Systematics: Described originally as Lacerta 6-lineata (= sex- lineata) by Carolus Linnaeus in 1766, based on a specimen sent to him by Alexander Garden from "Carolina." Schmidt (1953) restricted the type locality to Charleston, South Carolina. Dumeril and Bibron (1839) first used the genus Cnemidophorus for this lizard. Hoffman (1957a) described A. sexlineatus oligoporus based on specimens he collected from Alleghany County, Virginia, and elsewhere, but had to change the name to A. s. pauciporus (Hoffman, 1957b) because oligoporus was already in use. Duellman and Zweifel (1962) discovered that the variation described by Hoffman for the new subspecies was found in other parts of the range and relegated the name to junior synonym status. Taxonomy for Aspidoscelis follows Maslin and Secoy (1986, Contrib. Zool. Univ. Colorado Mus. 1: 1–60) and Wright (1993, in J. W. Wright and L. J. Vitt [eds.], Biology of Whiptail Lizards [Genus Cnemidophorus], Oklahoma Mus. Nat. Hist., Pp. 27–81).

Description: A moderate-sized lizard with a pointed snout reaching a maximum snout-vent length (SVL) of 75 mm (3.0 inches) and a total length of 241 mm (9.5 inches) (Conant and Collins, 1991). In Virginia, maximum known SVL is 76 mm (3.0 inches) and maximum total length is 247 mm (9.7 inches). Tail length in the Virginia sample was 63.3-78.6% (ave. = 68.4 ± 2.3, n = 82) of total length.

Scutellation: Dorsal scales granular, not shiny, and nonoverlapping; ventral scales (= plates) rectangular and in 8 longitudinal rows; ventral plates in mid ventral row 29-36 (ave. = 32.7 ± 1.4, n = 105); granular scales around midbody (not counting ventral plates) 82-103 (ave. = 93.1 ± 3.9, n = 106); supralabials 7/7 (35.8%, n = 109), 7/8 (31.2%), 8/8 (25.7%), or combinations of 6-9 (7.3%); supranasals absent; rostral separated from frontonasal by paired nasal scales; mental single; postmental 1; femoral pores 23-34 (ave. = 29.7 ± 2.0, n = 108); number of lamellae on right 4th toe 20-31 (ave. = 26.7 ± 2.0, n = 109); scales on tail rectangular, not granular.

Coloration and Pattern: Dorsum with 6 cream, white, yellow, or bluish, narrow longitudinal stripes on a dark-brown body; origin of all light stripes behind eyes; a light-brown to tan stripe runs from head to base of tail; scales between dorsolateral stripes 6-13 (ave. = 9.3 ± 1.5, n = 109); dorsolateral stripes terminate at base of tail but 2 lateral stripes extend onto tail to about one-third its length; tail brown dorsally, dark brown laterally with 2 light stripes, and cream to bluish ventrally; dorsum of head light brown to tan; venter cream to bluish.

Sexual Dimorphism: Adult males (SVL 52-72 mm, ave. = 64.9 ± 5.5, n = 49) were slightly smaller than adult females (SVL 52-76 mm, ave. = 66.8 ± 6.5, n = 61) in body size. Sexual dimorphism index was 0.03. Complete tail length relative to total length was slightly higher in males (63.3- 78.6%, ave. = 69.3 ± 2.7, n = 33) than in females (63.8-72.1%, 67.8 ± 1.8, n = 37). The number of granules around the midbody averaged slightly higher in males (82-103, ave. = 94.2 ± 4.1, n = 45) than in females (83-99, ave. = 92.3 ± 3.7, n = 60). Counts of femoral pores (males 23-33, ave. = 28.9 ± 2.0, n = 48; females 24-34, ave. = 29.6 ± 2.0, n = 59), lamellae on the right 4th toe (males 23-31, ave. = 27.0 ± 1.9, n = 48; females 20-30, ave. = 26.5 ± 2.0, n = 60), number of divided parietal scales (males 2-7, ave. = 4.3 ± 1.1, n = 47; females 2-6, ave. = 4.0 ± 1.1, n = 59), width of dorsal stripe (males 6-13, ave. = 9.3 ± 1.7, n = 48; females 6-12, ave. = 9.3 ± 1.3. n = 60V and ventral scales (males 30-36, ave. = 32.7 ± 1.4, n = 46; females 29-36, ave. = 32.6 ± 1.6, n = 58) were not sexually dimorphic. The venter of males is usually bluish, whereas that of females is usually whitish.

Juveniles: Color and pattern of juveniles are similar to adults except that the tail is bluish and the venter is usually cream in color. The bluish tail color fades into brown or gray with age. Average size at hatching in North Carolina A. sexlineatus populations was 32.5 mm SVL, total length was 93.5 mm, and body mass was 0.84 g (E. Brown, 1956). Size at hatching in Virginia is unknown.

Confusing Species: The only other lizards with legs that have stripes are the skinks in the genus Plestiodon. These lizards have 5 stripes (except as old males) and broad, shiny, overlapping scales.

Geographic Variation:Substantial geographic variation exists among Virginia populations of A. sexlineatus in several scale characters. The average number of granules around the midbody in the southeastern Coastal Plain (93.7 ± 2.7, n = 56) and the northern Piedmont (93.4 ± 4.6, n = 39) was higher than that in the southern Piedmont (88.4 ± 3.9, n 10). There was a slight decrease in number of ventral scales from an average of 33.2 ± 1.4 (n = 55) in the southeast to an average of 31.9 ± 1.3 (n = 39) in the northern Piedmont. The number of granules between the paravertebral light stripes was higher in the southeastern Coastal Plain (ave. = 10.3 ± 1.0, n = 56) than in the Piedmont (ave. = 8.1 ± 1.0, n = 52). The number of lamellae on the right 4th toe varied from an average high of 27.8 ±1.5 (n = 56) in the southeast to a low of 25.5 ± 1.9 42) in the northern Piedmont.

The number of divided parietal (head) scales was shown by Hoffman (1949a) to vary from 3 to 11 in Virginia samples. This and the number of femoral pores were the primary characters he used to separate the now-synonymized A. s. panciporus from the nominate subspecies (Hoffman, 1957a, 1957b). The number of divided parietals was higher in the southeastern Coastal Plain (ave. = 4.3 ± 1.0 ,n = 56) than in the southern Piedmont (ave. = 3.2 ± 0.8, n = 10) and the northern Piedmont (ave. = 3.9 ± 1.1, n = 40). The number of femoral pores, however, was similar among Virginia samples (SE Coastal Plain ave. = 30.0 ± 1.9, n = 55; S Piedmont ave. = 30.0 ± 2.0, n = 10; N Piedmont ave. = 29.2 ± 2.0, n = 42).

Biology: Aspidoscelis sexlineatus inhabits hot, open, xeric areas in fields, open woods, dunes in coastal barrier ecosystems, and agricultural and urban areas. They have been found on open road embankments in the Piedmont and along railroad cuts in the Shenandoah Valley. Unconfirmed habitats in Virginia are shale barrens. Racerunners are particularly abundant in dry, sandy areas of the Coastal Plain. They will utilize grass clumps and overhanging vegetation, such as wax myrtle trees (Myrica cerifera), for cover and shade. The type of vegetation is not as important as its structure. Overwintering in Alabama and Georgia, and presumably Virginia, occurs in burrows constructed in well-drained, sun-exposed, sandy soil and lasts 8-9 months (Etheridge et al., 1983). Males in these areas emerged in late April, whereas females emerged in early May (Etheridge et al., 1986). Juveniles usually emerge earlier and remain active longer than adults. Capture dates of Virginia Eastern Six-lined Racerunners were 30 April (adult) through 16 September (juvenile). This lizard maintains the highest body temperature of any Virginia reptile. Recorded temperatures of active racerunners were 38.0-42.0°C (ave. = 40.5 ± 1.1, n = 16) when ambient temperatures were 26.6-27.5°C (ave. = 27.1 ± 0.5, n = 15). Apparently, the need to maintain these high temperatures restricts their activity season to the warmest months.

Like other Virginia lizards, Eastern Six-lined Racerunners consume a wide variety of invertebrates. Termites usually form the basis of cnemidophorine diets. They and other hidden prey are found by actively foraging in and under vegetation cover. The prey of Virginia racerunners has not been studied, but McCauley (1939) listed the following prey types in a Maryland sample: grasshoppers, ants, lepidopteran larvae and adults, true bugs, beetle adults and larvae, and spiders. Predators of Eastern Six-lined Racerunners have not been identified in Virginia, but Brown (1979) found a specimen in the stomach of a Northern Black Racers (Coluber constrictor) in North Carolina. Most predation events probably occur in burrows when the lizards are inactive. Their utilization of speed as an escape method may be effective against avian predation. Speed will not, however, deter the introduced fire ant (Solenopsis invicta) from attacking and eating A. sexlineatus eggs in nests, as has been demonstrated in Alabama (Mount, 1981; Mount et al., 1981).

Female Eastern Six-lined Racerunner are oviparous and lay one to two clutches per year (Martof et al., 1980; Trauth, 1983). Mating occurs in May and early June in the Midwest (Fitch, 1958); no dates are available for Virginia populations. Males follow female trails and forcibly mate with them, even digging them out of burrows to do so (Carpenter, 1977). The smallest mature female with developing follicles was 52 mm SVL and the smallest mature male with an enlarged testis was 51 mm SVL. In North Carolina and other southern states, nesting occurs in shallow burrows constructed by females in loose sandy soil and sawdust piles during late May and June (E. Brown, 1956; Trauth, 1983). Females from Virginia containing oviductal eggs were found between 26 May and 12 June. Clutch size based on enlarged follicles and oviductal eggs was 1-5 (ave. = 2.8 ± 0.8, n = 26). Elmer Brown (1956) discovered 1-5 eggs in nests in the North Carolina Piedmont, and Trauth (1983) noted a maximum clutch size of 8. Females do not brood their eggs, and communal nests are unknown. Average egg size and mass at oviposition in North Carolina was 16.3 x 9.3 mm and 0.78 g, respectively, and hatching occurred between 27 June and 5 September after an incubation period of about 60 days (E. Brown, 1956). Egg measurements and hatching dates are unknown for Virginia populations.

In South Carolina, A. sexlineatus density was 2.5 lizards per 100 m² and growth rates were 0.058 mm per day for females and 0.045 mm per day for males (Beilis, 1964). In his study of a Kansas population, Fitch (1958) calculated a density of 140 race-runners per hectare, an annual survivorship rate of 41%, and a maximum life span of 6 years. Eastern Six-lined Racerunners are very active lizards. Escape from predators and observers is accomplished by sprinting under vegetation and into burrows. Eastern Six-lined Racerunners are not territorial. In studies on Oklahoma racerunners of the western subspecies, males and some females were found to displace, chase, and bite members of the same sex in the formation and maintenance of a loose, linear dominance hierarchy (Carpenter, 1960; Leuck, 1985). It is not known if the eastern subspecies, found in Virginia, is as aggressive as the western subspecies.

Eastern Six-lined Racerunners do not autotomize their tails like skinks and glass lizards. The tails of some Virginia specimens were incomplete, but the majority were complete, unlike the samples of skinks. The tail is used to assist in balance during running and not, at least in adults, to distract predators.

Remarks: Other common names in Virginia are sandlapper (Dunn, 1918, 1936); six-lined lizard, sand-lapper, and race runner (Carroll, 1950); and six-lined skink.

The oldest specimen of this species from Virginia in existence (MCZ 570) was collected during the Seven Days' Battle near Richmond in 1862 by General George G. Meade, commander of the Union forces, or one of his staff, and sent to Louis Agassiz at Harvard University as a gift in order to secure the address of a naturalist, Theodore Lyman, who Meade wanted on his staff. This historical connection is explored in Tobey (1991).

Conservation and Management: This lizard is not currently a species of special concern in Virginia. It is one of the reptiles that has benefited from man's alteration of the landscape, and populations located on roadcut banks and along railroad tracks attest to its success in nonnatural habitats. However, maintaining this species as an element of Virginia's biodiversity in natural habitats necessitates a better assessment than we now have of the distribution of this lizard in such sites. Management of local populations requires the maintenance of large open areas on well-drained soils, but old field succession will eliminate the microhabitat necessary for construction of burrows for overwintering and nesting. Another threat is the introduced fire ant, which is particularly successful in the habitats favored by A. sexlineatus. All outbreaks of this harmful pest need to be eradicated, as local population extinctions of Eastern Six-lined Racerunners are possible if they are not.

U.S. Range