Saving rare butterflies, one plant survey at a time

By Chris Ludwig, former Chief Biologist for the state of Virginia

On June 10, 1993, as botanist for the Virginia Natural Heritage Program, I set out to look for rare plants in Halifax County, Virginia. My quest was to relocate two plant species that had never been found elsewhere in the Commonwealth: Carolina Thistle (Cirsium carolinianum) and Wild Ipecac (Gillenia stipulata). They had been collected in the County 20 years prior by two intrepid Virginia botanists, Charles ‘Mo’ Stevens and Alton Harvill. My explorations took me to Allen’s Mill Road and a grassy hardwood/shortleaf pine woodland that a timber company was converting to rows of loblolly pine plantation. The plants I sought were abundant along the road and on a transmission line right-of-way, and I knew we were into something special.

Difficult Creek, Virginia’s 39th Natural Area Preserve

Flash forward to 2008: 818 acres have been acquired by the Virginia Department of Conservation and Recreation, and the site is dedicated as the Difficult Creek Natural Area Preserve. As the state’s 39th Virginia Natural Area Preserve, it has been forever set aside to be protected and managed for its biodiversity values. At this point, we had found most of the site’s 16 rare plant species and fire management was bringing back a healthier, more vibrant, understory plant community.

On May 17, 2008, Anne Chazal, field zoologist for Virginia Natural Heritage, collected insects on the preserve as part of a general biodiversity inventory conducted on many of the Preserves. She would swing her net between prescribed-fire units 2 and 3, and capture a butterfly which she would later pin and submit to other staff for identification. Not long after an identification came back: Mottled Duskywing (Erynnis martialis)!

 
Female Mottled Duskywing ( Erynnis martialis ). Imaged May 15, 2018. Nectaring on Violet Wood Sorrel,  Oxalis violacea

Female Mottled Duskywing (Erynnis martialis). Imaged May 15, 2018. Nectaring on Violet Wood Sorrel, Oxalis violacea

 

When deer compete with butterflies for food plants

Throughout the eastern U.S., this small butterfly, a skipper in the genus Erynnis, has virtually disappeared. The explanation for this is up for some debate. First, the butterfly is 100% dependent on the shrub known as New Jersey Tea (Ceanothus americanus), and this is a particularly coveted food source for White-tailed Deer, an ungulate whose density in the eastern U.S. is staggering. Many conjecture that deer have impacted the New Jersey Tea population to the point that the Duskywing is being wiped out.

Another explanation, less obvious, but to me just as, if not more, plausible is the loss of grasslands. While New Jersey Tea barely holds on in forested settings, it thrives in open, grassy habitats. Where can Mottled Duskywing still be found? Only where some of the finest grasslands remain in the east. For example, it is found in the Albany Pine Bush of New York, a famous remnant grassland site protected and carefully managed for its grassland communities and rare butterflies. Numerous other grassland preserves tell the same story – protect and restore the grassland habitat and the butterfly can survive.

Even one rare plant survey can make a huge difference

Consider what would have happened had I not come across this site. Industrial southern pine timber management would have continued and the remaining woodlands with their grassy understory would have been lost. The roadside and utility rights-of-way with their grassland habitat would have slowly succumbed to herbicide and ill-timed mechanical vegetation management. No more grassland, no more New Jersey Tea, and no more butterfly.

In short it is important to remember that our rare and declining insects like the Mottled Duskywing, along with our rare plants, need our remaining grasslands to make their last stand before they are lost forever. And remember – it’s a tangled web: plants feed the insects, insects feed the birds, insects pollinate the plants, and on and on it goes. 

A diverse and vibrant fauna means a diverse and vibrant grassland!

Hardwood/shortleaf pine savanna at Difficult Creek Natural Area Preserve imaged June 3, 2019. Note the thriving grassy understory. New Jersey tea is scattered throughout this area and Mottled Duskywings are consistently found over a large are of this Natural Area Preserve.

Hardwood/shortleaf pine savanna at Difficult Creek Natural Area Preserve imaged June 3, 2019. Note the thriving grassy understory. New Jersey tea is scattered throughout this area and Mottled Duskywings are consistently found over a large are of this Natural Area Preserve.