The cecropia moth (Hyalophora cecropia Linnaeus) is among the most spectacular of the North American Lepidoptera. It is a member of the Saturniidae, a family of moths prized by collectors and nature lovers alike for their large size and extremely showy appearance.
Adults are occasionally seen attracted to lights during spring and early summer, a common habit of many moths. It is unclear exactly why these insects visit lights, although a number of theories exist. One such theory posits that artificial lights interfere with the moths' internal navigational equipment. Moths, and indeed many other night-flying insects, use light from the moon to find their way in the dark of night.
Since the moon is effectively at optical infinity, its distant rays enter the moth's eye in parallel, making it an extremely useful navigational tool. A moth is confused as it approaches an artificial point source of light, such as a street lamp, and may often fly in circles in a constant attempt to maintain a direct flight path.
Low population density can be a problem when looking for love, so male cecropia moths must rely on powerful senses to sniff out a female's pheromones — which he can detect from more than a mile away. Unfortunately for him, however, some bolas spiders can mimic the pheromones of a female cecropia moth, thus luring unsuspecting suitors into their clutches.
Cecropias are most likely to be found in places where forested and open areas meet. With their variety of host trees, cecropias occur nearly anywhere in our state. Maples, for example, grow in parks and backyards yet also constitute a large part of our state's natural forests. Willows predominate near water, so cecropias can be found near water, too. This nocturnal species is attracted to lights at night. In some regions, numbers are declining due to habitat loss, pesticides, and more.
Larvae feed on more than 20 species of Missouri trees and shrubs, notably various maples (including box elder), willows, cherries, plums, apples, dogwoods, and lilacs. As with other giant silk moths, the mouthparts of the adults are small or absent; the adults live for only a few weeks without feeding, relying on food consumed and stored when they were caterpillars.
Adults fly from early April through June; each moth only lives for about two weeks as an adult. They are nocturnal and in the hours before sunrise emit scents to "call" to potential mates. Eggs are deposited in rows on the leaves of host plants. The eggs hatch in about 2 weeks, and at first, the larvae feed in groups. As the caterpillars grow larger, they disperse and feed as individuals. The cocoons are brownish-gray and are attached by silk along their whole length to a twig in some sheltered, inconspicuous place. Although there is only one brood in our state, the adults emerge over a long period of time and can be found from April through June. This moth overwinters in the pupal stage.
Butterfly and moth collecting is a hobby that many people enjoy, and the cecropia moth is the "jewel" of many collections. Many more people take just as much pleasure out of spying a live moth resting on a backyard tree. This is one of the giant silkworm moths that may be declining in parts of its range because of parasitism of a tachnid fly that was introduced to battle the invasive, destructive, nonnative gypsy moth.
In 1956, researchers reported a major breakthrough in their understanding of insect metamorphosis: they had isolated a hormone that, when it's being produced in large enough quantities, permits a caterpillar to keep growing and repeatedly molting into larger caterpillars ― but when the insect's body stops producing the hormone, it molts into a winged, sexually mature adult. The hormone is now called "juvenile hormone" or JH. The initial 1956 discovery was made using larvae of a cecropia moth.
The name: Cecrops was an Athenian king in Greek mythology. Another Missouri butterfly, the red-banded hairstreak's scientific name also comes from this mythological figure.
The thousands of different caterpillar species that graze on tree leaves perform a natural pruning service. The adults provide a sizeable meal for their predators. Cecropia numbers are also kept in check by several parasite species. The pupae are eaten by squirrels.