weeks, the adult moth emerges in the morning, spending the remainder of the day drying its wings until it can fly. The adult Luna Moth lives for an average of 1 week with a sole purpose of procreation. They do not eat in the adult phase as they lack a mouth (proboscis) and digestive system. They live off of energy stored during the pupal stage.
Male and female Luna Moths look almost the same, except for their antennae. As Luna Moths are nocturnal and mate after midnight, they rely on their fluffy antennae to find mates. Male antennae are much fluffier which helps them detect pheromones or chemical trails released by females even from great distances. After mating or laying eggs, the adult Luna Moths will die.
The wingspan of adult Luna Moths can be anywhere from 3 to 7 inches across, making them one of the largest moths in North America. They protect themselves by spinning their flowing tendril-like wingtips in circles in an effort to escape predators. This disorients echolocation of bats, one of their main predators. Their green color allows them to camouflage with their surroundings, and their eyespots are designed to trick predators into thinking they are much larger in size.
Although not endangered, like many insects Luna Moth populations are slowly declining due to light pollution, irresponsible pesticide usage, and loss of habitat.
What you can do for moths:
Plant trees! Luna Moths prefer to lay their eggs in walnut, birch, sweet gum, persimmon, sumac, and hickory trees. Once the caterpillars hatch they will eat the leaves of these trees and they will provide habitat for Luna Moths until they are ready to pupate.
Plant a Moon Garden! Choose white flowers that reflect moonlight and make it easy for moths to see at night, flowers that bloom at night, and night-scented flowers. Moths are driven by their olfactory perception (sense of smell). Night-scented flowers evolved to release fragrance in the evening to attract moths to pollinate their flowers. Great options are Moonflowers, Jasmine, Wild Honeysuckle, Evening Primrose, and Night Phlox.
Keep outdoor lights off or to a minimum. Use softer tones like yellow light instead of white light.
Citizen Science: Observe moths in your yard and submit your data. Check out opportunities here:
Fun Moth Activities: http://statenislandmuseum.org/athome/wpcontent/uploads/2020/07/MothNight_DiscoveryKit_2020.pdf
Moth Coloring Book: https://docs.google.com/file/d/0B4lboeCKa0vaWHZuN1lIbmpRZzg/edit?pli=1