European Skipper (Thymelicus lineola) in Northwest, BC

Essay by Kevin Mernikle:

On July 1, 2021, while visiting our regular family outing location in Smithers, in the Northwest region of the province of British Columbia (BC), I noticed a new butterfly. I identified it as an introduced butterfly species, European Skipper (Thymelicus lineola). I have been visiting this location for six years and this is the first time I’d seen this small bright orange species with distinct narrow black borders on its wings (Layberry et al., 1998).

Hall et al. (2017) indicate that this particular species, when trapped in the lips of the Showy Lady's Slipper orchid (Cypripedium reginae), may interfere with pollination. The European Skipper was introduced into North America near London, Ontario, in approximately 1910 (Layberry et al., 1998). The characteristic of overwintering eggs enabled this introduction.

Guppy et al. (2001) mentions that this species has invaded grasslands, especially timothy hay fields, and its peak flight period corresponds with the native species Garita Skipperling (Oarisma garita), as a result the native species may eventually decline. However, as C. Guppy (pers. comm.) has since noted that European Skippers are strongly associated with timothy hay, which generally occurs in habitats not occupied by the Garita Skipperling.

Swengel et al (2015) indicate that trends farther south suggest a decline in grassland skippers; "both specialized and non-specialized "grassland" grass-skippers declined strongly" (p.279). It is further summarized that a negative impact by European skipper does not appear to explain the trends seen in the prairie specialists, "since both European skipper and specialists declined in the prairie preserves (p. 288).

James et al (2011) summarize that the European Skipper "have reached pest status on hay and pasture grasses in some parts of Canada and the US, where it can be exceedingly abundant" (p.372). Further, "potential impact on commercial crops of Timothy grass in Cascadia needs study as the species is pestiferous in some locations and competition between European skipper and native skippers, such as O.garita and Ochlodes sylvanoides needs study. The impact of endemic natural enemies and the flight period and food plants of European skipper also need study (p.373).

Wagner et al (2021) include introduced species as one of several stressors underlying insect declines. Insects pollinate fruits, vegetables, and nuts. They are biological control for weeds, agricultural pests, disease vectors, and other organisms and decompose leaves, wood and dead animals, assisting with nutrient cycling, soil formation, and water purification. Introduced species can cause ecosystem impacts, including severe native insect declines, with potential local to global ecological and economic consequences (p.2). However, due to the European Skipper primarily using the introduced timothy hay as its larval food-plant (use of other grasses is possible but undocumented), this introduced species may not cause detrimental impacts to native species.

Invasive species have been identified as a threat to ecosystems, habitat and other species. Non-native species continue to increase with efforts to mitigate being non-effective. Impacts from invasive species include predation, habitat degradation, hybridization, and disease agent vectors (The United Nations Environment Programme, 2019).

This observation is a Royal Roads University assignment: EECO586: The Biosphere and Sustainability Consults:

1. Crispin Guppy: biologist, butterfly expert and author of Butterflies of British Columbia (Cris provided comments).

2. Erin Udal: teacher, environmental educator and pollinator enthusiast (Erin provided suggestions).

3. Jennifer Heron, invertebrate specialist, BC Government (Jennifer suggested some articles and provided comments).