Welcome to the I Can't Sleep Podcast,
Where I help you drift off one fact at a time.
I'm your host Benjamin Boster and tonight's episode is about butterflies.
Butterflies are winged insects from the Lepidopteran superfamily Papillionoidea,
Characterized by large,
Often brightly colored wings that often fold together when at rest and at conspicuous fluttering flights.
The oldest butterfly fossils have been dated to the Paleocene,
About 56 million years ago.
Though molecular evidence suggests that they likely originated in the Cretaceous.
As holometabolous insects,
Butterflies undergo complete metamorphosis,
Meaning that their life cycle comprises four stages.
Winged adults lay eggs on plant foliage,
On which their larvae,
Known as caterpillars,
Will feed.
The caterpillars grow,
Sometimes very rapidly,
And when fully developed,
Pupate in chrysalis.
When metamorphosis is complete,
The pupil's skin splits,
The adult insect climbs out,
Expands its wings to dry,
And flies off.
Some butterflies,
Especially in the tropics,
Have several generations in a year,
While others have a single generation.
And a few in cold locations may take several years to pass through their entire life cycle.
Butterflies are often polymorphic,
And many species make use of camouflage,
Mimicry,
And anaposematism to evade their predators.
Feism is when a butterfly doesn't fully undergo melanism.
Some,
Like the monarch and the painted lady,
Migrate over long distances.
Some species are pests because in their larval stages they can damage domestic crops or trees.
Other species are agents of pollination of some plants.
Larvae of a few butterflies,
E.
G.
Harvesters,
Eat harmful insects,
And a few are predators of ants,
While others live as mutualists in association with ants.
Culturally,
Butterflies are a popular motif in the visual and literary arts.
The Smithsonian Institution says butterflies are certainly among the most appealing creatures in nature.
The Oxford English Dictionary derives the word straightforwardly from Old English,
Butterfly.
Similar names in Old Dutch and Old High German show that the name is ancient,
But modern Dutch and German use different words,
Vlinder and schmetterling.
And the common name often varies substantially between otherwise closely related languages.
A possible source of the name is the bright yellow mail of the brimstone.
Another is that butterflies were on the wing in meadows during the spring and summer butter season while the grass was growing.
Butterfly adults are characterized by their four scale-covered wings,
Which give the Lepidoptera their name,
Ancient Greek lepis,
Scale,
Plus teron,
Wing.
These scales give butterfly wings their color.
They are pigmented with melanins that give them blacks and browns,
As well as uric acid derivatives and flavons that give them yellows.
But many of the blues,
Greens,
Reds,
And iridescent colors are created by structural coloration produced by the microstructures of the scales and hairs.
As in all insects,
The body is divided into three sections,
The head,
Thorax and abdomen.
The thorax is composed of three segments,
Each with a pair of legs.
In most families of butterfly,
The antennae are clubbed,
Unlike those of moths,
Which may be thread-like or feathery.
The long plebiscis can be coiled when not in use for sipping nectar from flowers.
Nearly all butterflies are diurnal,
Have relatively bright colors,
And hold their wings vertically above their bodies when at rest.
These features differentiate butterflies from the majority of moths,
Which fly by night,
Or often cryptically colored,
Well camouflaged,
And either hold their wings flat touching the surface on which the moth is standing,
Or fold them closely over their bodies.
Some day-flying moths,
Such as the hummingbird hawkmoth,
Are exceptions to these rules.
Butterfly larvae,
Caterpillars,
Have a hard head with strong mandibles used for cutting their food,
Most often leaves.
They have cylindrical bodies with 10 segments to the abdomen,
Generally with short prolegs on segments 3 through 6 and 10.
The three pairs of true legs on the thorax have five segments each.
Many are well camouflaged.
Others are aposematic,
With bright colors and bristly projections containing toxic chemicals obtained from their food plants.
The pupa or chrysalis,
Unlike that of moths,
Is not wrapped in a cocoon.
Butterflies are distributed worldwide,
Except Antarctica,
Totaling some 18,
500 species.
The monarch butterfly is native to the Americas,
But in the 19th century or before spread across the world,
And is now found in Australia,
New Zealand,
Other parts of Oceania,
And the Iberian Peninsula.
It is not clear how it dispersed.
Adults may have been blown by the wind,
Or larvae or pupae may have been accidentally transported by humans.
But the presence of suitable host plants in their new environment was a necessity for their successful establishment.
Many butterflies,
Such as the Painted Lady,
Monarch,
And several Danaan,
Migrate for long distances.
These migrations take place over a number of generations,
And no single individual completes the whole trip.
The eastern North American population of monarchs can travel thousands of miles southwest to overwintering sites in Mexico.
There is a reverse migration in the spring.
It has recently been shown that the British Painted Lady undertakes a 9,
000 mile round trip,
And a series of steps by up to six successive generations.
From tropical Africa to the Arctic Circle.
Almost double the length of the famous migrations undertaken by monarchs.
Spectacular large-scale migrations associated with the monsoon are seen in peninsular India.
Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.
Butterflies navigate using a time-compensated sun compass.
They can see polarized light and therefore orient even in cloudy conditions.
The polarized light near the ultraviolet spectrum appears to be particularly important.
Many migratory butterflies live in semi-arid areas,
Where breeding seasons are short.
The life histories of their host plants also influence butterfly behavior.
Butterflies in their adult stage can live from a week to nearly a year,
Depending on the species.
Many species have long larval life stages,
While others can remain dormant in their pupal or egg stages and thereby survive winters.
The Melissa Arctic overwinders twice as a caterpillar.
The number of generations per year varies from temperate to tropical regions,
With tropical regions showing a trend towards multi-volcanism.
Butterfly eggs are protected by a hard,
Rigid outer layer of shell called the corian.
This is lined with a thin coating of wax which prevents the egg from drying out before the larva has had time to fully develop.
Each egg contains a number of tiny funnel-shaped openings at one end,
Called micropoles.
Butterfly eggs vary greatly in size and shape between species,
But are usually upright and finely sculpted.
Some species lay eggs singly,
Others in batches.
Many females produce between 100 and 200 eggs.
Eggs are almost invariably laid on plants.
Each species of butterfly has its own host plant range.
And while some species of butterfly are restricted to just one species of plant.
Others use a range of plant species,
Often including members of a common family.
In some species,
Such as the Great Spangled Fritillary,
The eggs are deposited close to but not on the food plant.
This most likely happens when the egg overwinters before hatching,
And where the host plant loses its leaves in winter,
As do violets in this example.
The egg stage lasts a few weeks in most butterflies,
But eggs laid close to winter,
Especially in temperate regions,
Go through a diapause,
Resting stage,
And the hatching may take place only in spring.
Some temperate region butterflies,
Such as the Camberwell Beauty,
Lay their eggs in the spring and have them hatch in the summer.
Butterfly larvae or caterpillars,
Consume plant leaves,
And spend practically all of their time searching for and eating food.
Although most caterpillars are herbivorous,
A few species are predators.
Spelgis aepeus eats scale insects,
While lycanids such as Lyphora brassilis or Myrmecophilus eating ant larvae.
Some larvae form mutual associations with ants.
They communicate with ants using vibrations that are transmitted through the substrate as well as using chemical signals.
The ants provide some degree of protection to these larvae,
And they in turn gather honeydew secretions.
Caterpillars mature through a series of developmental stages known as instars.
At the end of each instar,
The larvae molds.
The old cuticle splits and the new cuticle expands,
Rapidly hardening and developing pigment.
When the larva is fully grown,
Hormones are produced.
At this point the larva stops feeding and begins wandering in the quest for a suitable pupation site,
Often the underside of a leaf or other concealed location.
There it spins a button of silk which it uses to fasten its body to the surface and molts for a final time.
While some caterpillars spin a cocoon to protect the pupa,
Most species do not.
The naked pupa,
Often known as chrysalis,
Usually hangs head down from the cremaster,
A spiny pad at the posterior end.
But in some species,
A silken girdle may be spun to keep the pupa in a head up position.
Most of the tissues and cells of the larvae are broken down inside the pupa,
As the constituent material is rebuilt into the imago.
The structure of the transforming insect is visible from the exterior,
With the wings folded flat on the ventral surface,
And the two halves of the proboscis,
With the antennae and the legs between them.
The pupil transformation into a butterfly through metamorphosis has held great appeal to mankind.
To transform from the miniature wings visible on the outside of the pupa into large structures usable for flight,
The pupal wings undergo rapid mitosis and absorb a great deal of nutrients.
If one wing is surgically removed early on,
The other three will grow to a larger size.
Several boundaries seen in the adult color pattern are marked by changes in the expression of particular transcription factors in the early pupa.
Many Heliconius butterflies also use their proboscis to feed on pollen.
In these species,
Only 20% of the amino acids used in reproduction come from larval feeding,
Which allow them to develop more quickly as caterpillars,
And gives them a longer lifespan of several months as adults.
The thorax of the butterfly is devoted to locomotion.
Each of the three thoracic segments has two legs.
Among nympholids,
The first pair is reduced and the insects walk on forelegs.
The second and third segments of the thorax bear the wings.
The leading edges of the fore wings have thick veins to strengthen them,
And the hind wings are smaller and more rounded and have fewer stiffening veins.
The fore wings and the hind wings are not hooked together,
As they are in moths,
But are coordinated by the friction of their overlapping parts.
The front two segments have a pair of spiracles which are used in respiration.
Butterflies feed primarily on nectar from flowers.
Some also derive nourishment from pollen,
Tree sap,
Rotting fruit,
And dissolved minerals in wet sand or dirt.
Butterflies are important as pollinators for some species of plants.
In general,
They do not carry as much pollen load as bees,
But they are capable of moving pollen over great distances.
Flower constancy has been observed for at least one species of butterfly.
Adult butterflies consume only liquids ingested through their pupae.
They sip water from damp patches for hydration,
And feed on nectar from flowers,
From which they obtain sugars for energy,
And sodium and other minerals vital for reproduction.
Several species of butterflies need more sodium than that provided by nectar,
And are attracted by sodium and salt.
They sometimes land on people,
Attracted by the salt and human sweat.
In hilltopping,
Males of some species seek hilltops and ridgetops,
Which they patrol and search for females.
Since it usually occurs in species with low population density,
It is assumed these landscape points are used as meeting places to find mates.
Butterflies use their antennae to sense the air for wind and scents.
The antennae come in various shapes and colors.
The Hesperides have a pointed angle or hook to the antennae.
While most other families show nobdentony.
The antennae are richly covered with sensory organs known as sensoli.
A butterfly's sense of taste is coordinated by chemoreceptors on the tarsi,
Or feet,
Which work only on contact,
And are used to determine whether an egg-laying insect's offspring will be able to feed on a leaf before eggs are laid on it.
Many butterflies use chemical signals,
Pheromones.
Some have specialized scent scales or other structures.
Vision is well developed in butterflies,
And most species are sensitive to the ultraviolet spectrum.
Many species show sexual dimorphism in the patterns of UV reflective patches.
Color vision may be widespread,
But has been demonstrated in only a few species.
Some butterflies have organs of hearing,
And some species make stridulatory and clicking sounds.
Many species of butterfly maintain territories and actively chase other species or individuals that may stray into them.
Some species will bask or perch on chosen perches.
The flight styles of butterflies are often characteristic,
And some species have courtship flight displays.
Butterflies can only fly when their temperature is above 27 degrees Celsius or 81 degrees Fahrenheit.
When it is cool,
They can position themselves to expose the underside of the wings to the sunlight to heat themselves up.
If their body temperature reaches 40 degrees Celsius or 104 degrees Fahrenheit,
They can orient themselves with the folded wings edgewise to the sun.
Basking is an activity which is more common in the cooler hours of the morning.
Some species have evolved dark wing bases to help in gathering more heat,
And this is especially evident in alpine forms.
Butterflies have appeared in art from 3,
500 years ago in ancient Egypt.
In hunting scenes,
Butterflies were sometimes included in a way that suggested life,
Freedom,
And the strength to escape capture,
Creating a balance to scenes concerned with death and upholding Maat.
They also were suggestive of regeneration or rebirth and protection.
Certain butterflies,
Such as the tiger butterfly,
May have been associated with solar deities,
Particularly Ra.
The tiger butterfly also would have a particular resemblance to the Ankh due to its black body and wingtips that was likely noted by the ancient Egyptians.
Butterflies may also have been understood as one of the deceased guides in the afterlife.
According to Lafcadio Hearn,
A butterfly was seen in Japan as the personification of a person's soul,
Whether they be living,
Dying,
Or already dead.
One Japanese superstition says that if a butterfly enters one's guest room and perches behind the bamboo screen,
The person whom one loves is coming to visit.
Diderot Encyclopédie cites butterflies as a symbol for the soul.
A Roman sculpture depicts a butterfly exiting the mouth of a dead man,
Representing the Roman belief that the soul leaves through the mouth.
In line with this,
The ancient word for butterfly is Psyche,
Which primarily means soul or mind.
According to Mircea Eliade,
Some of the Nagas of Manipur claim ancestry from a butterfly.
In popular Burmese culture,
The butterfly is symbolic of the soul or consciousness of a person.
During the transitory period after death,
The Burmese believe that the butterfly soul becomes a wandering spirit in search of a new corporeality medium.
In some cultures,
Butterflies symbolize rebirth.
Several American states have chosen an official state butterfly.
In evolutionary biology,
Mimicry is the evolved resemblance of an organism to something else,
Often another organism of a different species.
Mimicry may evolve between different species,
Or between individuals of the same species.
In the simplest case,
As in Batesian mimicry.
A mimic resembles a model,
So as to deceive a dupe.
All three being of different species.
A Batesian mimic,
Such as a hoverfly,
Is harmless,
While its model,
Such as a wasp,
Is harmful,
And is avoided by the dupe,
Such as an insect-eating bird.
Birds hunt by sight,
So the mimicry in that case is visual.
But in other cases mimicry may make use of any of the senses.
Most types of mimicry,
Including Batesian,
Are deceptive,
As the mimics are not harmful.
But Mullerian mimicry,
Where different harmful species resemble each other,
Is honest.
As when species of wasps and of bees all have genuinely aposematic warning coloration.
More complex types may be bipolar,
Involving only two species,
Such as when the model and the dupe are the same.
This occurs,
For example,
In aggressive mimicry,
Where a predator in wolf and sheep's clothing style resembles its prey,
Allowing it to hunt undetected.
Mimicry is not limited to animals.
And Poojanian mimicry,
An orchid flower is the mimic resembling a female bee,
Its model.
The dupe is the male bee of the same species,
Enabling it to transfer pollen so the mimicry is again bipolar.
In AutoMimicry,
Another bipolar system,
Model and Mimic are the same.
As when blue lyceanid butterflies have tails or eye spots on their wings that mimic their own heads,
Misdirecting predator dupes to strike harmlessly.
Many other types of mimicry exist.
