Actias Luna
(Luna Moth)

History:

Also known as the moon moth this is the only green North American Saturniidae with a wingspread of up to 5 inches. The first time I ever saw this species was when I was 10. I was walking down the road picking up hazel nuts when I found my first luna cocoon. At the time I didn’t know what it would turn into, only that whatever it was would be large. I anxiously waiting for spring to come and when the moth emerged I could hardly believe my eyes. It looked like something from a fairytale. I had seen the tails on swallowtail butterflies, but the hind wings of this moth were fantastically long. The pure white body with the rich purple band and soft luminescent green added to the effect. To this day this species has enthralled me and is my top species I rear. Luna are the most recognized species by the general public. In part it is most likely due to its size, but also the striking color and shape. It has been featured on commercials for Lunesta and weird hybrid butterfly/luna images are frequently used. This species is wide ranging as far west as California and south to Florida. This species is bivoltine in most of its northern range and multivoltine in its most western and southern ranges with adults on the wing nearly every moth of the year. They appear to favor areas composed of mature hardwoods and semi mature forests.

Reproduction:

Adult moths lack functional mouthparts or digestive system and therefore they live only for about two weeks. This strategy seems odd as many other species of moths and butterflies feed throughout the period they are adults, but allow me to break down the evolutionary advantages that allow them to do this. The female moth emerges from its cocoon with fully developed ova which allows it to be ready to receive sperm from a male and begin depositing eggs the same night that it hatches. Male moths emerge with large feathery antennae that allow them to detect female pheromones up to a mile away. Males cover long distances flying in a zigzag pattern until pheromone particles have been detected. Females begin “calling” around 10:00 p.m. and continue till dawn. By releasing such effecting means of detection, females do not waste energy flying about seeking mates and reserve all their energy for seeking out host plants appropriate for their larva. Saturniidae regardless of species are by no means ever abundant in the environment. The ability of the males to detect females of the same species from long distances allow them to maintain populations under low density. Female moths frequently will deposit eggs onto the same host plant that they developed on to reduce their weight to allow them to fly away. Large female luna sometimes are so heavy that they will deposit eggs on anything to reduce their weight enough to fly away.

Eggs:

large females are capable of laying up to three hundred eggs, but the average is two hundred. Host plant specificity allows the developing larva to more efficiently convert the consumed biomass into fat reserves and tissue. This influences the size of the adult and the possible number of ova that females can carry. Stunted females can carry up to as few as thirty – fifty eggs. Eggs are deposited on the undersides of host leaves in loose groups of three – eight. The eggs can hatch in as little as nine days, or as long as 14 days depending on temperature. They are round in shape and dark chocolate brown. Fertile eggs that are about to hatch take on a chalkier appearance and darken slightly. Luna are polyphagous, but depending on their range are highly specialized on a specific host species. Luna in northern ranges of Michigan are found exclusively on river birch (Betula nigra), and White birch (Betula papyrifera). Larval offspring from these populations will refuse acceptance of known food plants used by populations further south. This speaks to genetic aspects that allow certain populations to adapt on a particular host species developing that into a preferred host when nothing else occurs in that area. In general, luna prefer and do best on Black walnut (Juglens nigra). Some other host plants I have observed larva feeding on are: persimmon, and sweet gum.

Larva:

Larva of this species emerge light green with some first instar larva having black markings. They will consume all or part of the egg shell and soon after will begin to consume the leaves they find themselves upon. Larva of all saturniidae have 5 instars and luna disperse as soon as they hatch. Larva in their second instar are bright green with yellow tips on the back. The third instar larva are bright green with a wavy yellow mark running down each side and coarse black hairs on the back. The fourth and fifth instar are bright green with yellow green accents along the seams of each segment and along the spiracles. Some larva posses bright fuchsia spots scattered evenly over the larva. Once they have reached the fifth instar they continue to consume leaves at an incredible rate until they are ready to pupate. Larva turn an oranges brown when they ae ready to begin spinning their cocoon.

Cocoon:

Luna spin two types of cocoons, winter and summer. Winter cocoons are characterized by their color and texture. The silk fibers are dark brown and are of heavier substance. The larva incorporates leaves into the construction, but does not spin silk onto the petiole, thus allowing the leaf used to fall to the ground later in the season. Summer cocoons are spun with very light silk appearing cream to tan and spun with very flimsy thin silk walls. The cocoons also are constructed with holes which I surmise is to assist with venting excess heat and moisture. Inside the cocoon the larva spins course fibers that crisscross to suspend the pupa in the middle of the it. Cocoons produced in late summer and early fall have adapted to fall to the ground and be covered with litter. This provides camouflage and an insulated layer that protects the cocoons from extreme cold.

Pupa:

The pupa of this species is very smooth and is chestnut brown. A photosensitive patch located in the head region between the eyes is a clear window that allows the pupa to observe day length. This allows it to control emergence in areas of its range were temperature does not collaboratively work to signal enclosing. Pupa can be sexed with males have a wider more exaggerated antennae line than found on female pupal cases. Luna wiggle rapidly when disturbed and a bin full of cocoons sounds like a angry nest of wasps.

Eclose:

Luna emerge from early May to mid June during the late morning early afternoon. Luna do not spin an escape route like Promethia, and Cecropia, and rely on a enzyme called cocoonaise that breaks down the silken fibers. The moth has horny projections on the upper thorax it uses to cut and tear away at the soften silk and hydraulic pumping to push itself out of the cocoon. Once it breaks free from the cocoon it will crawl across the leaf litter until it finds something it can use to elevate itself to pump its wings and hang to dry. As nocturnal Saturniidae they wait till nightfall to take flight. Females reserve flight until they have been mated. It’s a general rule of thumb that if you capture a female at lights that she most likely has been mated and therefore eggs produced should be fertile.

Mortality factors:

Saturniidae larva are large and for most species defenseless. Birds readily seek out both the larva and adult moths. Moths drawn to night lights sit dazzled by the source where they are then picked off buildings once dawn emerges. Bats normally feed on small insects but will not pass up a large moth, leaving only wings as evidence. There are many parasitic fly and wasp species that utilize the larva as a host. Luna and all North American Lepidoptera have taken heavy tolls due to the release of the tachinid fly used in attempt to control gypsy moth populations. Larva can experience high mortality rates due to fungal, bacterial, and viral infection. The larva in nature have no real capacity to combat high density issues and have adapted to leave gregarious habits by the 3rd instar. Pupa are consumed in the winter by hungry squirrels, mice, and woodpeckers who can easily rip through the silk. Luna when disturbed during the day fall to the ground and flop about the ground exposing the eyes on both the upper and hind wings. This strategy is intended to frighten off birds/predators and allow the moth to escape. It has been my general observation however that birds quickly learn that they are quite edible and ignore the erratic behavior. I’m assuming that normally in the wild birds happen upon these so infrequently that it most likely is an effective means to avoid predation. Luna also have long hind wings that a predator would try to grasp and these frail tails tear off easily allowing the moth to escape similar to the effect certain lizards have that will drop their tail to escape.

Rearing notes:

Luna in my opinion are the easiest species of Giant North American silk moth to rear. Large numbers of larva can be bin reared and they rapidly develop. I have found that on average it takes a little over 30 days from egg to cocoon. This explains why this species often double broods in Michigan. Larva develop into summer non diapause pupa if the day length is greater that 11 hours during the third instar. Non diapause cocoons hatch in about 30 days from when they spin up.