Dun Skipper (Euphyes vestris)

Euphyes vestris
Euphyes vestris metacomet
Conservation status
Secure (NatureServe)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Clade:	Pancrustacea
Class:	Insecta
Order:	Lepidoptera
Family:	Hesperiidae
Genus:	Euphyes
Species:	E. vestris
Binomial name
Euphyes vestris (Boisduval, 1852)[2]
Synonyms
Hesperia vestris Boisduval, 1852 Hesperia ruricola Boisduval, 1852 Euphyes ruricola Pamphila osceola Lintner, 1878 Pamphila californica Mabille, 1883 Hesperia metacomet Harris, 1862 Pamphila rurea Edwards, 1862 Hesperia osyka Edwards, 1867 Hesperia baeis Scudder, 1889 (nomen nudum)

Euphyes vestris, commonly referred to as the dun skipper, is a butterfly belonging to the Hesperiidae family. It appears as a brown, medium sized butterfly found across the United States and southern Canada. Euphyes vestris has been known to inhabit multiple environments, including open fields, oak woodlands, and riparian wetlands. There are currently four recorded subspecies of Euphyes vestris, three of which have been identified inhabiting a wide range of regions including eatern, western, and mountainous regions of North America. These species are E. v. metacomet, E. v. vestris, and E. v. kiowah. The fourth subspecies, Euphyes vestris harbisoni, is geographically restricted to southern California and northern Mexico.

The dun skipper, Euphyres vestris, is categorized within the genus Euphyes, a known group of ten closely related skippers found in North America. Species belonging to this genus live in environments with high humidity, such as swampy habitats, and occur in small populations. Across its subspecies it has been recognized that E.vestris is reliant to sedges, plants in the family Cyperaceae, which serve as host plants for its larvae. As previously notes because E. vestris is strongly dependent on its habitat to maintain its small population size in addition to host plants for larvae development it is susceptible to habitat loss caused by climate change.

Euphyes vestris belong to the order Lepidoptera and the family Hesperiidae. The genus Euphyes includes ten identified species located within North America. Species in this genus are categorized as habitat specialists, which means they are found in certain environments where specific conditions are met. Many Euphyes species live in moist or swampy habitats and occur in isolated populations.

Euphyes vestris was first identified by Boisduval in 1852 and is commonly found within North America.

Adult E. vestris are physically characterized as medium sized skippers. They often have a wingspan of 25-35mm, with the largest subspecies, E. v. harbisoni, known to have an average wingspan of 35mm. Male and female adults are additonally characterized by their brown apperance, with golden hairs protruding on their heads.

It is possible to differentiate the sexes of this species by their wing patterns. Males have a distinctive black stigma on their forewings, with additional orange bordering. Females do not have a black stigma, but instead show two ight spots on their forewings, as well as a feint band on their hindwings.

The eggs of E. vestris are observed as pale green and dome shaped when initially laid. As they mature, fertilized eggs develop red spots on the top, in addition to a red band around the center of the egg. Females have been described as laying eggs one at a time on the midway spot of their host plant leaf.

Detailed accounts of the larval description were provided by Heitzman in 1964 in the publication "The Early Stages of Euphyes vestris" in the Journal of Research on the Lepidoptera.

First instar: Once hatched, the larva consumes the majority of its eggshell. The body of the newly hatched larva is yellow, with multiple segments presenting a paler tone. The body additionally is covered with white hairs, with the last segment notably containing more hairs. The head of the larva is brown with black mandibles.

Second instar: After the first shedding of the outer skin, the larva presents a pale green body with feint white color. It also has black bristles located along the body. The prothoracic shield is described as "jet black", and there is a visible black dot near the first spiracle. In contrast to the first instar, the head is pale orange with dark brown mandibles and brown spots.

Third instar: The next shed in the larva's life cycle allows it to present a watery green color. The last abdominal segment is grayish green and surrounded by white hairs. The prothorax is visibly white and contains a shiny black prothoracic shield. The head of the larva is pale orange/brown with notable cream colored vertical stripes. Additionally, there is a dark brown oval spot near the face. The head is surrounded by yellow bristles.

Fourth instar: The larva is bright green with many horizontal marks across the body. The prothoracic shield is predominantly white near the top, with thin black lines along the sides. The first spiracle contains a large black dot while other spiracles do not contain any. The head is describes as caramel brown with a cream and running across the outer edge. Additionally, there is a black oval spot located tm the center of the face.

Final instar: The larva is pale transparent green with a white appearance attributed to the many white marks present on the body. Each spiracle contains a black dot, with a larger dot present on the first spiracle. The back of the head is visibly black, while the remaining portions are brown. There is a velvet black oval spot present near the upper center of the face. The jaws of the larva are dark brown and black.

The pupae of E. vestris are visibly pale, with green undertones on the abdomen, while the wing case, and thorax appear yellow/green. The spiracles of the pupa are dark brown. Additionally, the head contains red bristles. It is important to note that during pupation, the pupa position is upright and it has 10mm of silk in front of it.

E. vestris is known to have a large geographical distribution, as it can be found across the United States and southern Canada. In contrast, although the species as a whole can be identified broadly across North America, many of the subspecies can only be located in specialized regions.

Specifically, the subspecies Euphyes vestris harbisoni is very restricted and can only be found in southern California and northern Mexico. Within California, it is most commonly found in San Diego County, in addition to western region of Riverside County. Recent surveys confirming the geographic distribution of this subspecies have shown a decline in its geographical distribution. At the time these surveys were conducted, from 2013 to 2018, there were 39 known sites where these butterflies were known to exist from past data. Of the 39 known locations, 33 were publicly accessible, while the other six were located in restricted private areas. Among these locations, 22 sites supported the population, while 10 sites were found to no longer support the population. The remaining eight sites were classified as unknown because they were located on private property. This survey show that the geographic distribution of the subspecies is found within San Diego, Orange County, and Riverside County. Additionally, these surveys found many of the host plants in other parts of San Diego, but the dun skippers were not identified. This is important because it shows that although the presence of the host plant was verified, the host plant alone is not enough to support the geographic distribution of the species, and there are other factors that contribute to the support of their population.

Most subspecies of E. vestris have been noted to live across North America in fields, waste areas, and habitats where sedge plants are present. The species has also been known to be attracted to flowers in the genus Mentha, Apocynum, and Asclepias.

The habitat of the harbsoni subspecies has been more thoroughly researches, and it has been found that this subspecies is a habitat specialist in contrast to other subspecies. Specially, the habitat of the harbisoni subspecies has been associated with riparian oak woodlands within San Diego County. This subspecies relies heavily on the presence of San Diego sedge, Carex spissa, because it serves as the larval host plant. The sedge can be found to "grow along creek beds and drainage areas beneath shade oak trees". Additionally, surveys have shown that San Diego sedge is associated with riparian oak woodlands, which explain why this subspecies sis found near this environment as its primary habitat.

Additionally, it has been found that this species of sedge is located near flowing water, which means that E. v. harbisoni will also often be found there. In addition to its host plants, environmental conditions also help explain the habitat preferences of the harbisoni. Based of GIS habitat analysis, three critical factors were found to influence habitat preference: maximum temperature in June, actual evapotranspiration in July, and elevation. When these condition become too harsh, the population of the species declines. This means that E. v. harbisoni prefers habitats where these three factors are at optimal levels for its survival.

The life cycle of E. vestris starts with the egg stage, in which the adult female lays eggs one at a time on the host plant. The eggs are described as pale yellow. For the subspecies E. v. harbisoni, the eggs are known to be laid on San Diego sedge leaves. For the subspecies E. v. metacomet, females place eggs on host plants such as Carex heliophilia, in addition to other sedge species.

Once the eggs have hatched, the larvae immediately start consuming their host plant to gain strength. As the larvae continue to eat and grow they gradually shed through successive instars, through which they eventually build a protective shelter called a hibernaculum. The foundation of these shelters is their host plant leaves in addition to silk. This shelter serves as a safe space for the larvae, which is used when they are not feeding. The first four instars of the species last around seven days, whereas the last one is known to last 12 days.

Pupation of E. vestris occurs within the shelter they build as larvae called hibernacula. Before pupation, however, the upper part of the shelter is closed off, and the pupal stage takes 18-21 days.

The adults of E. vestris commonly emerge during spring and summer. In the subspecies E. v. harbisoni, "adult flight season is known to last from May 15 to July 16". The adults are known to be active during the warmer parts of the day. Their activity is correlated with temperature, which also influences how likely they are to fly. During the adult stage, females reproduce by laying eggs one at a time on their leaves of their host plants, allowing the life cycle to restart.

The host plants of members of the E. vestris family are the sedge plant family, Cyperaceae. However, the specific specie of sedge plant is dependent on the subspecies in addition to the region. For the eastern subspecies, E. v metacomet, it was discovered that they are able to successfully host on the plant species yellow nutsedge, Cyperus esculentus. This specific species of plant is found in damp areas located near roadsides. Additionally, for the subspecies E. v. harbisoni, the larval host is located in San Diego and is called San Diego sedge, Carvex spissa, most commonly found in riparian oak woodlands. The host plants are very sensitive to climate events, in which events such as drought can make then unusable and uninhabitable for larval usage. This is something that should be taken into consideration when viewing conservation because to conserve this species, it is not only important to protect the larvae but also the host plants used to lay eggs.

Studies have examined the reproduction of E. vestris by looking at spermatophore in females. Spermatophores are structures that are transferred by males during mating. Specifically, in butterflies, a successful mating allows the female to have a spermatophore within her reproductive tract.

In the publication Mating Frequency in Natural population of Skippers and Butterflies ad Determined by Spermatophore Counts, it was found that the average spermatophore count within a mated female was 1.45. This result shows that E. vestris has an intermediate mating pattern, meaning that it falls between the two extremes of only mating once or mating multiple times. It was also pointed out in this article that mating frequency can be related to this species' population density., meaning that in dense populations, females are likely to mate less often since there are more males available, but in less dense populations, they will mate more often since there are fewer males.

Additionally, reproduction is also dependent on the survival of the host plant because females lay eggs on plants such as San Diego sedge for E. v. harbisoni. Therefore, reproduction dpends on whetehr the host plant is healthy.

• Euphyes vestris vestris (California)
• Euphyes vestris metacomet (Harris, 1862) (from Alberta east through the southern parts of Saskatchewan, Manitoba, Ontario, Quebec and New Brunswick, southeast through Montana, South Dakota, Kansas, Missouri, Arkansas, Mississippi and Louisiana, and eastward to the Atlantic coast)
• Euphyes vestris kiowah (Reakirt, 1866)
• Euphyes vestris harbisoni Brown & McGuire, 1983 (California)

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