Luna Moth
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The luna moth (''Actias luna''), also called the American moon moth, is a
Nearctic The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...
moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
in the family
Saturniidae Saturniidae, members of which are commonly named the saturniids, is a family of Lepidoptera with an estimated 2,300 described species. The family contains some of the largest species of moths in the world. Notable members include the emperor m ...
, subfamily Saturniinae, a group commonly named the giant silk moths. The moth has lime-green wings and a white body. Its
caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...
s are also green. Its typical
wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the opposite wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingsp ...
is roughly , but wingspans can exceed , ranking the species as one of the larger moths in
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
. Across Canada, it has one generation per year, with the winged adults appearing in late May or early June, whereas farther south it will have two or even three generations per year, the first appearance as early as March in southern parts of the United States. As
defense mechanism In psychoanalytic theory, defence mechanisms are unconscious psychological processes that protect the self from anxiety-producing thoughts and feelings related to internal conflicts and external stressors. According to this theory, healthy ...
s, larvae emit clicks as a warning and can also regurgitate intestinal contents, confirmed as having a deterrent effect on a variety of predators. The elongated tails of the hindwings are thought to confuse the echolocation detection used by predatory bats. A parasitoid fly deliberately introduced to North America as a
biological pest control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or ot ...
for the
invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
spongy moth ''Lymantria dispar'', also known as the gypsy moth or the spongy moth, is a species of moth in the family Erebidae native to Europe and Asia. ''Lymantria dispar'' is subdivided into several subspecies, with subspecies such as '' L. d. dispar'' ...
(also known as gypsy moth) appears to have had a negative impact on luna moths and other native moths.


Description

Eggs, attached in small groups to undersides of leaves, are mottled white and brown, slightly oval, and roughly 1.5 millimeters in diameter. Larvae are primarily green, with sparse hairs. The first
instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
, emerging from the egg, reaches a length of , the second , the third and the fourth . The fifth (final) instar grows to approximately in length. Small, colorful dots – yellow or magenta – may line the sides of the fourth and fifth instars. The larvae may take on a reddish-brown color just prior to cocooning. Fifth-instar larvae descend to the ground and use silk to bind dead leaves around the cocoon. The
imago In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the ''imaginal'' stage ("imaginal" being "imago" in adjective form), the stage in wh ...
es (winged, sexually mature), often referred to as adult moths, emerge from the
pupae A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...
with the wings small, crumpled and held close to the body. Over several hours the wings will enlarge to full size. Wingspan is typically , and in rare instances as much as . Females and males are similar in size and appearance: green wings, eyespots on both forewings and hind wings, and long, sometimes somewhat twisted tails extending from the back edge of the hindwings. Bodies are white and hairy. Adults have
vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
mouthparts and do not feed. Energy is from fat stores created while a caterpillar. The forward edge of the forewing is dark-colored and thick, tapering in thickness from the thorax to the wing tip. Its color can range from maroon to brown. The eyespots, one per wing, are oval in shape on the forewings and round on the hindwings. Each eyespot can have arcs of black, blue, red, yellow, green or white. The eyespots are thought to confuse potential predators. There are some sex-determined and regional differences in appearance. Females will have a larger abdomen compared to males because it contains 200–400 eggs. Both sexes have antennae, but on the male, much longer and wider. Wing color is blue-green in the north and for the overwintering generation in the central and southern states; second and third generation wing color has more of a yellow-green tint.


Etymology

Described and named ''Phalena plumata caudata'' by
James Petiver James Petiver () was a London apothecary, a fellow of the Royal Society as well as London's informal Temple Coffee House Botany Club, famous for his specimen collections in which he traded and study of botany and entomology. He corresponded with ...
in 1700, this was the first North American saturniid to be reported in the insect literature.. The initial Latin name, which roughly translates to "brilliant, feather tail", was replaced when
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
described the species in 1758 in the tenth edition of
Systema Naturae ' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...
, and renamed it ''Phalaena luna'', later ''Actias luna'', with ''luna'' derived from
Luna Luna commonly refers to: * Earth's Moon, named "Luna" in Latin, Spanish and other languages * Luna (goddess) In Sabine and ancient Roman religion and myth, Luna is the divine embodiment of the Moon (Latin ''Lūna'' ). She is often presented as t ...
, the Roman moon goddess. The common name became "Luna moth". Several other North American giant silk moths were also given species names after Roman or Greek mythology.


Distribution

The Luna moth is found in North America, from east of the
Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...
in the United States –
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
to
Maine Maine ( ) is a U.S. state, state in the New England region of the United States, and the northeasternmost state in the Contiguous United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Provinces and ...
, and from
Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...
eastward through central
Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...
to
Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...
in
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
. Luna moths are also rarely found in Western Europe as
vagrants Vagrancy is the condition of wandering homelessness without regular employment or income. Vagrants usually live in poverty and support themselves by travelling while engaging in begging, scavenging, or petty theft. In Western countries, ...
.


Life cycle

Based on the
climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...
in which they live, Luna moths produce different numbers of
generation A generation is all of the people born and living at about the same time, regarded collectively. It also is "the average period, generally considered to be about 20–⁠30 years, during which children are born and grow up, become adults, and b ...
s per year. In Canada and northern regions of the United States, they are
univoltine Voltinism is a term used in biology to indicate the number of broods or generations of an organism in a year. The term is most often applied to insects, and is particularly in use in sericulture, where silkworm varieties vary in their voltinism. ...
, meaning one generation per year. Life stages are approximately 10 days as eggs, 6–7 weeks as larvae, 2–3 weeks as pupae, finishing with one week as winged adults appearing in late May or early June. In the mid-Atlantic states, the species is bivoltine, characterized by two generations per year. In contrast, farther south, they are trivoltine, producing three generations within the same time frame. In the central states, the first generation appears in April, the second in July. Even farther south, the first generation appears as early as March, with the second and third spaced eight to ten weeks later.


Eggs

Females lay 200–400 eggs, singly or in small groups, on the underside of leaves of the tree species preferred by the larvae. Egg laying starts the evening after mating is completed and goes on for several days. Eggs hatch in about a week.


Larvae

Each
instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
– the period between molts – generally takes about 4–10 days. There are five instars before cocooning. At the end of each instar, a small amount of silk is placed on the major vein of a leaf and the larva undergoes
apolysis Apolysis ( "discharge, lit. absolution") is the separation of the cuticle from the epidermis in arthropods and related groups (Ecdysozoa). Since the cuticle of these animals is also the skeletal support of the body and is inelastic, it is shed dur ...
, then
ecdysis Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remnant ...
(molting), leaving the old
exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...
behind. Sometimes the shed exoskeleton is eaten. Newly hatched, this caterpillar constantly munches on the leaves of walnut, hickory, sweetgum, and paper birch trees. Each instar is green, though the first two instars do have some variation in which some larvae will have black underlying splotches on their
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...
side. The final instar grows to approximately in length. All five instar stages possess green spines on the dorsal surface. These spines do not sting, but can still cause irritation upon contact. This is a tree-dwelling species. Larvae stay on the same tree where they hatched until it is time to descend to the ground to make a cocoon. When females emerge from cocoons, they fly to preferred tree species, emit pheromones, and wait there for males to find them. Although some larvae in the family
Saturniidae Saturniidae, members of which are commonly named the saturniids, is a family of Lepidoptera with an estimated 2,300 described species. The family contains some of the largest species of moths in the world. Notable members include the emperor m ...
are known to be poisonous, those of ''A. luna'' are not. The spines, or setae, located on the thoracic and abdominal segments have no chemical component to them.


Pupae

The Luna moth
pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...
tes after spinning a silk cocoon, which is thin and single layered. Shortly before pupation, the final, fifth-instar caterpillar will engage in a "gut dump" where any excess water and intestinal contents are expelled. As pupae, this species is more physically active than most moths. When disturbed, the moths will wiggle within their pupal cases, producing a noise. Pupation takes approximately two weeks unless the individual is in
diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...
over winter, in which case the pupal stage takes about nine months. The mechanisms triggering diapause are generally a mixture of genetic triggers, duration of sunlight and temperature. The pupae have chitinous spurs near the base of the forewings. By vigorously moving about within the cocoon, these spurs tear a circular opening from which the imago emerges, the silk of the cocoon having also been weakened by the secretion of cocoonase, a protein-digesting enzyme.


Imago (winged)

Pupae transition to winged state after receiving external signals in the form of temperature change. When the adult Luna moths emerge from their pupae, their abdomens are swollen and their wings are small, soft and wet. The first few hours of adult life will be spent pumping
hemolymph Hemolymph, or haemolymph, is a fluid, similar to the blood in invertebrates, that circulates in the inside of the arthropod's body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph c ...
(invertebrates' equivalent to blood) from the abdomen into the wings. The moths must wait for the wings to dry and harden before being able to fly. This process can take 2–3 hours to complete. Luna moths are not rare, but are rarely seen due to their very brief (7–10 day) adult lives and
nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...
flying time. As with all giant silk moths, the adults only have vestigial mouthparts and no digestive system and therefore do not eat in their adult form. Instead, they rely on energy stored during their caterpillar stage. In regions where there are two or three generations per year, the second and third may have wing coloration that is more of a yellow-green compared to the first generation of the year.


Mating

Giant silk moths have in common a mating process wherein the females, at night, release volatile sex
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s, which the males, flying, detect via their large antennae. Males can detect these molecules at a distance of several miles, and then fly in the direction the wind is coming from until reaching the female. Luna moth females mate with the first males to find them, a process that typically starts after midnight and takes several hours. Researchers extracted three chemical compounds from the pheromone gland of unmated Luna moth females and identified one major and two minor aldehyde compounds designated ''E''6,''Z''11-18:Ald, ''E''6-18:Ald and ''Z''11-18:Ald. The same compounds were also synthesized. Field experiments with both unmated females and the synthesized compounds confirmed that E6, Z11-18:Ald was the major sex pheromone, attraction augmented by the addition of E6-18:Ald but not by Z11-18:Ald. The authors mentioned that no other moth species were attracted to either the unmated females or the synthesized products, confirming that the pheromone is species-specific, at least for the sites and dates where it was tested.


Gallery of life cycle

File:Actias luna eggs sjh.JPG, Eggs from female raised in captivity, laid on coarse paper File:Actias luna 1st instar hatching sjh.jpg, Hatching larva File:Actias luna 4th instar sjh.JPG, 4th-instar larva. Spots can also be yellow or magenta. File:Actias luna spinning sjh.JPG, 5th-instar larva starting to create a cocoon (note silk strands to leaves) File:Actias luna male pupa sjh.JPG, Pupa, removed from cocoon. Eyes visible at head end (left) File:Actias luna emergence male 7 sjh.JPG, Wings drying and enlarging after emergence from pupa File:Actias luna mating sjh.JPG, Mating imagoes (winged adults). Male, with larger antennae, on left


Close-up images

File:Luna Moth, closeup of antennae.jpg, Antennae (male) File:Actias luna eyespot sjh.JPG, Eye-spot on hindwing File:Luna moth eye spot.jpg, Eye-spot on forewing File:Luna moth scales.jpg, Extreme close-up of scales in eye-spot


Predators and parasites

Some species of giant silk moth larvae are known to make clicking noises when attacked by rubbing their serrated mandibles together and can release a regurgitation of distasteful fluids. These clicks are audible to humans and extend into ultrasound frequencies audible to predators. Clicks are thought to be a form of
aposematic Aposematism is the Advertising in biology, advertising by an animal, whether terrestrial or marine, to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the pr ...
warning signaling, made prior to predator-deterring regurgitation of intestinal contents. Luna moth larvae click and regurgitate, with the regurgitated material confirmed as being a predator deterrent against several species.
Imago In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the ''imaginal'' stage ("imaginal" being "imago" in adjective form), the stage in wh ...
s (winged adults) of this and related night-flying '' Actias'' species, collectively referred to as "moon moths", have long hindwing tails. A "false target" hypothesis holds that the tails evolved to reduce predation risk by bats which use echolocation to locate prey. The moths use the spinning hindwing tails to fool bats into attacking nonessential appendages, with success occurring over 55% of the time. Experiments were conducted with Luna moths with intact wings and with the tails removed. With intact wings, a majority of the attacking bats contacted the hindwing tails rather than the body of the moth; only 35% of intact moths were caught versus 81% for those with clipped tails. The results of this experiment support echolocation distortion as an effective countermeasure. The parasitoid tachinid fly '' Compsilura concinnata'' native to Europe was deliberately introduced to the United States throughout much of the 20th century as a biological control for the gypsy moth (''Lymantria dispar'') (also known as the "spongy moth").Multiple sources: * * Researchers reported that when Luna moth larvae were placed outside for about a week and then collected and returned to the laboratory, four parasitic species emerged, the most common being ''C. concinnata''. The researchers concluded that this parasitoid fly causes collateral damage to Luna moth populations.Multiple sources: * * Luna moth larvae have displayed defenses against predators in late instars by developing spines once they reach about 3 cm in length. Unlike other species such as '' Automeris io'', which have chemical defenses much earlier in the larval stage, the Luna moth larvae are left largely defenseless until it reaches this length. However, the absence of a chemical defense allows for the shortening of the larval stage. ''Automeris io'' has a larval stage at least twice as long on average as ''Actias luna'', leaving it vulnerable to
parasitism Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...
.


Host plants

The larvae of Luna moths feed on several different species of broadleaf trees. The larvae do not reach population densities sufficient to cause significant damage to their host trees. Tuskes listed white birch (''
Betula papyrifera A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contain ...
''), American persimmon ('' Diospyros virginiana''), American sweet gum (''
Liquidambar styraciflua ''Liquidambar styraciflua'', commonly known as the American sweetgum among other names, is a deciduous tree in the genus ''Liquidambar'' native to warm temperate areas of eastern North America and tropical montane regions of Mexico and Central A ...
''), plus several species of
hickory Hickory is a common name for trees composing the genus ''Carya'', which includes 19 species accepted by ''Plants of the World Online''. Seven species are native to southeast Asia in China, Indochina, and northeastern India (Assam), and twelve ...
(''Carya''),
walnut A walnut is the edible seed of any tree of the genus '' Juglans'' (family Juglandaceae), particularly the Persian or English walnut, '' Juglans regia''. They are accessory fruit because the outer covering of the fruit is technically an i ...
(''Juglans'') and
sumac Sumac or sumach ( , )—not to be confused with poison sumac—is any of the roughly 35 species of flowering plants in the genus ''Rhus'' (and related genera) of the cashew and mango tree family, Anacardiaceae. However, it is '' Rhus coriaria ...
(''Rhus'') as host plants for the caterpillars. Other tree species have been identified as suitable for ''Actias luna'' larvae, but a feeding experiment that also included
black cherry ''Prunus serotina'', commonly called black cherry,World Economic Plants: A Standard Reference, Second Edition'. CRC Press; 19 April 2016. . p. 833–. wild black cherry, rum cherry, or mountain black cherry, is a deciduous tree or shrub in the r ...
, eastern cottonwood,
quaking aspen ''Populus tremuloides'' is a deciduous tree native to cooler areas of North America, one of several species referred to by the common name aspen. It is commonly called quaking aspen,
, white willow,
red oak ''Quercus'' subgenus ''Quercus'' is one of the two subgenera into which the genus ''Quercus'' was divided in a 2017 classification (the other being subgenus ''Cerris''). It contains about 190 species divided among five sections. It may be calle ...
,
white oak ''Quercus'' subgenus ''Quercus'' is one of the two subgenera into which the genus ''Quercus'' was divided in a 2017 classification (the other being subgenus ''Cerris''). It contains about 190 species divided among five sections. It may be calle ...
and tulip tree reported very poor survival on these seven tree species even though older literature had identified them as hosts. The author suggested that host plant utilization may differ regionally, so that larvae collected from one region may not tolerate host plants readily consumed in another region (northern populations often lose the ability to digest sweetgum, while southern ones may undergo the same with willows). Biochemical detoxification of host plant defensive chemicals by digestive system enzymes may be a factor in regional host plant specialization.
Juglone Juglone, also called 5-hydroxy-1,4-naphthalenedione (IUPAC) is a phenolic organic compound with the molecular formula C10H6O3. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500. It is insoluble in benzene but s ...
is a chemical compound common to walnut and hickory which most insects find a deterrent or even toxic. Luna moth larvae have higher concentrations of juglone-neutralizing digestive system enzymes compared to other
lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...
, and concentrations were even higher when larvae were fed walnut or hickory leaves versus white birch or American sweet gum. This suggests evolutionary and inducible adaptations to allow consumption of certain host plants.


In popular culture

The Luna moth appeared on a first class United States postage stamp issued in June 1987. Although more than two dozen butterflies have been so honored, as of 2019 this is the only moth.


References


External links


Luna moth info



''Actias luna'' at www.butterfliesandmoths.org

''Actias luna'' at Moths of North Carolina
{{Authority control luna moth Moths described in 1758 Moths of North America Taxa named by Carl Linnaeus