Erynnis lucilius

Description

The Columbine Duskywing (Erynnis lucilius) is a small, dark brown butterfly in the skipper family (Hesperiidae) with a wingspan of 21-29 mm. The upperside is a uniform, warm dark brown with an indistinct darker patch at the end of the forewing cell — the lack of a clearly defined dark patch is itself a useful identification feature, distinguishing it from some of its close relatives. The underside of the hindwing bears marginal and submarginal rows of well-defined pale spots that contrast with the darker ground colour. Males have a costal fold on the forewing containing yellow scent scales; females have a corresponding patch of scent scales on the seventh abdominal segment.

This species belongs to the "Persius complex" — a notoriously difficult group of three duskywing skippers that also includes the Wild Indigo Duskywing (E. baptisiae) and the Persius Duskywing (E. persius). The three species are extremely similar in appearance and were historically confused even by experienced lepidopterists. The most reliable way to distinguish them is by their larval host plants: Columbine Duskywing on Aquilegia, Wild Indigo Duskywing on Baptisia, and Persius Duskywing on a broader range of legumes. Where their ranges overlap — as they do in southern Ontario — careful observation of habitat and host plant association is essential for confident identification.

The species ranges from southern Quebec and Manitoba south through the northeastern United States to Virginia and Kentucky, with its Ontario populations concentrated in rocky, deciduous woodlands and ravines where wild columbine grows on limestone outcrops and well-drained slopes.

Lifecycle

Two broods are produced each year, with adults on the wing from April through September. Females deposit eggs singly on the underside of wild columbine leaves. The caterpillars feed on the foliage and construct individual shelters by tying leaves together with silk — a behaviour characteristic of the Pyrginae, the spread-winged skippers. They rest within these shelters between feeding bouts, emerging to consume the surrounding leaf tissue at night. Fully-grown caterpillars from the second brood enter hibernation in late autumn and overwinter within their leaf shelters on the ground. Pupation occurs the following spring, and the first adults of the new season emerge in April.

The specific host relationship with Aquilegia is among the tightest Lepidoptera-plant associations in the vault — the caterpillars feed almost exclusively on wild columbine (A. canadensis) and, where available, the naturalized garden columbine (A. vulgaris). This specialization makes the butterfly entirely dependent on the presence of its host plant, and populations cannot persist where columbine is absent.

Ecology

The Columbine Duskywing occupies a narrow ecological niche defined by the distribution of its host plant. In Ontario, it is most frequently encountered in rocky, deciduous and mixed woodlands on calcareous substrates — the same limestone outcrops, ravines, and wooded slopes where wild columbine thrives. The butterfly's habitat preference mirrors that of its host: well-drained, alkaline soils in partial shade, often on slopes or in gully systems where cool, moist microclimates moderate summer temperatures.

Adults nectar on a variety of spring and summer flowers, though specific nectar preferences are less well documented than for many other butterflies. Males perch on low vegetation in woodland openings and along trails to await passing females. The species is apparently secure across its range (G4 globally), though its restriction to a single host genus makes local populations vulnerable to the loss of columbine through habitat destruction, invasive species, or changes in forest composition. Conservation is not usually required, but monitoring of host plant populations serves as a proxy for butterfly population health.

Host Plants

Caterpillars feed exclusively on columbines in the genus Aquilegia. This is one of the most specific host plant relationships in the vault.

• Wild Columbine (Aquilegia canadensis) — primary native host
• Garden Columbine (Aquilegia vulgaris) — naturalized European species, occasionally used

Habitat

Occupies rocky, deciduous and mixed woodlands, particularly on limestone substrates, with a strong association with ravines, gullies, and wooded slopes. The species is most reliably found in proximity to populations of its host plant — a reliable search strategy for field identification. In Ontario, it occurs in the Carolinian and Great Lakes-St. Lawrence forest regions wherever suitable columbine habitat exists on calcareous soils. The species is not listed under the Species at Risk Act and is apparently secure across its range (NatureServe G4).