Many assume that butterflies are out and about during the day while moths float around bright lights at night, making them nocturnal. But this is not necessarily the case because most of us have seen moths flying around in daylight hours. So it seems that not all species of moths are nocturnal, which begs the question: are moths nocturnal or diurnal? This article explores the sleep behavior of these insects to understand whether moths are nocturnal or diurnal.
Some Moths Are Nocturnal, While Some Are Diurnal
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Many moth species are nocturnal, and this is an evolutionary adaptation. Most of the moth’s predators are diurnal animals that can easily spot and catch them during the day. Moths are also generally darker in color, making it safer for them to sleep during the day and be active at night. However, some moths are diurnal or crepuscular, another evolutionary adaptation because their nighttime conditions were not favorable to their survival.
Do Moths Sleep?
Moths do sleep, but not as we do. It is difficult to tell when a moth is sleeping as they do not have eyelids that can close when they sleep. Moths enter a state of torpor to rest. Torpor is a resting state where the insect slows its brain function, metabolism, and heart rate.
They do this to conserve energy but are not entirely unconscious. While moths rest, they are sluggish but will move as their reflexes are still active but delayed. When moths are in a torpor state, they wake up if there are strong stimuli like loud noises or movements in their surroundings.
Moths sleep in areas where they feel safe and where they have protection. They do not build shelters or nests but rather find cover to rest. Moths sleep in spaces with minimal light, like bushes, under tree branches, in cracks of logs or stone, and sometimes in or under your home’s furniture.
A Study Found That Not All Moths Are Nocturnal
A study published in Organisms Diversity and Evolution by the Florida Museum of Natural History found that there are diurnal moth species. The study also found that there are species of butterflies that are nocturnal. This study discovered outliers, diurnal moths, and close to 50 shifts in the moth’s evolutionary history where they switched from nocturnal to diurnal.
Researchers also discovered that the earliest ancestor of moths and butterflies was diurnal and not nocturnal, as previously thought.
Moths belong to the group Lepidoptera and butterflies also form part of this group. This study learned that 75% and 85% of these insects are nocturnal, and 15% to 25% are diurnal. Examples of diurnal moths are species of silk moths, tiger moths, and borer moths. Silk moths have large, brightly colored wings similar to that of butterflies. Tiger and borer moths mimic bees as a defense mechanism.
Another study outcome found that moths living in colder areas are often diurnal because the nighttime temperatures are too cold for movement. But these insects are adaptable and can switch from nocturnal to diurnal if their environment is unfavorable during the nighttime.
Moths Have Adapted To Being Nocturnal
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People often want to know how these insects can see in the dark. Moths navigate at night following light sources or the earth’s magnetic field. When flying at night, moths position themselves and fly on a fixed angle relative to light sources, like the moon or artificial light. If there are no light sources in the area, they will use geomagnetic signals created by the earth’s magnetic field.
The reason moths are attracted to light is not fully known, but scientists have a few ideas. Light sources, like candles, emit specific wavelengths which attract moths. One hypothesis is that these wavelengths are similar to a female moth’s pheromones, which attract male moths.
Moths may also find artificial ultraviolet light attractive as they interpret it as a potential food source. Some night-blooming flowers reflect ultraviolet light, and moths may feed on these flowers.
Nocturnal Moth Vision
Besides other research regarding ultraviolet light, scientists discovered similar information about moth vision. Unlike many diurnal butterflies, the hawk moth is nocturnal. Scientists studied this nocturnal hawk moth and found that they were drawn to pale-colored flowers at night. This attraction is driven by the fact that these moths have eyes with three visual pigments. These pigments pick up ultraviolet, blue, and green wavelengths.
Due to the density and distribution of these pigments in the moth’s eye retinula, the blue pigment seems to be the most important. This importance is due to its positioning, which means that its blue photoreceptors immediately identify white flower images, which are food sources. Not all moth vision works the same, but this example indicates how the hawk moth’s nocturnal vision works.
Moths Are Most Active Between 11 P.M. and 1 A.M.
A study titled “The Hourly Distribution Of Moth Species Caught By A Light-Trap” found that most moths are active from midnight to 1 a.m. Researchers set light traps between 1976 and 1979 at night for a total of 57 nights. The study observed the peak activity time of moths to find when they are most harmful to crops.
While the study revealed almost no moth activity before 7 p.m. However, the later part of the night and early morning hours tell a different story. Researchers found that the gypsy moth was the most active between 11 p.m. and 1 a.m. The black arches moth was busiest between 3 a.m. and 5 a.m., followed by the rosy gypsy moth, active from 1 a.m. to 3 a.m.
Additionally, the study demonstrated that male pine moths were drawn to the light later in the night. In contrast, the females were more active in the earlier parts of the night between 10 p.m. and 11 p.m. This study clearly indicates that there are many nocturnal moth species, all with varying behaviors.
Certain Factors Influence a Moth’s Circadian Rhythm
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A circadian rhythm comprises the physical, mental, and behavioral changes within a 24-hour cycle. Components of the circadian rhythm are sleep and activity. Factors that can influence the moth’s sleep length, movement, and circadian rhythm in general are:
Light Settings
A day’s length of light and dark phases will influence the diurnal or nocturnal moth’s activity and sleep patterns. And as the seasons change, the day length will vary. When this happens, some moths will be more active later than earlier in the evening.
Day length at the equator is roughly 12 hours, regardless of the season. Still, the day length in the northern hemisphere is longer in the summer months and shorter in the winter months. Because of this, moths in the northern hemisphere are active earlier at night, while moths at the equator are active later at night.
Temperature
In colder areas, nocturnal moths will be more active earlier at night. As the evening progresses, the temperature drops. It may become so icy that the moth cannot fly anymore, so its activity will decrease. In warmer temperatures, nocturnal moths will be more active later at night. The temperature will drop as the night progresses. These moths will be busy in the middle of the night when the temperature is at its lowest.
Nocturnal vs. Diurnal: What’s The Difference?
Navigate to Nocturnal vs. Diurnal: What’s The Difference? for further information about the nocturnal and diurnal phenomenon in various living creatures.
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