A few years ago this unremarkable photograph of an unassuming little brown butterfly was taken on the foliage of a Cortes Island butterfly bush (Buddleia davidii).
During the 2017 Bio-Blitz, the image was brought to the attention of Libby Avis and her husband Rick from Port Alberni – both are local experts in matters lepidopteran (especially moths). They immediately realized that the photograph was of a Skipper (Skippers are in their own family Hesperiidae of the order Lepidoptera. The latter comprises the moths and butterflies) and that this particular one could be of great interest to Crispin Guppy, skipper-expert extraordinaire from Whitehorse, Yukon. (Guppy is an unusual, yet strangely familiar name: Crispin’s great-grandfather, Robert John Lechmere Guppy [15 August 1836 in London–5 August 1916 in San Fernando, Trinidad and Tobago] introduced the Guppy, ubiquitous and popular freshwater aquarium fish, to the world.)
Crispin’s reaction was swift and very enthusiastic (for an academic): “Woww!!!!! It is an incredible record.” It turns out that our Skipper had been presumed extinct in our corner of Canada for over 100 years – last previous sighting was on Savory Island in 1913. And now the Silver-spotted Skipper, Epargyreus clarus, had reappeared in a fortuitous photograph!
To paraphrase Mark Twain: “reports of its extinction were greatly exaggerated.”
The questions now were: how many, if any, individuals might be populating Cortes Island? What food- and host-plants might these Skippers utilize?
Out east, where this species continues to be quite numerous, the Black Locust trees (Robinia pseudoacacia) seem to be primary host plants. There are a few Cortes gardens that have these fast-growing trees as ornamentals: could these be enough to sustain a local population of Silver-spots?
A photograph taken at the start of June 2018 and further observations by Barry Saxifrage would lead the way to finding answers to these questions.
In a wonderful and classic example of “gentleman science,” Barry observed several Skippers flying around his sundeck, which is located close to the beach. Sitting in his favourite and very comfortable deck chair by the outdoor table (one is tempted to visualize a martini by his elbow), he noticed that the Skippers frequented a common shoreline plant, the so-called Giant Vetch (Vicia gigantea), and he snapped a few pictures with his iPhone. The results confirmed that, indeed, he was looking at the notorious species!
Where the Skippers had landed on the vetch plants, Barry discovered tiny single eggs—corrugated spheres of 1 mm diameter.
Was the Giant Vetch more than just a convenient location for egg deposits? Could it also be the food plant for the Skippers’ caterpillars?
The author collected a single egg and placed it in a Mason jar full of fresh vetch. Before too long, the translucent egg membrane allowed glimpses of the dark head of the developing caterpillar inside, and soon after that, a hole opened up.
Within minutes, the tiny caterpillar had hatched completely and was marching along the margin of a vetch leaf and began feeding. All this happened on June 12, 2018.
That same day, the little caterpillar (affectionately named Terpi, as in caterpillar) built its first leaf shelter, by rolling up a section of leaf it had cut to size.
Over the following month and a half, the caterpillar grew by about 1 mm linear length every day, putting to rest the question whether Giant Vetch (Vicia gigantea) could sustain Silver-spotted Skippers (Epargyreus clarus). This by itself was a finding of some importance.
Eventually, Terpi’s looks changed: his colour grew ashen, his bright orange eyespots faded, his body seemed shorter and stouter. These were clear signs that the time for pupation had arrived.
Forty-six days after hatching from a tiny egg, Terpi shuffled off its outer skin, a process called ecdysis, by splitting the head in half and wiggling through the crack, leaving behind an exuvia, consisting of the hard head capsule attached to the bunched up skin that had contained the bulk of the soft caterpillar body.
This exuvia has been sent to Crispin Guppy, who will do a DNA analysis to determine whether our Cortes Island skipper population belongs to one of the known subspecies, or whether our skippers might deserve their very own status.
Initially, the pupa was quite soft and vulnerable. But its skin dried and hardened, and Terpi is now hanging in a new little shelter, waiting for the near-miraculous transformations of metamorphosis, which will render the former rotundness of an eating- and growing-machine that is the definition of a caterpillar into a free-flying, beautiful Skipper!
The fact that the caterpillars of Silver-spotted Skippers build leaf shelters to hide in during the daytime makes it relatively easy to find them.
Two additional individuals have been captured and are doing well in their very own Mason jars. Apparently, they are not very sociable, expressing their displeasure when meeting one of their kin by vigorously shaking their heads. One of the two is close to pupation, the second is about halfway there. Two more exuviae are expected to find their way to Crispin. Still not a large sample size, but offering at least a hint of what the genetic diversity of the Cortes Island Silver-spotted Skippers might be. It will be exciting to see what genetic affiliations our local population might have.
So far, all observations are concentrated on a relatively short stretch of beach between Hank’s Beach and Sutil Point. It would be of value to add further records from other locations. Anybody with an interest in the minutiae of the natural world can contribute – and is most cordially invited to do so: please email Christian.
All photographs are the author’s unless indicated otherwise.
Check also our next blog Silver-spotted Skipper Update by Christian Gronau (posted October 12, 2022).