If you spend enough time watching butterflies, you may notice different species are more common at different times. The spring and summer waves of butterflies emerging month after month is an unfolding pattern Alberta naturalists look forward to each year.
Alberta’s peak butterfly season is from the beginning of June to the first half of August, but these charming insects can reliably be found from April to mid-October, depending on the weather. Different species have evolved various timing strategies for their life cycle, especially when it comes to making it through the winter.
Some butterflies tough out the colder months as eggs, others as caterpillars or pupae, while a few species overwinter as adults. Two common Alberta butterflies that hibernate through the winter as adults are the Mourning Cloak and Milbert’s Tortoiseshell. Adults of these species that emerged from their pupae in July find sheltered places to tuck in until April when they emerge with worn and faded wings. During warm winter days, they’ll sometimes come out for a short flight in the sunshine before going back down to rest again.
In early May, the small but lovely ‘blues’ like the Spring Azure start to appear, followed by the common Silvery Blue later in the month. Around this time as well, the ‘whites’ and some Anglewings appear. The former is a familiar family of white butterflies found throughout the province, the latter is a common orange-and-black variety with scalloped wing edges. Late May to early July is prime time for the big yellow Swallowtails that soar through poplar woodlands, as well as the drabber Common Alpine of open meadows.
In June things really start to get busy. The small, stubby Skippers begin darting around the woods and grasslands. Bigger forest species like the glorious White Admiral and more cryptic Northern Pearly-eye with its multiple eyespots float among the poplars. More varieties of ‘blues’ like the Western Tailed Blue emerge, as do the small orange-and-black crescents.
By early July the new adult Mourning Cloaks and tortoiseshells are joined by a host of Fritillaries. These beautiful orange butterflies come in two main varieties: the smaller, more subdued ‘lesser fritillaries’ and the big, silver-spotted ‘greater fritillaries’. Telling species in each group apart takes some skill, so don’t feel bad if you only know them as ‘some kind of fritillary’ at first. Through July more Skippers rotate through, and species of grassy areas like Ringlets, Common Wood Nymphs, and Clouded Sulphurs are on the wing. Cabbage Whites remain common as ever. Albertans can also hope for sightings of migratory species like Red Admirals and Painted Ladies. On good years in the southeast, Monarchs can also make a seasonal appearance.
August is when things start to slowly wind down for butterflies. Whites and Sulphurs remain common, and Wood Nymphs and Anglewings can be found as well, but the overall species diversity isn’t what it was a month before. Some species from earlier in the year have a second generation that emerges in August, but they tend to be less common or simply lie low until early fall.
Late summer to early fall is pretty quiet for butterflies. If the weather holds out, though, things like Anglewings and Mourning Cloaks can still be found well into October, eating from the last remaining flowers and tree sap before either dying or hibernating. On good years this can be as late as Thanksgiving weekend at least.
Once the temperature drops and the snow starts to fall, Alberta’s butterfly season is basically done. This can make our dark winters feel all the more endless as naturalists wait for these colourful little insects to return.
Did you know...Butterflies are easiest to spot during calm, sunny conditions around the middle of day – this is when they're most active. But you'll see them in the early evening on hot days and on warm, cloudy days too.
Nick Carter is an Edmonton-based photographer and naturalist. See more at naturenickphotography.com