Sonora skipper (Polites sonora) COSEWIC assessment and status report: chapter 3
Species Information
Name and classification
Polites sonora (Scudder, 1872) is a butterfly in the skipper family, Hesperiidae. The subspecific status of Canadian populations is uncertain, as noted by Pyle (2002). Canadian populations were assigned to subspecies sonora in Guppy and Shepard (2001), Llewellyn-Jones (1951), McDunnough (1938), and Pyle (2002), and to subspecies siris (W.H. Edwards, 1881) in Dornfeld (1980), Holland (1931), Layberry et al. (1998), Howe (1975), Scott (1986), and Tilden and Smith (1986). Based on existing literature, it is impossible to conclude whether Canadian populations belong to either subspecies sonora or siris.
All populations in the United States east of the Sierra Nevada Mountains have been assigned historically to subspecies utahensis (Skinner, 1911), but recently Austin (1998) described the subspecies flavaventris and longinqua from Nevada. These three names do not apply to Canadian populations.
The Canadian populations may be an undescribed subspecies (Kondla 2003). Regardless of the subspecies-level taxonomy, only one entity exists in Canada and the entire entity is the subject of this status report.
Morphological description
The Sonora Skipper in Canada is an average-sized skipper with a wingspan of 25 to 30 mm (Figure 1). Colour illustrations of Canadian specimens are available in Layberry et al. (1998), Guppy and Shepard (2001), and Kondla (2003). The dorsal wing surface is a combination of rusty orange and brown with blackish wing margins. The ventral surface of the forewings has a black basal patch, some tawny and pale areas in the median portion of the wing, and an olive-green marginal area that is most pronounced at the apex. The ventral surface of the hind wings is olive-green with a distinct semicircular band of pale spots as well as one, linear, pale spot near the wing base. Males have a black, elongated stigma on the forewing. Females are similar to males, except they lack a stigma and are usually larger.
Figure 1. Dorsal view of a male Polites sonorafrom British Columbia.
Some of the immature stages of Polites sonora have been described as follows by Newcomer (1967) from an unstated location in Washington, and hence the subspecies is unknown:
“EGG. – Basal diameter 1.0 mm, height 0.7 mm. Color very light green. Spherical with small flattened base, not flanged. Finely reticulate.
LARVA. – FIRST INSTAR. – Head width 0.6 mm, shiny black. Body length 1.75 mm, creamy white, a few setae on last two segments; cervical shield black.
SECOND INSTAR. – Head width 0.75 mm, black. Body length 3-5 mm, greenish, covered with numerous minute brown dots; cervical shield black.
THIRD INSTAR – Head width 1.0 mm, solid black, punctate. Body length 5 mm, grayish green with many fine black setae and a few longer ones on posterior segment.”
Scott (1992) stated that the egg of subspecies utahensis is pale green when laid but later develops an orangish flush. He described the first and second instar larvae as yellow-cream with a light orange-brown neck and a dark brown collar and head. Scott also noted that the pupa is very similar to that of the Long Dash Skipper, Polites mystic (W.H. Edwards, 1863).
Genetic description
The Guelph Centre for DNA Barcoding has assembled the mitochondrial DNA sequence of cytochrome C oxidase from two specimens of P. sonora collected from the Copper Mountain road near Princeton, British Columbia.