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.Marschalek, D. A., Faulkner, D. K., & Deutschman, D. H. (2019). Ecology of the threatened Harbison's dun skipper (Euphyes vestris harbisoni) for conservation efforts within a habitat conservation plan. Journal of Insect Conservation, 23(2), 331–339. https://doi.org/10.1007/s10841-019-00128-y Euphyes vestris inhabits multiple environments, including open fields, oak woodlands, and riparian wetlands.Heitzman, J. R. (1964). Early stages of Euphyes vestris. The Journal of Research on the Lepidoptera, 3(3), 151–153. https://doi.org/10.5962/p.333482 There are currently four recorded subspecies of Euphyes vestris, three of which have been identified across eatern, western, and mountainous regions of North America. These subspecies are E. v. metacomet, E. v. vestris, and E. v. kiowah. The fourth subspecies, Euphyes vestris harbisoni, known as the Harbison's dun skipper is geographically restricted to southern California and northern Mexico.
The dun skipper, Euphyes vestris, is categorized within the genus Euphyes, a known group of ten closely related skippers found in North America.Miller, L. D., Harvey, D. J., & Miller, J. Y. (1985). Notes on the genus Euphyes, with description of a new subspecies (Lepidoptera: Hesperiidae). Florida Entomologist, 68(2), 323–335. 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 relies on sedges, which are plants in the family Cyperaceae, as host plants for its larval development.
Taxonomy Euphyes vestris belongs 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 specific environments where certain 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 throughout North America.
Subspecies 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)
Physical description
Adults Adult E. vestris are physically characterized as medium-sized skippers. They often have a wingspan of 25-35 mm, with the largest subspecies, E. v. harbisoni, known to have an average wingspan of 30-35 mm.Marschalek, D. A., & Deutschman, D. H. (2018). San Diego County Harbison's dun skipper (Euphyes vestris harbisoni) habitat conservation and management plan. San Diego State University, prepared for the San Diego Association of Governments. Male and female adults are additionally characterized by their brown appearance, with golden hairs 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 light spots on their forewings, as well as a faint band on their hindwings.
Eggs 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 middle section of their host plant leaves.
Larval description Detailed accounts of the larval description were provided by Heitzman in 1964 in the article "The Early Stages of Euphyes vestris" published 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 appearing paler. The body is also 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 has a pale green body with faint white coloring. 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 molt 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 visible dots. The head is described as caramel brown with a cream band running across the outer edge. Additionally, there is a black oval spot located in 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 velvety black oval spot present near the upper center of the face. The jaws of the larvae are dark brown and black.
Pupa 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. During pupation, the pupa position is positioned upright with a short silk structure extending 10 mm in front of it.
Geographical distribution E. vestris is known to have a large geographical distribution, as it can be found across the United States and southern Canada. However, although the species as a whole is broadly distributed across North America, specific subspecies are restricted to specialized regions.
Specifically, the subspecies Euphyes vestris harbisoni is very restricted and is found only in southern California and northern Mexico. Within California, it is most commonly found in San Diego County, in addition to western regions of Riverside County. Recent surveys examining 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 had previously been recorded. Of the 39 known locations, 33 were publicly accessible, while the other six were located in restricted private areas. Among the accessible sites, 22 still 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. These surveys show that the geographic distribution of the subspecies is concentrated within San Diego, Orange, and Riverside counties. 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 confirmed, the host plant alone is not enough to support the geographic distribution of the species. Other environmental factors such as moisture, shade, and vegetation can also contribute to whether the populations can survive in a location.
Habitat
Habitat of broader species 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.
Habitat of E. v. harbisoni The habitat of the harbisoni subspecies has been more thoroughly researched compared to other subspecies, and it has been found that this subspecies is a habitat specialist. Specifically, 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 shaded oak trees within riparian oak woodlands. Additionally, surveys have shown that San Diego sedge is associated with riparian oak woodlands, which explains why this subspecies is found near this environment as its primary habitat.
Additionally, it has been found that San Diego sedge is located near flowing water, which means that E. v. harbisoni will also often be found there. In addition to its host plant, environmental conditions also help explain the habitat preferences of harbisoni. Based on GIS habitat analysis, three critical factors were found to influence habitat preference: maximum temperature in June, actual evapotranspiration in July, and elevation.Lyons, A. R., Faulkner, D. K., Deutschman, D. H., & Marschalek, D. A. (2024). Evaluating the status and habitat preferences of the threatened skipper, Euphyes vestris harbisoni, in southern California, USA. Journal of Insect Conservation, 28(6), 1285–1296. https://doi.org/10.1007/s10841-024-00623-x When these conditions 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.
Life cycle
Egg 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.
Larvae Once the eggs have hatched, the larvae immediately start consuming their host plant to obtain energy for growth and development. As the larvae continue to eat and grow, they gradually develop through successive instars, eventually building 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 each, whereas the final instar lasts 12 days.
Pupae Pupation of E. vestris occurs within the shelter that the larvae build earlier in development, called a hibernaculum. Before pupation, however, the upper part of the shelter is closed off, and the pupal stage takes 18–21 days.
Adults 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 the leaves of their host plants, allowing the life cycle to restart.
Host plants