Epargyreus Clarus
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''Epargyreus clarus'', the silver-spotted skipper, 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 ...
of the family
Hesperiidae Skippers are a group of butterflies placed in the family Hesperiidae within the order Lepidoptera (moths and butterflies). They were previously placed in a separate superfamily, Hesperioidea, but have since been placed in the superfamily Papilion ...
. It is claimed to be the most recognized skipper in North America. occurs in fields, gardens, and at forest edges and ranges from southern Canada throughout most of the United States to northern Mexico, but is absent in the
Great Basin The Great Basin () is the largest area of contiguous endorheic watersheds, those with no outlets to the ocean, in North America. It spans nearly all of Nevada, much of Utah, and portions of California, Idaho, Oregon, Wyoming, and Baja Californi ...
and western
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 ...
. larvae create and reside in unique shelters stuck together with
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 ...
, which do not protect them from predators. Natural predators of the species include
paper wasp Paper wasps are a type of Eusociality, social vespid wasps. The term is typically used to refer to members of the Vespidae, vespid subfamily Polistinae, though it often colloquially includes members of the subfamilies Vespinae (hornets and yel ...
foragers,
sphecid wasp The Sphecidae are a cosmopolitan family of wasps of the suborder Apocrita that includes sand wasps, mud daubers, and other thread-waisted wasps. The name Sphecidae was formerly given to a much larger grouping of wasps. This was found to be p ...
and ''
Crematogaster ''Crematogaster'' is an ecologically diverse genus of ants found worldwide, which are characterised by a distinctive heart-shaped gaster (insect anatomy), gaster (abdomen), which gives them one of their common names, the Saint Valentine ant. Mem ...
opuntiae'' ants. The species is also considered to be a perching species, meaning that adult males compete for territory to attract females. Although is considered to be a pest of a few crop plants such as beans, its pest activity is not serious enough to warrant initiating major control measures.


Geographic range

''Epargyreus clarus'' has a wide distribution throughout North America: it ranges from southern Canada throughout most of the United States to northern Mexico, but is absent from the Great Basin and western Texas.


Habitat

The silver-spotted skipper prefers open ranges where nectar plants are found, such as forest edges, swamps, brushy areas, and
riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...
habitats at lower elevations.


Home range

At night, or on hot or cloudy days, ''Epargyreus clarus'' rests on the underside of a leaf. It hangs upside down, holding its wings together over its back so that its silver spot is exposed. is often restricted by its habitat, preferring to fly in the shade.


Food resources


Caterpillars

''Epargyreus clarus'' caterpillars consume leaves of herbs, vines, shrubs, and trees in the pea family (''
Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...
'') including false indigobush (''
Amorpha fruticosa ''Amorpha fruticosa'' is a species of flowering plant in the legume family Fabaceae, known by several common names, including desert false indigo, false indigo-bush, and bastard indigobush. It is native to North America. Description ''Amorpha f ...
''), American hogpeanut (''
Amphicarpaea bracteata ''Amphicarpaea bracteata'' (hog-peanut or ground bean) is an annual to perennial vine in the legume family, native to woodland, thickets, and moist slopes in eastern North America. Description Leaves have three leaflets and are held alternate ...
''), groundnut (''
Apios americana ''Apios americana'', sometimes called the American groundnut, potato bean, hopniss, Indian potato, hodoimo, America-hodoimo, cinnamon vine, or groundnut (not to be confused with other plants in the subfamily Faboideae sometimes known by that na ...
''), American wisteria (''
Wisteria frutescens ''Wisteria frutescens'', commonly known as American wisteria, is a woody, deciduous, perennial climbing vine, one of various wisterias of the family Fabaceae. It is native to the wet forests and stream banks of the southeastern United States, w ...
''), Atlantic pigeonwings or butterfly pea (''
Clitoria mariana ''Clitoria'' is a genus of mainly tropical and subtropical, insect-pollinated flowering pea vines. Taxonomy Naming of the genus This genus was named after the human clitoris, for the flowers bear a resemblance to the vulva. The first referenc ...
''), and the introduced Dixie ticktrefoil ('' Desmodium tortuosum''), kudzu (''
Pueraria montana ''Pueraria montana'' is a species of plant in the botanical family Fabaceae. At least three sub-species (alternatively called varieties) are known. It is closely related to other species in the genus ''Pueraria'' (''P. edulis'' and ''Pueraria pha ...
''), black locust (''
Robinia pseudoacacia ''Robinia pseudoacacia'', commonly known as black locust, is a medium-sized hardwood deciduous tree, belonging to the tribe Robinieae of the legume family Fabaceae. It is native to a few small areas of the United States, but it has been widely pl ...
''), Chinese wisteria (''
Wisteria sinensis ''Wisteria sinensis'', commonly known as the Chinese wisteria, is a species of flowering plant in the pea family (botany), family, native species, native to China, in the provinces of Guangxi, Guizhou, Hebei, Henan, Hubei, Shaanxi, and Yunnan. Gr ...
'') and an assortment of other legumes. Innate host plant preferences confer greater performance on larvae, due to differences in leaf nutrient concentrations. However, preference may be influenced by a larva’s rearing host species. They live in meadows and swamps. Their average size is 2 inches long. Average life span is about 2 months. Their predators are wasps, ants, birds, frogs and spiders.


Adults

Adults use their long tongues to feed on the nectar of a variety of flowers, mud, and animal feces. They almost never visit yellow flowers, favoring those that are blue, red, pink, purple, and sometimes white and cream. These include everlasting pea, common milkweed, red clover, buttonbush, blazing star, and thistles.


Parental care


Oviposition

Females lay a single egg on or occasionally near host plants. They have been reported to oviposit on the least snoutbean ('' Rynchosia minima'').


Life cycle


Eggs

The eggs are green, with red coloration on top.


Caterpillar

Larvae are yellow with transverse subdorsal black stripes. The first thoracic segment is black, has a brown prothoracic shield, and is significantly thinner than its adjacent organs – the head and second thoracic segment. The head is described as black or reddish brown with two large, prominent anterior orange spots, which mimic eyes. The three true legs and midabdominal false legs are all bright orange.


Shelter building

All larval instars of ''Epargyreus clarus'' build shelters on their host plant. They build about five shelters throughout larval growth and development in four distinct styles. These are constructed from instinct and are unique to larval size. The first, second, and third instars make a simple, invariant structure that requires two incisions in the leaf and silk to fold over the flap created. Shelters are typically built on the apical portion of the leaflet. One study of larvae in the Washington D.C. area defined five steps of shelter building: # ''Site selection'': Larvae traverse across the entire leaf, following major veins and swinging their heads to create a single silk trail. # Silk template: A thick, visible mat of silk outlines the intended incisions and ultimately becomes the ceiling of the leaf house. The larvae keep their posterior end on the template at all times. # ''First cut'': The first cut follows the silk template on the perimeter nearest the leaf apex. The larvae often interrupt chewing cuts in order to deposit silk at the terminus. The first cut is completed in about 6 to 7 segments. At the end, the larva makes a U-turn motion so that its position relative to the leaf surface and template margins remains the same while facing the opposite direction. # ''Second cut and notch'': The second cut follows the silk template on the edge closest to the base of the leaflet and is completed in about 2 to 4 segments. The first segment curves inwards, is made in a single effort and is about 75% the length of the first cut. The next segment is adjacent to the initial segment and continues past the length of the first cut. The juncture between the two segments creates a notch. # ''Folding and securing'': The uncut area between the first and second incisions composes the hinge. The hinge length tends to correspond to larval body length. The larvae lay silk strands along this area, parallel to the cut termini. As the strands contract, the notch creates a pinch, and the leaf flap is pulled over the leaflet plane. The pinch then becomes the peak of the roof and the larva begins to make "guy-wires" that attach the edge of the flap to the leaflet surface. Larvae take breaks of about 30 minutes between each cut and fold. It typically takes less than 2 hours to complete shelter construction. Larvae spend about 95% of their time resting on the ceiling of the shelter. First instar shelters are typically fastened by only about 2 to 4 "guy-wires". In addition, older caterpillars occasionally live in a nest made of multiple leaves connected by silk, especially when using host plants with smaller leaflets. For example, first, second, and third instars can make shelters with one ''Robinia'' leaflet, but the fourth and fifth instars have to use 2–4 or 5 leaflets.


Pupa

Larvae of ''Epargyreus clarus'' pupate throughout the winter. The pupa is dark brown with black and white marks. There are three or more overlapping generations of hibernating pupa in Florida – fewer in the northern regions.


Adult

The adult wingspan ranges from 1.75 to 2.625 inches (4.5 to 6.7 cm). Each forewing is triangular and dark brown with a large yellow-orange medial patch. Male forewings are more pointed than those of females. The hindwings are also dark brown, with a large silver patch on the discal third of the ventral side.


Migration

Adults are diurnal and fly from early to midsummer. They have one brood per year in the North and West, two in the East, and three to four in the Deep South.


Enemies


Predators

Common predators of ''Epargyreus clarus'' include the paper wasp foragers ''
Polistes fuscatus ''Polistes fuscatus'', whose common name is the dark or northern paper wasp, is widely found in eastern North America, from southern Canada through the southern United States. It often nests around human development. However, it greatly prefers a ...
'' and ''
Polistes dominula The European paper wasp (''Polistes dominula'') is one of the most common and well-known species of social wasps in the genus ''Polistes''. Its diet is more diverse than those of most ''Polistes'' species—many genera of insects versus mainly ca ...
'', as well as ''Crematogaster opuntiae'' ants. Studies have found that shelters protect larvae from these predators in lab settings. Shelters delayed or prevented ''Crematogaster opuntiae'' colonies from detecting the larvae. This is likely because of the ants' limited senses, in conjunction with the inhibitory structure of the shelter: they are able to detect a motionless caterpillar only within approximately one body length, and this is further obstructed by the single small opening into the shelter. While wasps in the laboratory setting did spend more time on areas of the leaf damaged by feeding or silk deposition, the larval shelter prevented visual detection and posed a physical barrier. However, shelters did not protect against these predators in the field. Wasps need spend only a few seconds on a leaflet to successfully identify and remove the larva from its shelter. This suggests that shelter identification and larval extraction is a learned ability, perhaps developed through visual or olfactory cues. Other predators include the sphecid wasp '' Stictia carolina'', which sometimes supplies its nests with silver-spotted skipper larvae. Additional predators also often are attracted to the chemical cues from
frass Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter. Definition and etymology ''Frass'' is an informal term and accordingly it is variously used and variously defined. It is derived from the ...
, or insect excrement. ''Epargyreus clarus'' larvae use an anal comb to throw their frass up to 38 body lengths away from them. When disturbed, larvae regurgitate an unpleasant, greenish chemical in defense.


Parasites

larvae are a natural host of ''
Baculovirus ''Baculoviridae'' is a family of viruses. Arthropods, among the most studied being Lepidoptera, Hymenoptera and Diptera, serve as natural hosts. Currently, 85 species are placed in this family, assigned to four genera. Baculoviruses are known ...
''. The advanced stages of this infection cause larvae to feed without resting. Later, they climb to higher and more exposed areas, where they are more conspicuous to predators. Predator attack leaves their infected remains to be absorbed by the surrounding vegetation, which will be consumed by new hosts.


Mating

Instead of receiving ejaculate, a female receives a large
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 ...
from a male for each copulation. Thus, the number of spermatophores a female contains roughly equates to the number of copulations. Generally, when there are more than two spermatophores present in a female, each one’s placement and degree of erosion indicates its age relative to the other. ''Epargyreus clarus'' is particularly resistant to erosion. Once mated, females seem to reject males, at least for some time afterwards.


Male defense of places likely to attract females

Males perch on branches and tall weeds about above the ground, darting out when any insect passes in hopes of finding a receptive ''Epargyreus clarus'' female. When confronted by another conspecific, male movements are swift and acrobatic. This perching behavior is part of a common mate-location strategy in which males compete for places where females are more likely to occur. Females do not engage in this behavior, but may have to fly considerable distances to find mates, depending on the proximity of male territory to their larval development site. The places "defended" by males are roughly the size of a small room and are most likely chosen based on vegetation and topography.


Physiology


Vision

''Epargyreus clarus'' possesses
compound eyes A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...
that lack pigment in the iris region. Each
ommatidia The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part ...
, or single optical unit, has its own unique visual field that spans about 2°. The small visual field can be due to crystalline tracts in the eye that restrict the light to reach the retina only through this path.


Interaction with plants

''Epargyreus clarus'' is known to be a nectar-thief species. An individual nectar thief is an animal that takes nectar from a flower but does not pollinate it while doing so. A species as a whole can be considered a thief species if it does not pollinate a species of flowers during more than 50% of its feedings. Research has found that while foraging on flowers, the butterfly tended to probe the innermost disk florets, which are the male organs, but not make contact with the outermost florets, which are the female organs.


Pest of crop plants

''Epargyreus clarus'' is known to feed on various crop plants such as soybean and kidney bean. However, no large-scale control measures have been taken, as the species' pest activity is not too detrimental.


References

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External links


''Epargyreus clarus'', silver-spotted skipper
on the UF / IFAS Featured Creatures Web site {{Taxonbar, from=Q568157 Eudaminae Butterflies of North America Articles containing video clips Butterflies described in 1775 Taxa named by Pieter Cramer Lepidoptera of the United States Lepidoptera of Mexico Lepidoptera of Canada