years. Here we report on the response of that regal fritillary population to a spring burn and comment on the population's persistence under a 20-year burn regime. These data are part of a larger study but are reported here because they provide timely information for the debate on use of fire for invertebrate management in prairies. Nine-mile Prairie is a 97-ha native tallgrass diverse biotic group of the tallgrass prairie prairie approximately 14.5 km northwest Response of Regal ecosystem (Opler 1981, Panzer 1988, of Lincoln, Lancaster County, Nebraska, Arenz and Joern 1996). Among inverte- Fritillary (Speyeria USA (40° 52' N, 96° 49' W). The prairie brates, lepidopterans have received partic- has been owned by the University of Ne- idalia Drury) to Spring ular attention (Opler 1981, Panzer 1988, braska Foundation since 1984, but has been Moffat and McPhillips 1993). As aware- Burning in an Eastern studied by university personnel since the ness of the importance of invertebrate pop- early 1900s (Kaul and Rolfsmeier 1987). Nebraska Tallgrass ulations in tallgrass prairie has increased, Three hundred ninety-two vascular plant Prairie, USA so has concern regarding the use of fire as species have been found on the prairie a management tool—especially the effect (Kaul and Rolfsmeier 1987). Over the past of extent, frequency, and timing of Jeffrey J. Huebschman' century, Nine-mile Prairie was pre-scribed burns on invertebrate Thomas B. Bragg occasion-ally hayed and lightly grazed, populations (e.g., Moffat and McPhillips but since a change in ownership in 1979, Department of Biology University 1993). In general, the response of the prairie has been mostly managed with of Nebraska at Omaha Omaha, invertebrates to fire management differs springtime burning on a 3- to 4-year Nebraska 68182-0040 USA by species, and by fire extent, frequency, fire-return interval (Kaul and Rolfsmeier and timing (re-viewed by Reed 1997). 1987). Over half of the prairie was burned Fire has been a major force in the forma- on 15 May 1995, and the portion not tion and maintenance of the tallgrass prai- The regal fritillary butterfly (Speyeria ida- burned in 1995 was burned on 23 May rie ecosystem in North America (Collins lia Drury) is considered a key indicator 1997. No burns were conducted in 1996. 1990, Bragg 1995, Steinauer and Collins species of native tallgrass prairie (Ham- Prescribed fires after the first week in 1996); thus, the role of fire and its effects mond and McCorkle 1983), and has been May are considered late in the spring on tallgrass prairie plant communities have classified as both a remnant-dependent burning season (T.B. Bragg, pers. obs.) been well studied (e.g., Daubenmire 1968, species (Panzer et al. 1995) and a prairie and may have severe effects on Vogl 1974, Collins and Gibson 1990, Sve- specialist (Swengel 1996). Because invertebrates (see Bragg 1995) because jcar 1990). It is generally accepted that de-clines in abundance have been noted most insects have emerged by that time prescribed fire, when applied at the appro- throughout the species' range (Opler 1981, and are in, on, or above the litter that is the priate season and frequency, plays an im- 1992; Bliss and Schweitzer 1987), specific fuel for burning. portant role in tallgrass prairie manage- information about the effects of prairie ment by promoting long-term species management on the regal fritillary is valu- In 1996 we established a single 4460-m diversity in the plant community (Bragg able. Swengel (1996) reported a negative butterfly-survey transect that traversed all 1991). Furthermore, lack of fire manage- response to fire by regal fritillary and major regions of Nine-mile Prairie. Fol- ment on prairie remnants may cause her- concluded that habitat maintenance by lowing established procedures (Thomas baceous plant species losses by facilitat- haying is more favorable than burning 1983, Gall 1985, P. Hammond; Oregon ing woody plant encroachment (Bragg and where this species is concerned. However, State University, Corvallis, pers. cont.), Hulbert 1976) and also by minimizing the Swengel's (1996) conclusions have been surveys consisted of walking the preestab- dynamic conditions necessary for persis- questioned (Schwartz 1998). Schwartz lished transect at a steady pace and count- tance of certain plant species (Leach and (1998) con-tended that the issue is not ing each regal fritillary butterfly seen within Givnish 1996). whether prairie butterflies, or other an area 5 m in front and 5 m to either side species, are temporarily reduced by fire of the survey transect. All surveys were Prairie management strategies have his- management, but rather whether fire conducted by a single observer to limit torically focused on the plant community, management alters the ability of variablity. Surveys were first conducted in but recent attention has been given to an- populations to persist in a given habitat? 1996, when the prairie had not been burned, imals, particularly invertebrates, the most We observed the effects of a prescribed and again in 1997, when approximately spring burn on a regal fritillary population one-third of the prairie was burned. Data in an eastern Nebraska tallgrass prairie Corresponding author e-mail: collected included whether butterfly ob- jhuebscl @bigred.unl.edu that has been managed since 1979 with servations occurred in burned or unburned spring burns applied every three to four 386 Natural Areas Journal Volume 20 (4), 2000 Figure 1. Regal fritillary butterfly counts before (1996) and after burning (1997) by week. areas. Surveys for regal fritillary were individuals counted on the burned portion Nine-mile Prairie: regal fritillary con-ducted approximately weekly for a total and 61 counted on the unburned portion. butter-flies were observed throughout the of eight weeks beginning after butterflies After week four, however, the two popula- prairie in 1996, when approximately half of were first observed in the region. In 1996 tions were similar in size and remained so the prairie was burned in mid-May in 1995. the first and last survey dates were 19 June for the rest of the surveying period, sug- and 12 August; in 1997 they were 21 June gesting dispersal of regal fritillary from the The regal fritillary population at Nine-mile and 20 August. unburned portion of the prairie to the burned Prairie reflects the net effect of past man- area. agement, which has included spring burn- Surveys were generally conducted from ing since 1979. The persistence of regal 1000 to 1530 h on sunny (less than 50% The short-term response of regal fritillary to fritillary at this site suggests that burning at cloud cover) days, with temperatures above prescribed fire at Nine-mile Prairie was not a 3- to 4-year frequency, while leaving 21° C. However, when temperatures ex- surprising. Larvae almost certainly suffered adjacent areas unburned, is a realistic ceeded 27° C, surveys were conducted with a direct mortality in the burned portion of the long-term management plan for this species cloud cover of up to 75%, or surveying time prairie in 1997 because they were at Nine-mile Prairie and, presumably, at was extended (0930–1600 h), providing that presumably above ground feeding on similar prairie sites in eastern Nebraska. cloud cover remained less than 50%. violets (Viola L. spp.), their larval host Successful dispersal of regal fritillary Surveying criteria were based on Gall plants (Opler and Krizek 1984, Bliss and through-out the prairie, following prairie (1985). Schweitzer 1987, Opler 1992) at the time regrowth and recovery from burn treatment, of the fire in mid-May. Violets are is probably a key factor contributing to the Regal fritillary butterflies were observed avail-able to regal fritillary larvae on long-term persistence of this species at throughout Nine-mile Prairie in 1996. Nine-mile Prairie throughout May Nine-mile Prairie under the current fire Late-spring burning in 1997, however, had (Huebschman 1998). Subsequent dispersal management regime. a noticeable impact on regal fritillary distri- of adult regal fritillary from the unburned bution and abundance. No butterflies were prairie to burned areas is also not surprising detected in the burned portion of the prairie because these butterflies are strong Acknowlegments in 1997 during the first two weeks of dispersers (Bliss and Schweitzer 1987), and, We thank the Nine-mile Prairie Commit-tee surveys, in contrast to the 21 counted in the when dispersal occured by mid-July, the members for approved use of Nine-mile unburned portion during that time (Figure burned prairie was lush with vegetative Prairie as a research site. This study 1). By the third survey week, the difference regrowth (J.J. Huebschman, pers. ohs.). received financial support from the De- between the burned and unburned areas was Successful dispersal and recolonization of partment of Biology, University of Ne- the greatest for the year with 4 regal fritillary following a burn presumably braska at Omaha, and the Center for Great occurs at Volume 20 (4), 2000 Natural Areas Journal 387 Plains Studies. We thank Steve Spomer and Dr. Bragg, T.B. and L.C. Hulbert. 1976. Woody Opler, P.A. 1992. A Field Guide to Eastern Leon Higley, both in the Department of plant invasion of unburned Kansas bluestem Butterflies. Houghton Mifflin Company, Entomology, University of Nebraska—Lincoln, prairie. Journal of Range Management New York. 396 pp. and the Natural Areas Journal Editorial Board 29:19-24. Opler, P.A. and G.O. Krizek. 1984. Butterflies for critical review of an earlier draft of the Collins, S.L. 1990. lntroducl:ion: fire as a nat- East of the Great Plains: An Illustrated manuscript. ural disturbance in tallgrass prairie ecosys- Natural History. The John Hopkins Univer- tems. Pp. 3-7 in S.L.