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| Luna moth, Actias luna |
While much more numerous but not as widely studied as their close cousin the butterfly, moths are a large and fascinating group of insects. Making up about 80% of the insect order known as Lepidoptera, most moths are active mainly at night, strangely attracted to light, and while some never eat, many species can live much longer than most butterflies and can even hibernate over the winter.
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| Cecropia moth, Hyalophora cecropia, caterpillar |
Like butterflies, the lifecycle of a moth is comprised of an egg, caterpillar (larvae), pupa, and adult. The length of this cycle and each of its phases varies with each species, with some species producing as many as 10 broods a year. Many moths have hairy bodies to help maintain the internal body temperature necessary for flight, and heat up their flight muscles by vibrating their wings, since they don’t have the radiant energy of the sun to assist them. Sphinx moths, whose wings beat 70 times per second, have a top speed of 50 kilometers per hour, and even more amazingly, many pupate underground! Moths range in size from the micros that have wingspans of 3-4 millimeters to the female Cecropia moth, with a record wingspan of over 130 millimeters, the largest insect in North America.
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| Cecropia moth, Hyalophora cecropia, cocoon |
Moths are positively phototactic, or automatically move toward a source of light. While the exact reason for this is unknown, interesting theories abound. Some moths are known to migrate short distances, and may use the night sky to navigate. They may use the moon as a primary reference point and have the ability to calibrate their flight paths as the moon moves across the night sky. This may help orient them, and can also explain the disorientation they seem to experience when they unexpectedly ‘catch’ or fly above a light source that they think is the moon. It’s also possible that moths look at light as an escape route mechanism, where flying up (toward the light) signifies safety, and flying down (toward the darkness) signifies danger.
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| Cecropia moth, Hyalophora cecropia |
Once they find an appealing source of light (preferring white versus yellow wavelengths), moths seem entranced by it. Like humans, moth’s eyes contain light sensors, but unlike humans their dark-adapting mechanism responds much more slowly than their light-adapting mechanism. This could mean that they may not want to leave the light since the dark renders them blind for so long, and might explain why they can be attracted to the light over & over again. Lastly, since moths are generally nocturnal creatures, they may respond to the light like they would the rising sun, and settle in for a good day’s sleep.
With so many thousands of moth species, even the largest can be difficult to identify. Clues can be gleaned from their profile or posture, vein patterns in their wings, and even the time of night that they are most active. Moths have antennae that are either feather-like or hair-like, with the male’s antennae being larger than the female’s. This is beneficial for detecting the pheromones (a chemical signal that triggers a natural response from a member of the same species) released by the females from as much as 8 kilometers away!
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| Imperial moth, Eacles imperialis |
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| Polyphemus moth, Antheraea polyphemus |
Some of our most beautiful nighttime jewels include the Cecropia, Imperial, Luna, and Polyphemus moths. These large moths, all members of the Giant Silkworm (Saturniidae) family, hold our greatest fascination. Cecropia larvae grow to about 4 inches in length, and you can often hear them as they eat. Imperial moths emerge in September/October awash in yellow & purple. The luminescent green Lunas, like all Saturniidae, are born without a mouth – they never eat or drink, as their main purpose is to reproduce. And the Polyphemus is named for the Greek Cyclops due to the large purple eyespot on each hindwing. So the next time you’re up at night, wander outside by a light and see if you can spot some of these lovely creatures!
