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Volume 29, Number 4

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PYRGUS XANTHUS (HESPERIIDAE): SYSTEMATICS, FOODPLANTS AND BEHAVIOR

James Scott Department of Entomology, University of California, Davis, California 95616

Pyrgus xanthus Edwards has been greatly confused with P. scriptura (Boisduval) and P. ruralis (Boisduval) (Brown et al., 1957; Callaghan & Tidwell, 1972). This paper clarifies the systematic position of xanthus, details its distribution especially in Colorado, and presents brief observations on foodplants, habitat, and adult behavior. I thank F. M. Brown for providing photographs of the types of xanthus, and Scott L. Ellis, C. Don MacNeill, Kilian Roever, Maurice Howard, Glenn R. Scott, Ray E. Stanford, and Samuel Johnson for providing specimens and helpful information.

Systematic relationship. Table 1 and Figs. 1-30 show 35 characters by which one or more of the above three species differs from the others. Genitalic characters are based on 10 individuals of each sex of each species. P. xanthus is clearly very closely related to P. ruralis and much different from P. scriptura. P. xanthus and P. ruralis are apparently completely allopatric, so that xanthus is the allopatric representative of ruralis characterized by the lack of a costal fold and several genitalic and wing pattern characteristics. It seems best at this time to regard xanthus and ruralis as distinct species because of these differences in morphology, and because the costal fold of ruralis possibly emits a pheromone enabling reproductive isolation from xanthus. Further sampling at possible areas of sympatry (they come within about 10 miles of each other in the Douglas-Jefferson Counties area, Colorado) may resolve this question.

The spring brood of P. scriptura has larger white wing spots than later broods (Fig. 5), and was misidentified and figured as xanthus by Brown et al. (1957). Spring brood scriptura are similar to later broods (cf. Table 1) except for several wing pattern characters by which they can be distinguished. I have seen one scriptura from southern Nevada in August with large white wing spots (coll. Ralph Wells), and rarely xanthus lacks the basal dorsal hindwing spot, but usually the two species can be easily separated by wing pattern. A whitish subspecies of P. ruralis from San Diego County, California (Figs. 3-4) has sometimes been called xanthus, but it is identical to ruralis in all the characters listed in Table 1. The only geographic variation in xanthus appears to

Table 1. Differences between Pyrgus scriptura, P. rural

Character

scriptura

ruralis

altitude habitat foodplant number of broods

male costal fold

white spot, base of DHW

fringe HW

ground color of VHW medial spots VHW

marginal crescentic spots VHW

tegumen

4500-8400/ in Colo.

prairie

Malvaceae: Sida hederacea

three (April-May, June-July, August-Sept)

absent

absent

black spots extend only half of fringe

greyish tan

less strongly outlined, less contrasting with ground color

crescents in cells Cui & Cu2 little longer than those anterior, crescents distinct to margin

triangular in dorsal and ventral view

uncus                                        narrow, sinuous, hooked

sclerite at base of uncus         long

6200-10500/ in Colo. openings in coniferous f Rosaceae: Potentilla sp one (March-June)

Table 1. (Continued)

Character

scriptura

ruralis

gnathos

saccus

juxta

aedeagus

valva

pre-ostial membrane ostium bursa

ductus bursa

lamella post-vaginalis (shape somewhat variable)

lateral pre-papillar sclerites (tergum 8?)

a.   shape (somewhat variable)

b.   anterior tooth

absent beyond gnathal bridge

longer

roughly quadrate, with a dorsal flange extending posteriorly

bent near middle, slightly bent near base

long; prong attached dorsally & directed ventroposteriorly with many recurved spines on bulbous tip; A & B narrow, B curved dorsally

no pouch

at anterior edge of lamella postvaginalis

with oval sclerite near ostium

two separate sclerites (rarely connected by weakly scler-otized area), each narrowing laterally terminating in a "foot"

with a falcate ventral neck

very small to almost absent, no neck

strongly curving to a p beyond gnathal brid

short, broadly connecte vinculum

U-shaped with a shallo notch, no flange

bent near distal end, sp shaped basally

shorter; prong attached with oval base and a long spines at end, d anteroventrally; A & B not curved dorsall

with a ventral pouch

anterior to lamella

no sclerite

one sclerite, V-shaped rowed near ostium) usually with two sm anterior arms

roughly quadrate-hexa larger than other tw

small, at end of neck

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Journal of the Lepidopterists' Society

Figs. 1-24. Adults of Pyrgus spp. P. ruralis: 1, $, Coal Creek, Jefferson Co., Colorado; 2, 9, Gregory Canyon, Boulder Co., Colorado; 3, $ and 4, 9, Laguna Mts., San Diego Co., California. P. scriptura: 5, $ (spring form), Scottsbluff, Nebraska; 6, 9, nr. Westcliffe, Custer Co., Colorado. P. xanthus: 7, $, Raton Mesa, Colfax Co., New Mexico; 8, $, nr. Game Ridge, Custer Co., Colorado; 9, 9, Saguache Park, Saguache Co., Colorado; 10, 9, and 11, $, Devil's Hole, Huerfano

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be a slight increase in size in the southern part of its range. The name macdunnoughi (Oberthur) is a synonym of xanthus.

Lectotype and type-locality. W. H. Edwards (1878) described P. xanthus based on several specimens labeled "southern Colorado" collected by Morrison. The Carnegie Museum of Natural History has three male and two female syntypes, and the American Museum has one syntype. F. M. Brown will designate a lectotype male xanthus in the Carnegie Museum. I examined photographs of the lectotype and a female paralectotype taken by Brown; both specimens possess all the wing characters described for P. xanthus in Table 1. I designate the vicinity of Rosita, Custer County, Colorado, as type-locality of xanthus, because Morrison may have collected there (F. M. Brown, pers. comm.) and the species occurs there.

Foodplants. The foodplants of Pyrgus (and relatives Spialia and Muschampsia) are primarily Rosaceae (Potentilla, Rubus, etc.) and Malvaceae, and several species even feed on both families (Higgins & Riley, 1970). Pyrgus scriptura feeds on Sida hederacea (Malvaceae; many larvae were reared to adults by Jerry A. Powell and C. Don MacNeill at Pittsburgh, California) and Sphaeralcea coccinea (Malvaceae; ovipositions at Green Mountain, Jefferson County, Colorado). P. ruralis larvae were found feeding on leaves of several Potentilla spp. in California by C. Don MacNeill (pers. comm.). P. ruralis "feed on the tender centers of Potentilla tenuiloba" (Comstock, 1927), and may use Potentilla (Horkelia) bolanderi in southern California (Emmel & Emmel, 1973). Lembert (1894) observed oviposition of ruralis in the center of Potentilla (Horkelia) fusca plants. Tietz (1972) lists Potentilla douglasii as a foodplant for ruralis, which is a synonym of P. (H.) fusca. Both Tietz (1972) and Garth (1935) list Sidalcea (Malvaceae) for ruralis but give no documentation. Sidalcea must be considered erroneous for ruralis, or based on misidentified animals, until proven otherwise. P. xanthus, like P. ruralis, seems to feed on Potentilla exclusively, and Malvaceae do not occur in most xanthus habitats. Female xanthus oviposited in the center of Potentilla sp. flowers near Flagstaff, Arizona (Kilian Roever, pers. comm.), are associated with P. ambigens (determined by William Weber, who doubts the status of ambigens as the

<-

Co., Colorado; 12-13, $ $, 14-15, 9 9, 16, 8, and 17, 9, nr. Cloudcroft, Otero Co., New Mexico; 18, $, Grandview Lookout, Coconino Co., Arizona; 19, $, and 20-21, 9 9, 5 mi. NW Flagstaff, Coconino Co., Arizona; 22, $, Lake Mary Road SE Flagstaff, Arizona; 23, $, Ditch Camp, 8000', Apache Co., Arizona; 24, 9, 16 mi. E. McNary, Apache Co., Arizona.

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Journal of the Lepidopterists' Society

Figs. 25-27. Male genitalia of Pyrgus spp. Lateral view (valvae and aedeagus removed), uncus and tegumen, posterior view and cross section of juxta (C is hole for aedeagus), medial view of right valva, and aedeagus. A and B are valval margins (A — harpe, B — cuiller) (cf. Table 1). Parts differ slightly in scale. 25, Bear Creek, Chaffee Co., Colorado; 26, Clear Creek, 10500', Clear Creek Co., Colorado; 27, nr. Game Ridge, Custer Co., Colorado.

type may have been an interspecific hybrid) near Cloudcroft, New Mexico, and are always associated with P. anserina in southern Colorado. Adult behavior. At high density, males search for females by flying just above the ground near the larval host, and few males occur in gully bottoms. At the usual low density, males mainly wait for females by perching in narrow dry gully bottoms. Courtship, in which male and female flutter about each other, occurs all day. Unreceptive females may fly upward about a meter repeatedly until the male departs. Adults occasionally feed on Taraxacum officinale and other flowers, and on manure and mud.

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Figs. 28-30. Female genitalia of Pyrgus spp. Ventral view, drawn opened on slides; left pre-papillar sclerite (tergum 8?) and left papilla analis omitted. Three drawings differ slightly in scale. 28, Marshall, Boulder Co., Colorado; 29, Copper, Siskiyou Co., California; 30, Howardsville, San Juan Co., Colorado.

Distribution. P. xanthus occurs in mountains from southern Colorado to southern New Mexico, northwest along the Mogollon Rim to near Flagstaff, Arizona. It probably occurs in southern Utah but has not yet been found northwest of the Colorado River (* = probable, specimens not examined.

COLORADO. 64 specimens examined. Douglas Co.: Russel Ridge, l-v-73, J. Scott; Park Co.: Beaver Creek near Fairplay, 10000', 20-vi-53, Hans Epstein*; near Fairplay, 10500', 30-v, F. M. Brown; Sacramento Creek near Alma, 10500', 31-V-53, F. M. Brown*; Antero Junction, vi-73, R. E. Stanford, M. Fisher; El Paso Co.: Beaver Creek, Rampart Range, 9000', 22-V-66, 4-vii-65, Samuel Johnson*; Chaffee Co.: near Trout Creek Pass, 19-vi-73, J. Scott; 5 miles W. of Buena Vista, 9000', 16-V-65, 8-vi-65, Samuel Johnson*; Poncha Pass, 9010', 27-V-72, J. Scott; Custer Co.:

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east of Game Ridge, 9400', 5-vi-71, Juanita Scott, 26-V-72, 18-vi-73, J. Scott; near Rosita, 8800', 26-V-72, J. Scott; Huerfano Co.: Devil's Hole, 9100', 15-16-vi-73, J. Scott; Saguache Co.: west of junction highway 114 and Luders Creek Road, 9200', 28-V-72, Glenn R. Scott; Luders Creek Camp, 10000', ll-vi-68, 8-vi-69, 30-V-71, Maurice Howard, 6-vi-71, Glenn and Juanita Scott, 23-vi-71, J. Scott; Saguache Park, 10500', 28-V-72, J. Scott; Costilla Co.: Culebra Mtn., v-44, Bernard Rotger*; Conejos Co.: Torsido Creek west of Capulin, 9700', 2-V-51, B. Rotger*; Mineral Co.: Wolf Creek Pass, vi, H. A. Freeman*; Gunnison Co.: Gothic, 9500', 20-vi-72, J. Scott; Tincup, 10200', 3-vii-65, M. Howard; Curecanti Creek, 8500', 21-vi-62, S. L. Ellis*; Montrose Co.: top of Black Mesa, 9700', -73, S. L. Ellis*; Cottonwood Creek, Uncompahgre Plateau, 8200', 4-vi-61, S. L. Ellis*; Dolores Co.: Dolores River near Lizard Head, 8500-9500', 29-V-39, F. M. Brown, J. W. Tilden*; Archuleta Co.: 7.7 mi. NE Pagosa Springs, 8-vi-69, S. L. Ellis; Hwy. 29 between Chromo and Chama, 2 mi. NW continental divide, 9-vi-69, S. L. Ellis; San Juan Co.: Howardsville, 3-vii-65, J. Scott.

NEW MEXICO. 127 specimens examined. Colfax Co.: Raton Mesa, 8800', 3-V-72, J. Scott; San Miguel Co.: near Rociada, 8000', 3-V-70, R. E. Stanford*; Bernalillo Co.: Sandia Mts., R. Holland*; Valencia Co.: Mt. Taylor, K. Roever*; Otero Co.: near Cloudcroft, Sacramento Mts., 8700', 21-iv-72, J. Scott; Pine Forest Camp, 8500', 6-V-61, 18-V-63, Kilian Roever; Catron Co.: Mogollon Range, 8-V-40, William Burdick.

ARIZONA. 20 specimens examined. Apache Co.: Highway 73, 16 mi. E. McNary, 30-V-70, K. Roever; Ditch Camp, North Fork White River, 8000', 30-V-71, K. Roever; Coconino Co.: Lake Mary Road, 7 mi. SE Flagstaff, 19-V-68, K. Roever; A-l Burn, Highway 180, 5 mi. NW Flagstaff, 31-V-64, 31-V-65, l-vi-63, K. Roever; Grandview Lookout, South Rim Grand Canyon, 20-iv-69, K. Roever; San Francisco Peaks, K. Roever*; Walnut Canyon, 23-iv-67, R. Funk*.

Literature Cited

Brown, F. M., D. Eff, & B. Rotger. 1957. Colorado Butterflies. Proc. Denver

Mus. Nat. Hist., Nos. 3-7. 368 p. Callaghan, C. J., & K. B. Tidwell. 1972. A checklist of Utah butterflies and

skippers. J. Res. Lepid. 10: 191-202. Comstock, J. A. 1927. Butterflies of California. Published by author. 397 p. Edwards, W. H. 1878. Descriptions of new species of North American Lepidop-

tera. Field & Forest 3: 142-143. Emmel, T. C, & J. F. Emmel. 1973. Butterflies of Southern California. Nat.

Hist. Mus. Los Angeles Co., Sci. Ser. 26. 148 p. Garth, J. S. 1935. Butterflies of Yosemite National Park. Bull. So. Calif. Acad.

Sci. 34: 37-75. Higgins, L. G., & N. D. Riley. 1970. A Field Guide to the Butterflies of Britain

and Europe. Collins, London. 380 p. Lembert, J. B. 1894. Food plants of some Californian Lepidoptera. Can. Ent.

26: 45-46. Tietz, H. M. 1972. An Index to the Described Life Histories, Early Stages, and

Hosts of the Macrolepidoptera of the Continental United States and Canada.

Allyn Museum of Entomology, Sarasota, Florida. 1041 p.