Glasswing Butterfly
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''Greta oto'' is a species of
brush-footed butterfly The Nymphalidae are the largest family of butterflies, with more than 6,000 species distributed throughout most of the world. Belonging to the superfamily Papilionoidea, they are usually medium-sized to large butterflies. Most species have ...
and member of the subfamily
Danainae Danainae is a subfamily of the family Nymphalidae, the brush-footed butterflies. The group may be referred to as the Danaids (reflecting their previous rank as a family) or milkweed butterflies, as they often lay their eggs on various milkweed ...
, tribe
Ithomiini Ithomiini is a butterfly tribe in the nymphalid subfamily Danainae. It is sometimes referred to as the tribe of clearwing butterflies or glasswing butterflies. Some authors consider the group to be a subfamily (Ithomiinae). These butterflies ar ...
, and subtribe Godyridina. It is known by the common name glasswing butterfly for its transparent wings, which allow it to camouflage without extensive coloration. In Spanish-speaking regions, it may also be referred to as ''espejitos'', meaning "little mirrors" because of its transparent wings. The butterfly is mainly found in
Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
and northern regions of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
, with sightings as far north as
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
and as far south as
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
. While its wings appear delicate, the butterfly is able to carry up to 40 times its own weight.Lamas, G. (Ed.). (2004). ''Checklist: Part 4A. Hesperioidea - Papilionoidea''. ''In'': Heppner, J. B. (Ed.), ''Atlas of Neotropical Lepidoptera. Volume 5A''. Gainesville, Association for Tropical Lepidoptera; Scientific Publishers. In addition to its wing physiology, the butterfly is known for behaviors such as long
migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
s and
lekking A lek is an aggregation of male animals gathered to engage in competitive displays and courtship rituals, known as lekking, to entice visiting females which are surveying prospective partners with which to mate. It can also refer to a space us ...
. ''Greta oto'' closely resembles '' Greta andromica''.


Geographic range and habitat

The glasswing butterfly is most commonly found from Central to South America as far south as Chile, with appearances as north as
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
and Texas. This butterfly thrives in the
tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
conditions of the
rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...
s in the Central and South American countries.


Lifecycle


Egg

Eggs are typically laid on plants of the genus ''
Cestrum ''Cestrum'' is a genus of — depending on authority — 150-250 species of flowering plants in the family Solanaceae. They are native to warm temperate to tropical regions of the Americas, from the southernmost United States (Florida, Texas: day ...
'', a member of the nightshade family, which serves as a food source for their later life stages.


Larva

The
caterpillars 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 Sym ...
of the glasswing butterfly have green bodies, with yellow stripes in later stages. They are found on the host plants of the genus ''Cestrum''. The larvae are cylindrical in shape with
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 ...
projections that are smooth with filaments. These properties make the larvae extremely reflective, which essentially causes them to be invisible to predators.


Pupa

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 ...
are initially green with black specks, later becoming silver in colour. During the fifth
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 ...
stage, the pupa produces a
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...
pad on the lower surface of leaves through four spinning movements, onto which it attaches. The silk fibers are important in providing greater flexibility to the pupal attachment. The cremaster, a hooked bristle-like structure on the pupa, attaches to this silk pad by a series of lateral movements of the pupa's posterior abdomen. Pupal attachment failure occurs when the silk pad breaks. Additionally, the pupal attachment has high tensile strength and toughness, which prevent the pupa from being pulled by predators or breaking off in the wind, allowing it to swing safely.


Adult

The adult glasswing butterfly can be identified by its transparent wings with opaque, dark-brown borders tinted with red or orange. Its body is a dark brown color. The butterfly is long and has a
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 ...
of .


Food resources


Caterpillar

Poisonous plants of the genus ''
Cestrum ''Cestrum'' is a genus of — depending on authority — 150-250 species of flowering plants in the family Solanaceae. They are native to warm temperate to tropical regions of the Americas, from the southernmost United States (Florida, Texas: day ...
'' provide the best source of nutrition for the caterpillar; when larvae use other host plants, they often die in the first instar stage or develop more slowly. The caterpillars feed on these toxic plants and are perhaps toxic to predators through secondary chemicals stored in their tissues. For example, the caterpillar's chemical extracts are unpalatable to ''
Paraponera clavata ''Paraponera clavata'', commonly known as the bullet ant, is a species of ant known for its extremely painful Insect bites and stings, sting. It inhabits humid lowland rainforests in Central America, Central and South America. Etymology The Spe ...
'' ants.


Adult

The adult butterfly feeds mainly on the nectar of the flowers of the genus ''
Lantana ''Lantana'' () is a genus of about 150 species of perennial plant, perennial flowering plants in the verbena family, Verbenaceae. They are native to tropics, tropical regions of the Americas and Africa but exist as an introduced species in num ...
'', which includes 150 species of perennial flowering plants. They also eat flowers in the
Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...
and
Boraginaceae Boraginaceae, the Borago, borage or forget-me-not family, includes about 2,000 species of shrubs, trees, and herbs in 146 to 154 genus, genera with a worldwide distribution. The APG IV system from 2016 classifies the Boraginaceae as single famil ...
families and the droppings of insectivorous birds, absorbing
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...
that are later converted to proteins. Adult butterflies are also toxic due to the males consuming Asteraceae flowers whose nectar contains
pyrrolizidine alkaloids Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Their use dates back centuries and is intertwined with the discovery, understanding, and ...
.


Migration

The glasswing butterfly is migratory and travels up to per day at speeds of up to . It migrates to change
elevations The elevation of a geographic ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § ...
, which causes population density differences in varying geographical areas.


Predation

Birds are common predators of this butterfly. The glasswing combats predators by consuming
toxins A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
through plants of genus ''Cestrum'' and family Asteraceae in both the caterpillar and butterfly stages. Toxin consumption gives the butterfly a foul taste that discourages predation.


Protective coloration

This butterfly uses its transparency to hide from predators by
camouflaging Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
into the background during flight. Transparency is a rare trait among the
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 ...
; they more commonly use
mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. In the simples ...
to ward off predators.


Mating

This butterfly species mates polygynously, with males attempting to obtain one or more female mates per breeding season.


Lekking

To attract females, male butterflies form
leks Lek or LEK may refer to: * Lek mating, of animals * Albanian lek, currency * Lek (magazine), Norway * Lek (pharmaceutical company), now part of Sandoz * Lek (river), Netherlands * De Lek, Netherlands fiefdom * L.E.K. Consulting, firm * Leung ...
, or large gatherings, where males compete for mates. They gather in shaded areas of the
rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...
and competitively display themselves to attract mates. Male glasswing butterflies also release
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 during lekking to attract females. The pheromones produced are derived from
pyrrolizidine alkaloid Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Their use dates back centuries and is intertwined with the discovery, understanding, and e ...
s that the butterflies obtain through their diet of plants of the Asteraceae. The alkaloids are then converted to pheromones through the formation of a pyrrole ring, followed by ester cleavage and oxidation. Additionally, since the process by which the pheromone is produced is not only formed by butterflies and moths themselves, but also derived from plants, as with the glasswing butterfly, the pheromone is unlikely to be used to distinguish between species.


Physiology


Wings

Wing transparency in ''Greta oto'' results from the combination of several properties; low absorption of
visible light Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...
, low scattering of the light that passes through the wings, and low reflection of the light impinging on the wing's surface occurs. The last occurs for a broad range of incident
wavelengths In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same '' phase'' on ...
, covering the entire
visible spectrum The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optica ...
, and all incidence angles. This broadband and omnidirectional antireflection property originates from nanopillars standing on the wing's surface, which ensures a gradient of
refractive indices In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
between the incident medium, air, and the wing's membrane. These nanopillars, seemingly randomly arranged on the wing's surface, possess a high aspect ratio (defined as height divided by radius), where the radii are below the wavelengths of the visible light. Additionally, they feature a random height and width distribution, which is directly responsible for the smooth refractive index gradient, thereby giving the broadband and omnidirectional antireflection properties. These properties are further improved by the presence of pedestals at the base of the nanopillars. Additionally, the structure of the nanopillars allows for the wings to have a low roughness factor because of its tiny hair-like
microtrichia Insect morphology is the study and description of the morphology (biology), physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical f ...
features. This was experimentally tested through water droplet adhesion to the wings. Basically, it reflects light and is transparent because of nanopillars that make up the wing.


Conservation

These parks and reserves in
Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...
currently feature the glasswing butterfly and are working on their conservation:
Guanacaste National Park Guanacaste National Park may refer to: * Guanacaste National Park (Belize) *Guanacaste National Park (Costa Rica) Guanacaste National Park, in Spanish is a national park in northern Costa Rica. The park is part of the Area de Conservación Gua ...
, Rincón de la Vieja National Park,
Monteverde Cloud Forest Reserve The Monteverde Cloud Forest Reserve () is a Costa Rican reserve located along the Cordillera de Tilarán within the Puntarenas and Alajuela provinces. Named after the nearby town of Monteverde and founded in 1972, the Reserve consists of ove ...
,
Palo Verde National Park Palo Verde National Park (), is a national park of Costa Rica, part of the Arenal Tempisque Conservation Area, that contains much of the area of the valley of the Tempisque River and covers an area of in Guanacaste Province, 30 km west of ...
,
Carara National Park Carara National Park is a national park in the Central Pacific Conservation Area located near the Pacific coast of Costa Rica. It was established on 27 April 1978 as a biological reserve, but its growing popularity after 1990 forced the governmen ...
, Poás Volcano National Park, La Selva Reserve and Biological Station, Juan Castro Blanco National Park, Irazú Volcano National Park,
Chirripó National Park Chirripó National Park is a national park of Costa Rica, encompassing parts of three provinces: San José, Limón and Cartago. It was established in 1975. It is part of the Talamanca Range-La Amistad Reserves/La Amistad National Park UNESCO W ...
, and
La Amistad International Park La Amistad International Park, or in Spanish , formerly La Amistad National Park, is a transboundary protected area in Latin America, management of which is shared between Costa Rica ( Caribbean La Amistad and Pacific La Amistad Conservation Area ...
.


References

{{Taxonbar, from=Q2662974 Ithomiini Butterflies of Central America Nymphalidae of South America Lepidoptera of Colombia Lepidoptera of the United States Butterflies described in 1854 Lepidoptera of Mexico Lepidoptera of Chile