Luna moth: Actias luna (Linnaeus, 1758)

Female Actias luna moth on sweetgum courtesy of John H. Campbell.

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TAXONOMY: Superfamily: Bombycoidea Latreille, 1802 Family: Saturniidae Boisduval, [1837] 1834 Subfamily: Saturniinae Boisduval, [1837] 1834 Tribe: Saturniini Boisduval, [1837] 1834 Genus: Actias Leach, 1815

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DISTRIBUTON:

The luna moth, Actias luna (wingspan 4.5-5.0 inches), is very common in many counties of the eastern states from Maine to Florida and generally becomes less plentiful as one moves westward to Texas and the Great Plains. Lunas are found in many Canadian provinces: Nova Scotia, P.E.I., New Brunswick, and in southern portions of Quebec, Ontario, Manitoba, and Saskatchewan.

FLIGHT TIMES AND PREFERRED FOOD PLANTS:

In Canada and the northern border states within its range, the luna caterpillar shows a preference for white/paper birch (Betula paperifera), and the moth is usually single brooded with most adults flying from late May to early July.

In New Jersey and states of that general latitude, caterpillars consume hickory, walnut, and sweetgum. Double brooded stock first appears from late April to May with the second brood appearing nine to eleven weeks later.

In the more southern latitudes, larvae favour persimmon. Adult moths fly at eight to ten week intervals starting in March, allowing for at least three broods. Adult Actias luna have been taken in every month in Louisiana.

Lunas which emerge in the spring often have a red lateral line on each side of the body and usually have narrow outer red margins on both fore and hind wings. This red colouration is absent from subsequent broods.

ECLOSION:

Adults usually eclose from their cocoons in mid morning. The cocoon is rather flimsy and valveless. The moth makes quite a racket as it heaves itself against one end of the cocoon, tearing at the silk with hornlike projections near the base of the forewing. A secretion called cocoonase helps to break down the sericin binding the silk.

Photo courtesy John H. Campbell

The soft moth (female to left, note narrow antennae) can escape through a hole roughly 3/8 inch in diameter. Once out of the cocoon, the moth must climb to hang its wings for inflation. I place my luna cocoons in a 11" x11" x 2' emerging cage made out of folded hardware cloth with a 1/2 inch mesh. The newly emerged, soft, pliant moths climb up the wire and hang from either the top or upper reaches of the sides. Photo courtesy of John H. Campbell

Despite having witnessed hundreds of eclosions in my lifetime, I still often pause to watch lunas eclose and inflate in emergence cages. All of the giant Saturniidae pump fluid into veins in soft stubbly wings while hanging from stems, tree trunks, etc. Photo courtesy of John H. Campbell. The adult Saturniidae moths have no mouth parts or feeding tubes. The moths live for 7-10 days as adults, utilizing fats stored from caterpillar days.

The entire process seldom takes more than half an hour, and in another few hours the fully inflated wings have stiffened in preparation for flight.

Even the giant atlas ecloses with wing stubs seldom more than one inch long.

SCENTING AND MATING:

At approximately 10:30 pm (as early as 9:00 pm in early spring) the female moth extends a scent gland from the posterior of her abdomen and begins releasing an air borne pheromone. This scent attracts the male.

Once coupled, the pair will remain that way until the following evening. In captivity siblings will mate readily, even in a small cage. Wild males are easily attracted. Scenting or "calling" usually continues until around 1:00 am or until the female has mated, whichever comes first.

Males usually emerge a day or two before females and it is rare that an unmated female would be captured at a light as females usually don't fly until after mating.

EGGS, CATERPILLARS, COCOONS, AND PUPAE:

Gravid female moths lay 4-6 gray-brown cylindrical eggs with concave tops on the underside of food plant leaves. Females have a capacity of 150-250 eggs. Incubation time is 8-13 days depending on temperature and humidity. Females readily deposit eggs in inflated brown paper sandwich or grocery bags for those who wish to rear this species.

Caterpillars, which grow to approximately 3.5 inches (9 cm.), are predominantly green throughout their five instars and spend roughly one week in each stage except the longer fifth instar. Larvae which are going to overwinter in the pupae/cocoon stage take on a dark amber or burgundy-brown colouration just prior to spinning cocoons.

Some caterpillars will use a leaf wrap while others descend to spin up among whatever ground protection they can find. Mature larvae "clear their guts" with a loose, runny stool just prior to cocooning.

Luna cocoons are papery thin and pupae outlines can easily be seen when the cocoon is held up to a bright light. Winter diapause stock tends to spin a courser, darker silk. In regions of the United States where lunas are double or triple brooded 25-40% of early brood stock caterpillars will spin the darker cocoon and overwinter instead of eclosing that same summer.

I store my winter diapause stock in small (sandwich sized), tightly-lidded containers (no air holes) holding 10-20 cocoons each in the refrigerator crisper. I have not had problems with dessication even though I do not mist the cocoons. Cocoons may also be stored outdoors in a more natural environment in protective cages.

The pupae are dark brown and the antennae outline can be seen on the pupal shell to determine sexes.

Click on food plant information to see a caterpillar image and a listing of foodplants.

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