1994 Proceedings
North American Conference on Savannas and Barrens

The oak-shagbark hickory savannah or "barrens" of Lake Argyle State Park and oak-hickory and oak-red cedar savannah of other parts of western and southern McDonough County lie within the Lamoine River drainage. The area is characterized by quick transitions into adjacent habits of upland acid-soil tallgrass prairie openings; mesic and damp ravines; mature oak-hickory forest; and river riparian forest. Of greatest immediate interest are the relationships of the "barrens" (also called hollows) butterfly fauna to the prairie and ravine habitat fauna. Each environment is characterized by particular index species, but local and transitory transgression of index species into other adjacent habitats does occur.

The "barrens" or savannah habitat was first recognized by Mead (1846) as distinct from tallgrass prairie habitat and from forest ("timbers") during his botanical investigations. The uniqueness of the "barrens" habitat has been further substantiated by Packard (see Breining 1993), our studies and others. This habitat in west central Illinois is underlain by acid soil members of the Clinton-Hickory-Keomah group which are developed on siliceous till of Illinoisan (Quaternary) age and on pyritiferous sandstone, shale, coal and gypsiferous limestone of Pennsylvanian age.

STUDY AREA

Two study areas are described. The first is the southern half of Lake Argyle State Park, located approximately 2.4-3.0 kilometers north of Colchester, McDonough County, Illinois. The second is the Warnock Farm Site, approximately 4.5 kilometers south of Fandon, McDonough County (Fandon 7 1/2 minute quadrangle, T4N, R3W, sections 16 and 17).

Oak-hickory barrens, interspersed with small openings of bluestem prairie grasses are typical at Lake Argyle State Park. Oak-hickory and oak-red cedar barrens occur locally on Pennsylvanian-age sandstone at the Warnock Farm Site, but always in the vicinity of virgin and semi-virgin tall bluestem grass prairie.

METHODS OF STUDY AND OBSERVATIONS

The data presented here are the result of extensive field studies during 1975-1985 on butterfly faunas of the region (Sedman and Hess 1985) and additional observations previous to, and subsequent to that. Index species were discovered for each habitat discussed in this paper.

RESULTS AND DISCUSSION

Barrens

Barrens (oak-hickory savannah) typically contain the hesperid (skipper) species, Erynnis brizo (Boisduval and LeConte) and Erynnis horatius (Scudder and Burgess). The former flies in April-May, visiting low flowers such as Viola pedata (Table 1). Rafinesque whereas the latter flies in June to August, feeding on higher flowers. Both are larval Quercus feeders, preferring juvenile shoots.

Lycaenids of the barrens include the hairstreaks, Satyrium edwardsii (Saunders) and Satyrium caryaevorus (McDonough), closely associated with Quercus and Carya. Males of both species are strongly territorial and both sexes feed on tall flowers such as Meliotis and Asclepias. Larval association with ant species found on southwestern Michigan oak barrens near Quercus velutina and Quercus coccinea has been documented (Webster and Nielsen 1984) for Satyrium edwardsii and is suspected in our area, but not proved. Both species fly in June-July in McDonough County and Satyrium edwardsii is also known in the Quercus velutina-Quercus marilandica barrens of Sand Ridge State Forest, Mason County, Illinois. At the Warnock Farm Site, Callophrys gryneus (Hubner) is associated with oak-red cedar barrens in April-May and again in June-July. Males are strongly territorial at the tops of Juniperus virginiana, the larval foodplant. Adults feed on a variety of flowers such as Gnaphalium and Meliotis.

Nymphalids include Anaea andria Scudder in strongly migratory years and a possibly distinct and as yet undescribed Phyciodes species differing from Phyciodes tharos (Drury) in its more extensive orange markings; higher flight; wariness; and timing of broods. This Phyciodes is also known from the barrens and prairies of Sand Ridge State Forest.

Prairies

Upland acid-soil prairies characterized by bunchgrasses, especially big and little bluestems, form openings adjacent to barrens and contain their own suite of butterfly species.

Hesperids include Problema byssus (Edwards), Atrytone logan (Edwards), Hesperia leonardus Harris, Thorybes bathyllus (Smith) and Erynnis baptisiae (Forbes). Most of these are bluestem grass or legume larval feeders (Table 2)

Problema byssus appears in late June-July and the larva is a big bluestem feeder. Male and female adults frequently visit Gnaphalium and coneflowers. Females tend to be communal whereas males are highly territorial around the tops of Andropogon gerardii bracts. Atrytone logan is not restricted to prairies but is especially abundant there. Larvae feed chiefly on Andropogon gerardii in our area.

Thorybes bathyllus is local, often occurring around Lespedeza (bush clovers) which may serve as the larval host. The closely related and broader ranging Thorybes pylades prefers tick trefoils in our region.

Hesperia leonardus flies only in the last week of August and during September. The larval grass host is not known, but adults of the colony strongly depend on Liatris as an adult nectar source along a roadside in Lake Argyle State Park. Some decrease in numbers in recent years may be due to planted pines which are usurping some of the prairie environment locally.

Erynnis baptisiae is a larval and adult feeder on Baptisia leucantha. It appears throughout spring and summer in at least three broods.

Other prairie butterfly species include the nymphalids Chlosyne gorgone carlota Reakirt and Chlosyne nycteis (Doubleday); and the migrant breeder sulfur, Eurema lisa (Boisduval and Le Conte), dependent on Cassia fasciculata as a larval host, very abundant on our prairies. The satyrid, Cercyonis pegala olympus is also found on the bunchgrass prairies.

Ravines and North-Facing Slopes

Mesic to damp ravines and forested, north-facing slopes are the haunt of Celastrina ebenina Clench, a lycaenid typical of Appalachian and Ozark forests (see Clench 1972). Its biology has been studied by Wagner and Mellichamp (1978). Larvae feed on Aruncus dioicus (goat's beard), a rosaceous shrub limited to ravines and north-facing slopes (Table 3). The plant is common in Lake Argyle State Park and larvae were observed on it, May 30, 1984. Adult females feed on Geranium and courtship flights have been observed among Arunus dioicus and Rubus allegheniensis on slopes nearby. The species flies only in late April and early May in our area and the park is the farthest north location thus far known for this butterfly.

Transgression of Index Species into Other Habitats

Eurema lisa, Erynnis baptisiae and Cercyonis pegala olympus have been observed to stray from prairie habitat into "barrens" habitat on numerous occasions. Conversely, Satyrium edwardsii and Satyrium caryaevorus wander from "barrens" into prairie openings to seek nectar sources.

A male Celastrina ebenina was observed once (May 15, 1979) in the process of flying from one ravine to a neighboring one over upland acid-soil prairie. Females are very restricted to shaded slopes and have not been observed to fly beyond woodland edges in our area.

CONCLUSIONS

Studies indicate that rapid changes from "barrens" habitat to upland acid-soil prairie to mesic and damp ravine environment occur in McDonough County, Illinois. Each habitat has a characteristic suite of index butterfly species which transgress the other discussed habitats only occasionally.

ACKNOWLEDGMENTS

Appreciation is expressed to Dr. John Warnock, Professor Emeritus, Department of Biological Sciences, Western Illinois University and to Mr. Wayne White, past ranger of Lake Argyle State Park for their assistance. We also thank Dr. Robert Henry for further information on Dr. Samuel B. Mead and express our appreciation to Linda C. Hess for help typing and in editing.

LITERATURE CITED

Breining, G. 1993. The case of the missing ecosystem. Nature Conservancy, Nov.-Dec.: 11-15.

Clench, H. K. 1972. Celastrina ebenina, a new species of Lycaenidae from the eastern United States. Carnegie Museum Annuals 44: 33-44.

Mead, S. B. 1846. Catalogue of plants growing spontaneously in the state of Illinois, the principal part near Augusta, Hancock County. The Prairie Farmer 6: 35-36, 60, 93, 119-122.

Sedman, Y. and Hess, D. F. 1985. The Butterflies of West Central Illinois. Western Illinois University Series in the Biological Sciences 11: 120 p.

Wagner, H., Jr. and Mellichamp, T. 1978. Foodplant, habitat and range of Celastrina ebenina (Lycaenidae). Journal of the Lepidopterists' Society 32, no. 1:20-36.

Webster, R. P. and Nielsen, M. C. 1984. Myrmecophily in the Edward's Hairstreak Butterfly Satyrium edwardsii (Lycaenidae). Journal of the Lepidopterists' Society 38:121-133.

Table 1. Notes on adult and larval food plants for index butterfly fauna found in barrens.

Table 2. Notes on adult and larval food plants for index butterfly fauna found in prairie habitats.

Table 3. Notes on adult and larval food plants for index butterfly fauna found in moist ravines and north slopes