Observation of the week – May 22-28, 2021
Our third OOTW for the 2021 Butterfly Blitz is this lovely photo of a Pearl Crescent by @marcjohnson.
Marc will be familiar to those of you who participated in the 2020 Butterfly Blitz. Working with his family, Marc won the prize last year for the most observations. The Johnsons traveled all over the Credit River Watershed in search of butterfly species in different habitats, and even made a special Canada Day challenge for themselves to spot as many species as possible.
To see this butterfly, Marc and his family went to one of their favourite butterfly spots – an area of Silver Creek Conservation Area where they’ve had good butterfly success in the past.
Marc says: “I netted the beast knowing it was a crescent of some type given the colour, size and slow flight pattern just above the vegetation.” There are three species of crescents in our area – Pearl, Northern, and Tawny. To identify this one, Marc noted that the butterfly “was very dark on the upper side, with lots of thick black veining, including on the upper side of the hindwing. It seemed like the stereotypical Pearl Crescent to me. It was nice to see one that looked so clear as I struggle a little with separating the crescents.”
Although they’re pretty, Marc admits that crescents are some of least favourite butterflies. I will admit that crescents also confuse me. And we are not the only ones that feel that way.
Pearl and Northern Crescents used to be considered one species and were only identified as distinct in the early 1990s. Most field guides comment on how difficult the species are to separate, especially females. BugGuide even suggests that the identity of published photos of crescents is debatable! Everyone seems to use slightly different characteristics to tell them apart, and it can be frustrating to feel like you’ve figured it out with one butterfly only to have it fall apart with the next one.
Sometimes its can be more rewarding to admit that you just don’t know. While researching this post, I came across this lovely little bit of writing about the virtue of uncertainty, specifically relating to Northern and Pearl Crescents. The author, Bryan Pfeiffer, suggests that not knowing the answer can keep us humble and remind us of all the questions that remain to be answered about insects, biology, and science as a whole!
Its possible that future research will lead to better separation of crescent butterflies, so I will be sure to take the best photos I can every time I make a crescent observation. But for now, I’m also resolving to be happy with calling them crescents and to embrace that little bit of uncertainty.
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