• May 29, 2025

Mottled Duskywing

Introduction 

The Mottled Duskywing (Erynnis martialis) is one of over 850 species of lepidatarians (butterflies and moths) occurring in Norfolk County and one of 5 species of duskywings (Erynnis sp.) in the Skipper Family (Hesperiidae). It is a small butterfly with a wingspan of 2.5-3.5 cm, completely brown on both the forewings and hindwings. These butterflies have a strong mottled pattern with various shades of brown, giving this species its name. The forewing sometimes has a purplish sheen in freshly emerged adults. Caterpillars are lime green with a dark head. The host plant for the caterpillar is New Jersey tea (Ceanothus americanus), in the buckthorn family (Rhamnaceae), and grows mostly in sunny areas within oak savannas. Mottled Duskywings are widely distributed occur across eastern North America, though it is not a common butterfly anywhere in its range.

Ecology 

In central Ontario (Northumberland County and Hastings County), only one generation of Mottled Duskywing Butterflies occurs per year. In southern areas, such as Norfolk County on the north shore of Lake Erie and Pinery Provincial Park on Lake Huron’s southeastern shore, Mottled Duskywing are able to produce two generations per year, likely owing to a warmer climate – one generation in May, the other in July. Mottled Duskywings breed in the spring during the months of May and June. The males perch to find females, and exhibit “puddling behaviour”, drinking from water puddles to obtain salts, minerals, and other critical nutrients which are scarce in their herbivorous diet. These are transferred to females during mating and help improve overall egg viability. Females then lay their eggs on New Jersey tea, which hatch a few days after they are laid. Adults live around 2-3 weeks in total. Caterpillars grow during a 2-month period. After larval development is completed in the autumn, these butterflies will overwinter as mature larvae. When warmer temperatures arrive, they will begin pupation, which will last 2 to 4 weeks.

Conservation Status 

Throughout eastern North America, Mottled Duskywings have experienced population declines. It is designated as Endangered in Ontario (COSSARO) and federally (COSEWIC). The species was recently reintroduced to Pinery Provincial Park and has known populations in Northumberland County and near Marmora in Hastings County.  The species was also reintroduced to Norfolk County in 2024. Threats to the Mottled Duskywing include habitat loss, including the conversion of native oak savanna to human uses (historically extensive), and the mesophication of oak savannas into woodlands and forests, caused by lack of ecological disturbance. Mesophication is a term used by ecologists to describe the transformation of a disturbance-adapted ecosystem into an ecosystem characterized by highly competitive, shade-tolerant species. It usually involves the densification of the shrub layer, and compositional shifts towards mesophytes – such as maples (Acer sp.), ashes (Fraxinus americana), and beeches (Fagus grandifolia). Increased shade levels and competition choke out the New Jersey tea plants that the Mottled Duskywing Butterfly relies on for its survival. Invasive species such as Garlic Mustard (Alliaria petiolata), Autumn Olive (Elaeagnus umbellata), and Quackgrass (Elymus repens) also are threats to native Oak savanna and are often actively removed by conservation organizations.

In Norfolk County, there have been extensive efforts to restore native oak savannas, coordinated by various organizations such as Long Point Basin Land Trust and Nature Conservancy of Canada – conservation organizations dedicated to protecting and restoring habitat. This work may increase potentially suitable habitat for Mottled Duskywings in the future.

Fun facts

  • Like other skippers, the Mottled Duskywing has a fast, erratic, “skipping” flight pattern, which can make it tricky to identify.
  • Mottled Duskywings thrive in dry habitats with sparse vegetation, such as open barrens and sandy patches in woodlands.
  • The larvae create shelters for themselves by weaving silk to tie leaves together. They spend a lot of their time inside these leaf-nests, likely for protection from predators and parasites.

 

Conservation Activities

May 29, 2025: Mottled Duskywing Butterfly Released at Stead Family Scientific Reserve

An endangered butterfly has been reintroduced to a Norfolk County nature reserve. Mottled Duskywings were released this week at Long Point Basin Land Trust’s (LPBLT’s) Stead Family Scientific Reserve.

The release is part of a multi-year, science-based recovery effort led by the Ontario Butterfly Species at Risk Recovery Team and supported by Environment and Climate Change Canada. This landmark initiative aims to return the Mottled Duskywing to its historical range in Norfolk County, where it disappeared in the late 1980s.

Klara Jones is leading the research and monitoring program, overseen by Jessica Linton of Natural Resource Solutions Incorporated. The Stead Family Scientific Reserve was selected as a release site in Norfolk County due to its oak savanna habitat and abundant New Jersey tea, the butterfly’s larval host plant.   In fact, the last sighting of a Mottled Duskywing was on this property in the late 1980s.

5 butterflies were release on Thursday with hundreds more planned for the site. Habitat restoration work by Long Point Basin Land Trust and regional conservation partners—including the St. Williams Conservation Reserve Community Council and the Nature Conservancy of Canada—has made the reintroduction possible. The site lies within the Long Point Walsingham Forest Priority Place, a nationally recognized biodiversity hotspot.

Acknowledgement of the project partners:

  • University of Guelph (Ryan Norris) is the lead researcher
  • Wildlife Preservation Canada leads the monitoring program (which employees Klara and Owen)
  • NRSI/Jessica Linton – Project Manager
  • Cambridge Butterfly Conservatory leads the captive rearing
  • Funding to date for the project has largely been through NSERC Alliance (U of G and NCC with contributions from other partners)
  • Western University (Nusha Keyghobadi) is leading the genetics

 

FAQs

Q: How long has the Mottled Duskywing conservation program been going on in Ontario?

“It’s been going on for around 15 years. Jessica Linton at Natural Resources Solutions Inc. has been the one who has been directing this whole project. It started out with sites at Marmora (Hasting’s County), Alderville (Northumberland County), and at Pinery Provincial Park, as well as Norfolk County. This year, in addition to three other sites in Norfolk, we have the Stead Property which has been scouted out for ideal habitat. We found ideal habitat, especially considering the presence of New Jersey tea, which is the host plant. Mottled Duskywings are funny species which only like their one host plant. This year, we decided to do releases to see how the habitat incorporates the butterfly. There are a few characteristics of the habitat – it needs to be open enough to support dense patches of its host plant. This property here is a good indicator that the butterflies may potentially be successful. For the next couple years, we will be releasing and monitoring, and finger-crossed – we’ll have some success here, reintroducing them back in Norfolk County”. Klara Jones

Q: Is this your first Mottled Duskywing release of this year in Norfolk County?

“This is our third butterfly release in Norfolk County, but our first release at this property. We have three other properties, and we have released 8 butterflies between two other properties. But hundreds of butterflies will be released in the future” Klara Jones

Q: How many people are part of your research team?

“In Norfolk County, the team consists of Owen and I, but of course we have director, who has been in charge of this project, and we have partners in this project as well – such as Guelph University, Norris Labs, Ontario Parks, Wildlife Preservation Canada, and of course, the Long Point Basin Land Trust, which is why we can do releases at this property. We don’t have a whole lot of research elsewhere this year. At the Pinery, we had good success, so we now can let the population do its thing” Klara Jones

Q: How are the caterpillars reared in the lab?

“The caterpillars are collected from our sites up in Marmora, so they will collect a few females and males, and once they lay eggs, researchers will keep close eye on them, so that way, when the eggs release the caterpillars, they will sort them into their matriline (lineage), and every day, they will do some tasks, like feed them and give them their host plant, and then the caterpillars will grow. Once it’s time for overwintering, they’ll put the caterpillars in a capsule that will monitor them, and it keeps the temperature at a consistent measurement, and that way, they bring them to us, and then we take care of the butterflies until they are ready for release” Klara Jones

Q: Where are the other release sites located?

“The other release sites are located around Backus Woods, and St. Williams Conservation Reserve” Klara Jones

Q: How many generations of the butterfly live each year?

“There are two generations of the butterfly living in Norfolk and the Pinery, but then the further north you get, such as Marmora and Alderville, there is only one generation, which is interesting! We assume that these differences are due to weather and climatic conditions – it is warmer earlier down south, and later (in the autumn), so they have a little bit of a headstart to their reproduction in Norfolk, and they can end a little later as well. Whereas up north, they get started a little later. And their host plant is not as long in flower” Klara Jones

Q: What role does Long Point Basin Land Trust play in conservation?

Long Point Basin Land Trust works locally with a community of partners to conserve the rich biodiversity and habitats found here.  This area hosts an incredible variety of plants and animals, some of which are increasingly rare and only found in small pockets of habitat across the landscape. The land trust acquires and cares for significant habitats and invites the public to enjoy these lands through managed trails and educational and volunteer events. Some of the best remaining natural habitats in southwestern Ontario are found in the Long Point Basin and conserving these gems is a major focus of the land trust. Wendy Cridland, Executive Director

 

In the Media

 

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Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University

All photos provided by Matthew Palarchio & LPBLT Staff

 

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