Observation of the week – August 31 to September 6
Greetings, Butterfly Blitz enthusiasts. While we are nearing the end of the Butterfly Blitz for 2020, its nice to see the continued effort in making observations. This past week we jumped up to 64 total species for this year’s project – four more than in 2019!
Before we get into the OOTW, a quick update on the wrap-up event. Based on the participant survey results, we have decided to hold the event virtually instead of in person. The date is still set for the morning of Saturday, September 19th. Look to your inboxes for an invitation and more details by the end of this week. And please get in touch if you’re not on the email list and want to attend: laura.timms@cvc.ca or lindsey.jennings@cvc.ca.
Now onto our OOTW, a Compton Tortoiseshell seen by participant @betcrooks. Laurie (aka @betcrooks) saw this butterfly at Sheridan Meadows in Mississauga, one of her regular butterflying spots.
As Laurie remarked in her observation notes, Compton Tortoiseshells are having a good year. Larger than usual numbers of these butterflies have been seen here in the Credit River Watershed and across the province. This is in contrast to some closely related species that have been seen in lower than usual numbers, like noted on this Painted Lady that Laurie saw on the same day as the Compton.
Compton Tortoiseshell numbers are known to fluctuate from year to year, but as far as I can tell, no one really knows why. Their reproductive rates and population sizes may be highly dependent on weather and other factors, which could cause such fluctuations.
Like other butterflies that overwinter as adults, Compton Tortoiseshells are one of the first butterflies seen in the early spring in Ontario. Laurie and others often see them feeding on tree sap at Riverwood in March and April, as in this observation. They are known to spend the winter inside buildings such as garages, cottages, and outhouses as well as natural locations such as inside tree holes and under the bark.
Adult Compton Tortoiseshells that emerge in the spring mate and then die, and their offspring emerge as adults in the early summer. Those butterflies live for up to another ten months – through the summer, fall, winter, and early spring!
One way that Compton Tortoiseshells can live for so long is by slowing their bodies down to rest in the summer as well as the winter. This process is called estivation, and it is the summer equivalent of hibernation. Estivating butterflies may periodically emerge throughout the summer to feed, which may occur more often if the weather is particularly hot and dry.
More Compton Tortoiseshells than usual is just one of the interesting butterfly stories from 2020. At the wrap up event on September 19th, we will discuss some of the other butterfly patterns we have seen this summer. What have you noticed this year? Let us know!
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