Variable Checkerspot
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The variable checkerspot or Chalcedon checkerspot (''Euphydryas chalcedona'') is a
butterfly Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...
in the family
Nymphalidae 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 ha ...
. It is found in western North America, where its range stretches from
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
in the north to
Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
in the south and extends east through the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
into
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
,
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
,
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
and
Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
. The butterfly is usually brown or black with extensive white and yellow checkering and some red coloration on the dorsal wing. Adult wingspan is . Adult butterflies feed on
nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
from
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
s while
larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...
feed on a variety of plants including snowberry (''
Symphoricarpos ''Symphoricarpos'' is a small genus of about 15 species of deciduous shrubs in the family Caprifoliaceae. With the exception of the Chinese coralberry, '' S. sinensis'', which is indigenous to western China, all species are native to North and C ...
''), paintbrush (''
Castilleja ''Castilleja'', commonly known as paintbrush, Indian paintbrush, or prairie-fire, is a genus of about 200 species of Annual plant, annual and Perennial plant, perennial mostly herbaceous plants native to the west of the Americas from Alaska sout ...
''), ''
Buddleja ''Buddleja'' (; ''Buddleia''; also historically given as ''Buddlea'') is a genus comprising over 140 species of flowering plants endemicity, endemic to Asia, Africa, and the Americas. The generic name bestowed by Carl Linnaeus, Linnaeus posthu ...
'', ''
Diplacus aurantiacus ''Diplacus'' is a genus of flowering plants in the family Phrymaceae, which was traditionally placed in family Scrophulariaceae. It includes 49 species native to the western United States and northwestern Mexico. Most prefer dry and rocky areas. ...
'' and ''
Scrophularia californica ''Scrophularia californica'' is a flowering plant in the figwort family which is known by the common names California figwort and California bee plant. It is native to the western United States, including many habitats in California, and in Bri ...
''. During the breeding period, males congregate around larval host plants to encounter females. Males court female butterflies via physical displays.Rutowski, Ronald L., and George W. Gilchrist. "Courtship, Copulation and Oviposition in the Chalcedon Checkerspot,(Lepidoptera: Nymphalidae)." Journal of Natural History 21.5 (1987): 1109-117. Successful courtship leads to copulation, when the male deposits a nutrient-rich
spermatophore A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especiall ...
in the female. In addition, males also secrete a
mating plug A mating plug, also known as a copulation plug, vaginal plug, sperm plug, or sphragis (Latin, from , "a seal"), is a gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract, such as the vag ...
during copulation that hinders the ability of females to mate with other males. Pregnant females look for host plants like ''
Diplacus aurantiacus ''Diplacus'' is a genus of flowering plants in the family Phrymaceae, which was traditionally placed in family Scrophulariaceae. It includes 49 species native to the western United States and northwestern Mexico. Most prefer dry and rocky areas. ...
'' that are close to nectar sources when they lay their eggs. The larvae that emerge from the eggs feed and live on these host plants, some of which have developed strategies to deter larvae from eating their leaves. After moving to a darker and more secluded site, larvae enter
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 ...
, emerging between January and March with
pupation 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 ...
usually beginning in April. The variable checkerspot is a potential food source for many avian predators. Due to a larval diet rich in
catalpol Catalpol is an iridoid glucoside. This natural product falls in the class of iridoid glycosides, which are simply monoterpenes with a glucose molecule attached. Natural occurrence First isolated in 1962, catalpol was named for plants in the ge ...
, this butterfly has developed a strategy of unpalatability to deter avian predation.Lincoln, David E., and Harold A. Mooney. "Herbivory on Diplacus Aurantiacus Shrubs in Sun and Shade." Oecologia 64.2 (1984): 173-76. In addition, coloring plays a part in the defense strategy of the butterfly; intense red coloration deters predators from attacking them.


Taxonomy

The variable checkerspot is a member of the
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
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 ...
, which contains the butterflies and the moths. It belongs to the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Nymphalidae 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 ha ...
, which also includes the tortoiseshells and the
admirals Admiral is one of the highest ranks in many navies. In the Commonwealth nations and the United States, a "full" admiral is equivalent to a "full" general in the army or the air force. Admiral is ranked above vice admiral and below admiral of ...
. The variable checkerspot is part of the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''
Euphydryas ''Euphydryas'' is a genus of Nymphalidae butterflies. Species References Further reading * Glassberg, Jeffrey ''Butterflies through Binoculars: The West'' (2001) * Guppy, Crispin S. and Shepard, Jon H. ''Butterflies of British Columbia'' ( ...
'', which contains other checkerspot butterflies like ''
Euphydryas editha Edith's checkerspot (''Euphydryas editha'') is a species of butterfly in the family Nymphalidae. It is a resident species of western North America and among the subspecies, entomologists have long been intrigued by their many phenotypic variation ...
'' and ''
Euphydryas phaeton The Baltimore checkerspot (''Euphydryas phaeton'') is a North American butterfly of the family Nymphalidae. It has been the official state insect of the U.S. State of Maryland since 1973. The Baltimore checkerspot was named for the first Lord B ...
''. There are ten
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
of ''Euphydryas chalcedona''. Additional information is required to determine the
conservation status The conservation status of a group of organisms (for instance, a species) indicates whether the group still exists and how likely the group is to become extinct in the near future. Many factors are taken into account when assessing conservation ...
of some subspecies.


Description

The variable checkerspot is usually brown-black with extensive yellow, red and white spots on the dorsal wing. Their underside usually contains yellow and orange bands. However, as its name suggests, the butterfly is highly variable in appearance. Dorsal color can range from a brick-red background with brown and yellow markings in Sierra populations to yellow and black in northern Californian populations. Adult wingspan is . The species is visually similar to ''
Euphydryas anicia ''Euphydryas anicia'', the anicia checkerspot, is a species in the family of butterflies known as Nymphalidae. It was first described by Edward Doubleday in 1847 and it is found through Mid to Western North America and all of Southern British Co ...
,'' with the only notable difference being their male genitalia''.''


Distribution and habitat

The variable checkerspot is found across western North America, ranging from
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
in the north to
Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
and
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 ...
in the south. Its habitat is bounded to the west by the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
and it extends east past the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
into
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
,
Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
,
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
and
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
. The butterfly's habitat encompasses a large variety of environments, including sagebrush flats, desert hills, prairies, open forests and alpine tundra.


Life cycle

The variable checkerspot lays its eggs in clusters. Pre-
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 ...
larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...
often move to fresher parts of the plant in which they are laid to secure a better food source. Before they enter diapause, the larvae leave the food plant to seek better
dormancy Dormancy is a period in an organism's Biological life cycle, life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolism, metabolic activity and therefore helps an organism to conserv ...
sites such as under the bark of dead branches, in the hollow stems of dried weeds and in rock crevices. During diapause, some larvae are able to wake up and feed before re-entering dormancy. The larvae emerge from diapause between late January and mid-March. However, in high elevations, larvae can hibernate for several years.
Pupation 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 ...
begins in early to middle April and the adult flight season begins between mid-April and May and continues into June. The adult variable checkerspot has a life span of around 15 days.O'Brien, Diane M., Carol L. Boggs, and Marilyn L. Fogel. "Making Eggs from Nectar: The Role of Life History and Dietary Carbon Turnover in Butterfly Reproductive Resource Allocation." Oikos 105.2 (2004): 279-91.


Breeding


Mate location

Male mate-location strategies in the variable checkerspot are primarily determined by female distribution in an area. For species like ''E. chalcedona'' that
pupate 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 the ...
densely on larval food plants, females are most densely distributed near these plants. In addition, virgin females, the most desirable
mates Mates is an English surname, and may refer to: * Mates (born 1964), British newsreader and journalist * Michael Mates (born 1934), British politician * Frederick S. Mates, founded the Mates Investment Fund in 1967 that crashed in the bear market ...
for male butterflies, are most often found near larval host plants. Male mate-locating behavior has evolved to maximize encounters with virgin females and thus male variable checkerspot butterflies thus primarily use larval food plants as encounter sites for possible female mates. Males both perch near food plants and fly around them in order to look for fertilizable females.Rutowski, Ronald L., George W. Gilchrist, and Barbara Terkanian. "Male Mate-locating Behavior in Euphydryas Chalcedona (Lepidoptera: Nymphalidae) Related to Pupation Site Preferences." Journal of Insect Behavior 1.3 (1988): 277-89.Rutowski, Ronald L. "The Evolution of Male Mate-Locating Behavior in Butterflies." The American Naturalist 138.5 (1991): 1121-139. Male butterflies do not stay in one encounter site for long and do not typically defend the territory of their encounter site. Males depend on
visual The visual system is the physiological basis of visual perception (the ability to detect and process light). The system detects, transduces and interprets information concerning light within the visible range to construct an image and buil ...
rather than chemical cues to locate females.


Courtship

To start
courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage or committed romantic, ''de facto'' relationship. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marri ...
, the male arrives in the vicinity of a fertilizable female, who quickly moves to the ground or to vegetation. The male follows and attempts to
copulate Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...
with the female by curling his abdomen forward along the side of his body and inserting it between the female's hindwings. At this point, the female may stay still or flutter her wings and move away. If the female moves away, the male follows her and repeats his attempts to copulate. Only when the female stops and remains motionless can the male successfully copulate with her. In unsuccessful courtships, the female either flies away or rapidly flutters her wings until the male departs. Courtship in the variable checkerspot lacks an obvious male display such as the release of chemical signals by the male. Successful courtship in ''E. chalcedona'' lasts about a minute.


Copulation

Once a male has successfully courted a female, the pair begins to copulate. Copulations typically last around an hour, although prolonged copulations as long as six hours have been observed in the wild. During copulation, the male fills the female's bursa copulatrix with material that forms the
spermatophore A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especiall ...
, a nutrient-rich complex that delivers the sperm to the female. On average, the spermatophore represents 7% of the male’s body weight. This weight proportion is similar to that of other butterflies whose
mating systems A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mating, mate under which circumstances. Reco ...
resemble that of the variable checkerspot, indicating that males in these species give roughly similar nutrient investments to their mates. While producing the spermatophore is a costly endeavor for the male, evidence indicates that the spermatophore is not a
paternal investment In biology, paternal care is parental investment provided by a male to his own offspring. It is a complex social behavior in vertebrates associated with animal mating systems, life history traits, and ecology. Paternal care may be provided in co ...
in offspring. In fact, the size of the spermatophore produced by a male is not correlated with the reproductive success of his female mate in terms of the number of eggs she lays and the percentage of those eggs that hatch. Paternal investment via the spermatophore in ''E. chalcedona'' may be less important than in other butterfly species due to the severe time constraints on female variable checkerspot butterflies to lay their eggs quickly. Because of these constraints, female butterflies emerge with all
oocytes An oocyte (, oöcyte, or ovocyte) is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ger ...
present and some eggs already containing
yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...
, thus limiting the role of the
spermatophore A spermatophore, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especiall ...
in promoting female
reproductive success Reproductive success is an individual's production of offspring per breeding event or lifetime. This is not limited by the number of offspring produced by one individual, but also the reproductive success of these offspring themselves. Reproduct ...
.Jones, Kristina M., Francois J. Odendaal, and Paul R. Ehrlich. "Evidence against the Spermatophore as Paternal Investment in Checkerspot Butterflies (Euphydryas: Nymphalidae)." American Midland Naturalist 116.1 (1986): 1-6.


Harassment

Female availability is an important factor in determining mating systems. Because the breeding period of the variable checkerspot is brief, female availability is limited by time as well as by space. Male butterflies in other species with brief female availability have developed strategies that ensure quick access to fertilizable females, leading to high levels of male harassment. This sexual harassment has led mated females in other species of butterfly to gather in areas of lower male density, since consistent harassment could negatively impact the time females have to search for food sources and lay eggs. However, this potential for harassment does not influence egg distribution by mated females in ''E. chalcedona''. Variable checkerspot eggs are always distributed around good larval food sources, regardless of the level of male harassment at those sites.Odendaal, F. J., Y. Iwasa, and P. R. Ehrlich. "Duration of Female Availability and Its Effect on Butterfly Mating Systems." The American Naturalist 125.5 (1985): 673-78.


Mating plugs

Female butterflies regularly mate more than once. Females can internally store the
sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...
of many males at one time, but the sperm of the most recently mated male is the one that usually
fertilize Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or off ...
s the female. While seeking out multiple mates can lead to increased
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
exposure and
predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
risk, female butterflies can often benefit from
remating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reprodu ...
by receiving more material resources from males and increasing the
genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species. It ranges widely, from the number of species to differences within species, and can be correlated to the span of survival for a species. It is d ...
of their offspring. Virgin females are found to engage in remating behavior more frequently than recently mated females. Remating behavior by a female harms her most previous mate, who could lose his paternity if another male's sperm fertilizes the female. Thus, after males produce the spermatophore, they pass an additional gland secretion that spills out of the female's copulatory opening, forming a
mating plug A mating plug, also known as a copulation plug, vaginal plug, sperm plug, or sphragis (Latin, from , "a seal"), is a gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract, such as the vag ...
that hardens within a few hours of copulation. As the female variable checkerspot has two genital openings, this secretion does not impact
oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...
ability. The mating plug protects the male's paternity by acting as a mechanical barrier to reinsemination by preventing other males from penetrating the female.Dickinson, Janis L., and Ronald L. Rutowski. "The Function of the Mating Plug in the Chalcedon Checkerspot Butterfly." Animal Behaviour 38.1 (1989): 154-62.


Group behavior

During the flight season, large groups of variable checkerspot butterflies can be found across western North America. Individual butterflies are capable of recognizing suitable areas rich in larval food plants and do not usually linger in other parts of the landscape. This leads to populations of butterflies that are small, isolated and clearly separated from other populations. Females do not fly as much as males, who frequently fly around their habitats and perch in open areas while searching for female mates. Flight times for the variable checkerspot vary regionally. Usually, the flight season lasts from April to June in California and Oregon, while it normally takes place from June to July farther north and in higher elevations.


Diet

The diet of the variable checkerspot changes dramatically with development: the larva has an
herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...
diet consisting entirely of plants while the adult butterfly feeds exclusively on
nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
.


Larval diet

The principal food source for variable checkerspot larvae are the leaves of the flowering
subshrub A subshrub (Latin ''suffrutex'') or undershrub is either a small shrub (e.g. prostrate shrubs) or a perennial that is largely herbaceous but slightly woody at the base (e.g. garden pink and florist's chrysanthemum). The term is often interch ...
''
Diplacus aurantiacus ''Diplacus'' is a genus of flowering plants in the family Phrymaceae, which was traditionally placed in family Scrophulariaceae. It includes 49 species native to the western United States and northwestern Mexico. Most prefer dry and rocky areas. ...
'' that also usually serve as its host plant. ''D. aurantiacus'' contains large amounts of a leaf
phenolic resin Phenol formaldehyde resins (PF), also called phenolic resins or phenoplasts, are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial synthetic ...
, which helps resist water loss during drought. Laboratory and field studies have shown that increased resin content is negatively correlated to the growth and survivorship of variable checkerspot larvae, indicating that the phenolic resin in ''D. aurantiacus'' plays in important role in deterring larvae from feeding on leaves.Han, Kaiping, and David Lincoln. "The Evolution of Carbon Allocation to Plant Secondary Metabolites: A Genetic Analysis of Cost in Diplacus Aurantiacus." Evolution 48.5 (1994): 1550-563. Another factor in ''D. aurantiacus'' plants that impacts larval growth is leaf
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
content. Unlike resin levels, heightened nitrogen levels are correlated with increased larval growth and survivorship. In a controlled experiment, larva that were fed a diet of fertilized ''D. aurantiacus'' plants, which contained 50% more nitrogen than unfertilized plants, experienced higher survival rates and growth than larvae that fed on unfertilized plants. While leaves with increased nitrogen content are the most attractive for the larvae, they are also the most valuable carbon-gainers for the plant. This leads to the activity patterns of larvae and ''D. aurantiacus'' plants synchronizing. Larvae emerge from
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 ...
as '' D. aurantiacus'' plants start flowering. This is when the plants need the most carbon. The plants then concentrate their resin in their youngest leaves, which contain the largest amount of nitrogen; this resin deterrent forces larvae to feed on less valuable older leaves whose nitrogen content is lower. To maximize their own nutritional benefits, larvae selectively eat leaves with the highest available nitrogen:resin ratio. In addition, larvae exhibit a strong preference for feeding on host plant leaves that have been in the sun compared to leaves that have been in the shade. Another less common host plant for variable checkerspot larvae is ''
Scrophularia californica ''Scrophularia californica'' is a flowering plant in the figwort family which is known by the common names California figwort and California bee plant. It is native to the western United States, including many habitats in California, and in Bri ...
'', which lacks the resin defense system found in ''D. aurantiacus'' and is thus easier for larvae to digest. Larvae that feed on ''S. californica'' grow faster and larger than those that feed on ''D. aurantiacus''. While ''D. aurantiacus'' may not be the most nutritious food for the larvae, it is the most reliable and widespread
host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...
available to the variable checkerspot and is often the plant closest to nectar sources, leading to its role as principal host plant and food source for the larvae.Williams, K. S., D. E. Lincoln, and P. R. Ehrlich. "The Coevolution of Euphydryas Chalcedona Butterflies and Their Larval Host Plants II. Maternal and Host Plant Effects on Larval Growth, Development, and Food-Use Efficiency." Oecologia 56.2-3 (1983): 330-35.


Adult diet

In contrast to the herbivorous diet of the larva, the adult variable checkerspot's main food source is the
nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
it obtains from flowers. In
Jasper Ridge Biological Preserve The Jasper Ridge Biological Preserve is a nature preserve and biological field station formally established as a reserve in 1973. The biological preserve is owned by Stanford University, and is part of the Stanford School of Humanities and Scie ...
in California, an extremely well studied site, the nectar source most frequently used by adult butterflies is ''
Eriodictyon californicum ''Eriodictyon californicum'' is a species of plant within the family Boraginaceae. It is also known as yerba santa (sacred herb), mountain balm, bear's weed, gum bush, gum plant, and consumptive weed.Patricia Kaminski and Richard Katz.Yerba Santa ...
''.


Diet and oviposition

The diet of the adult butterfly has a large impact on the choice of ''D. aurantiacus'' as the
oviposition The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typica ...
site and larval host of the variable checkerspot. Adult butterflies prefer to oviposit on host sites that are close to nectar sources. In the Jasper Ridge site, ''D. aurantiacus'' is the host plant closest to the '' E. californicum'' nectar source. This proximity advantage overcomes its nutritional deficiencies compared to other host plants and leads to it being the principal host plant of variable checkerspot butterflies.Murphy, Dennis D., Marian S. Menninger, and Paul R. Ehrlich. "Nectar Source Distribution as a Determinant of Oviposition Host Species in Euphydryas Chalcedona." Oecologia 62.2 (1984): 269-71.


Predation and defense

The variable checkerspot's main predators are
birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
. Populations of the variable checkerspot, like most
lepidopterans 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 ...
, are usually scarcely distributed and thus direct observation of avian predation on butterflies is rare. One study analyzed the evidence of avian predation on the butterflies by the presence of a large number of detached variable checkerspot wings at a butterfly population center. These detached wings exhibited beak marks and characteristic triangular tears indicating that birds attacked the butterflies and detached their wings before eating the body. In addition to the remains of this successful predation, photographs of variable checkerspot butterflies show some individuals that exhibit beak marks and tears, indicating unsuccessful avian predation attempts. Analysis of the avian predation on the variable checkerspot population has found that predators disproportionately attack female butterflies. This is because attacks are concentrated on butterflies that contain less intense red coloration. The male butterfly exhibits more variation in its coloration than the female, and can be more intensely red colored. This means that on average, females face more attacks than males do. Red serves as a warning color in many species of butterfly, so it is possible that diminished avian predation is linked to this warning signal. Indeed, the pressure exerted on the variable checkerspot by visually hunting avian predators may play an important role in the evolution of its wing coloration and pattern.Bowers, M. D., Irene L. Brown, and Darryl Wheye. "Bird Predation as a Selective Agent in a Butterfly Population." Evolution 39.1 (1985): 93-103.


Defense strategy

The variable checkerspot, like many other butterflies, has developed a defense strategy of unpalatability to birds as a means of resisting predation. In a controlled experiment, would-be avian predators often exhibit head-shaking and beak-wiping behavior after killing a variable checkerspot, characteristic of tasting unpalatable prey. The unpleasant taste of the butterfly is likely due to the presence of iridoid glycoside compounds in the scrophulariaceous plants that make up the majority of its larval diet.Bowers, M. D. "Unpalatability as a Defense Strategy of Western Checkerspot Butterflies (Euphydryas Scudder, Nymphalidae)." Evolution 35.2 (1981): 367-75.


Iridoid glycosides

The main iridoid glycoside found in the diet of variable checkerspot butterflies is
catalpol Catalpol is an iridoid glucoside. This natural product falls in the class of iridoid glycosides, which are simply monoterpenes with a glucose molecule attached. Natural occurrence First isolated in 1962, catalpol was named for plants in the ge ...
. Chemical analysis has shown that the only iridoid glycoside present in adult butterflies is catalpol.Stermitz, Frank R., Maged S. Abdel-Kader, Tommaso A. Foderaro, and Marc Pomeroy. "Iridoid Glycosides from Some Butterflies and Their Larval Food Plants." Phytochemistry 37.4 (1994): 997-99. Because they are essential for the larvae to develop an unpalatable taste to birds, iridoids act as larval feeding stimulants. Given a choice between a diet that contains no additives and one that contains iridoid glycoside compounds, larvae exhibit a preference for the diet containing the extra iridoid compounds, using olfactory cues to sense their presence. The primary host plants of the variable checkerspot are all rich in catalpol compounds, and the presence of these compounds plays a fundamental role in determining choice of host plant when females
oviposit The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...
.Bowers, M. Deane. "The Role of Iridoid Glycosides in Host-plant Specificity of Checkerspot Butterflies." Journal of Chemical Ecology 9.4 (1983): 475-93. This suggests that the variable checkerspot has evolved to use iridoid compounds as female oviposition stimulants as well as larval feeding stimulants.


See also

* ''
Euphydryas editha Edith's checkerspot (''Euphydryas editha'') is a species of butterfly in the family Nymphalidae. It is a resident species of western North America and among the subspecies, entomologists have long been intrigued by their many phenotypic variation ...
''


References


External links

*
Variable checkerspot
Butterflies of Canada {{Taxonbar, from=Q373264 Euphydryas Butterflies of North America Butterflies described in 1847 Aposematic species Lepidoptera of the United States Lepidoptera of Mexico