We observed a delightful butterfly in the garden this morning which turns out to be a foreign immigrant (like us) … Thymelicus lineola, known here as the European Skipper and in the UK as the Essex Skipper.

Needless to say this is an introduced species, though there are plenty of native Skippers around too. Accidentally introduced in 1910 via London, Ontario and has spread across southern Canada and into several northern US states. In many parts of the Northeastern United States it is the most abundant skipper. Eggs are laid in strings on the stems of grasses where they remain over the winter.

J remembered having recently seen an interesting post from the Ontario Field Botanists (a very erudite group of botanisers far above my pay grade). The writer wrote thus:

I went out to look at some Showy Lady’s Slippers in Tiny Township, Ontario, today, June 24. 2021.

Looking into one of the blooms I could see 2 deceased European Skippers inside. European Skippers, known in their native Europe as Essex Skippers, are a non-native introduced pest species in North America.

As far as I know, Lady’s Slippers are not carnivorous. So I did some reading to find out what was going on here. This is from a University of Wisconsin website:

Speaking of orchids, the BugLady found an interesting paper about the effects that foraging ESs (European Skippers) have on seed production in the spectacular Showy Lady’s-slipper orchid. Orchids are famous for the tricks they play on potential pollinators and the hoops they put them through. A number of orchids are pollinated by “naïve bumblebees” (a term that tickles the BugLady). The orchids advertise their flowers by odor or color; the bees enter, and they find no nectar reward, but they leave bearing pollen. It takes a few unrewarding visits before an individual figures it out and moves on to more rewarding flower species, but there are always more naïve bumblebees out there.

In the case of Showy lady’s slippers, pollinators are lured into the slipper and are trapped in it because the tissue around the lip’s opening is folded into the flower. The only way out requires them to squeeze past hairy structures that first relieve them of any pollen they are carrying and then deposit new pollen on them before they reach the narrow exit – with no nectar for their efforts.

In one study, the majority of Showy lady’s slipper flowers in a study bog in Ontario contained one or more dead ESs, which can’t escape by the normal routes (one flower held seven!). Males outnumbered females, because male ESs emerge from their chrysalis earlier than females. Once an ES gets into the flower, pollination by the normal pollinators – leaf-cutter bees, syrphid flies, and a few small beetles – becomes difficult-to-impossible and seed production plummets. If the ES can’t escape, like the naïve bumblebees, it can’t learn to bypass the orchid.

So – rising populations of ES have the potential to impact Showy Lady’s slipper populations.

Knowing what I know now, I should have probably cleaned out that flower. Next time.