Observation of the week – May 15 to 21, 2021
The second OOTW of the 2021 Butterfly Blitz is this Wild Indigo Duskywing seen by participant @bugsrock.
Trudy (aka @bugsrock) managed to snap this photo while on an extended stakeout. She says: “That shot was taken in the valley near my neighbourhood early on a Saturday morning after spending quite some time staring at the meadow hoping to see butterflies and photographing lots of other bugs. Butterfly photography takes a lot more patience than the photography of other bugs! I sat still for quite some time in the area where I had seen the Wild Indigo Duskywing and waited to identify an area where it tended to land and then moved into that area to wait.”
Once she had the picture she had been waiting for, Trudy worked on figuring out what butterfly it was. “I used iNaturalist to ID to the level of Duskywing and looked at the ROM guide but needed help from an expert on iNat to get it to the next level. I’m still not sure how to tell the subtle differences between all the Duskywings!”
If you attended the training webinars on May 8th, you will remember that I said that Duskywing skippers can be hard to identify. They are all dark brown with some amount of gray and light brown mottling and white spots on their wings. And they tend to fly away quickly when disturbed, making them hard to photograph.
There are ten species of Duskywings in Ontario, but only four are likely to be found in the Credit River Watershed. Of those four, the Wild Indigo Duskywing is by far the most common – but it was not always that way. Wild Indigo Duskywings used to be limited to a few spots in southwestern Ontario. So, what happened?
The caterpillars of Wild Indigo Duskywings feed on wild indigo plants (Baptisia tinctorum) and other related native species like lupines. But in recent decades they have also started feeding widely on crown vetch (Securigera varia). Crown vetch is an introduced species; it was widely planted across Ontario and other parts of eastern North America for roadside erosion control starting in the 1950s.
When relying on their native host plants, Wild Indigo Duskywings were found in open woods and barrens and were never that abundant. But with a plentiful new food source spread throughout their range, they have become much more common and are found in almost any open habitat.
Wild Indigo Duskywings are not the only native butterfly species that have added an introduced food source to their diet. This table lists 29 species in Massachusetts that are known switchers, most of which also occur in Ontario.
Although they have become much more common in our area, do not assume that every Duskywing that you see is a Wild Indigo Duskywing. We also have Juvenal’s, Columbine, and Dreamy Duskywings – the first two of which are easily confused with Wild Indigo Duskywing.
To help with the identification try to get photos from different angles and note the surrounding habitat and which host plants are present. And, like Trudy did, you can get help from experts and other Butterfly Blitz participants on iNaturalist. Do you have any Duskywing identification tips to share? Please let us know in the comments!
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