Emergence of Spring Butterflies and Mustard Whites

Eastern Pine Elfin

Eastern Pine Elfin

So far it’s been a strange spring. It took a long time to warm up to 0°C and then a while longer to warm up to double digits. Early April was cold and very windy; it didn’t get consistently above 10°C until April 21, but even then it was too gusty in the afternoons to go looking for butterflies. My first butterfly of the year was a Mourning Cloak seen on April 5th at the Rideau Trail on Old Richmond Road. It was a beautiful day of 13°C, and I figured I had a good chance of seeing my first butterflies of the year there….though it was a toss-up as to whether it would be a Mourning Cloak or an Eastern Comma, both of which hibernate as adults in woodlots. While I saw a few more Mourning Cloak in mid-April, butterfly season didn’t really start until the second last day of the month.

The Mourning Cloak has been my most-observed butterfly species so far this spring. I’ve seen many in Stony Swamp, Mud Lake, Richmond Conservation Area, and even one flying through my own backyard. They are large and conspicuous in flight, with distinctive brown wings edged in yellow. They like to perch on the ground or on tree trunks, where they often feed on sap.

Mourning Cloak

Mourning Cloak

When they close their wings, the cryptic undersides looks like a dead leaf or part of the tree trunk. This helps them to avoid predators such as flycatchers and dragonflies. Mourning Cloaks mate soon after emergence; males defend small territories in sunny woodland clearings or forest edges where they wait for females. The female lays over 30 eggs in a single mass on a tree or shrub. The caterpillars hatch in June, feed, and eventually disperse once it comes time for each individual to form a chrysalis. New adults emerge later in the summer, but are not active until early fall. They undergo a summer hibernation known as aestivation, which prolongs their lives by reducing predation and wear and tear on their bodies.  These are the adults that will emerge on warm days the following spring, giving them a lifespan of over 10 months!

Mourning Cloak (underside)

Mourning Cloak (underside)

On April 29th I saw my first Compton Tortoiseshell at Sarsaparilla Trail. Later that day I saw a few more at Rideau Trail just down the road. Two of them were feeding on sap dripping down a tree trunk, something I haven’t seen before. I also saw a few others flitting through the woods and photographed one on the boardwalk. These butterflies are related to the Mourning Cloak, both of which are found in family Nymphalidae. They are often called angle-wings because of the irregular edges to their wings. The Eastern Comma is included in this group, and all of them overwinter as adults. Unlike the brown Mourning Cloak and the orange Eastern Comma, the Compton Tortoiseshell appears brownish-orange with white spots when seen in flight.  They, too, like to perch on the ground or on tree trunks, making them easy to photograph.

Compton Tortoiseshell

Compton Tortoiseshell

Compton Tortoiseshell

Compton Tortoiseshell

Despite being one of the earliest butterflies to emerge, it took me until May 10th to see my first Eastern Comma. I photographed one at the Richmond Conservation Area near the parking lot after having three additional orange commas fly away too quickly to identify.

Eastern Comma

Eastern Comma

Another surprise for me this year was seeing Henry’s Elfin before Northern Spring Azure. Normally I see these tiny blue butterflies darting along wooded trails a few days before looking for the brown-coloured elfins in Stony Swamp. Both species are members of the gossamer-winged butterfly family, and overwinter in the chrysalis stage so that they are ready to emerge as adults once the weather consistently warms up. Two were in the same spot where I’d seen them last year in Stony Swamp, just beyond the last boardwalk at the Rideau Trail on Old Richmond Road. I was surprised to see them, although the date – April 29th – was about when I’d expect them to be out.

Henry's Elfin

Henry’s Elfin

Although I didn’t see any azures, I had some luck with some non-butterfly species that day, including several Greater Bee Flies and a flower fly that flew off before I could photograph it. Bee flies are harmless pollinators that look fearsome due to the sharp, mosquito-like proboscis attached to the head; this is not a stinger, and is used solely for sipping nectar from flowers. They are named for their resemblance to bees, a common type of mimicry in the insect world that makes harmless insects look more fearsome to would-be predators. They can even buzz like bees, but on closer inspection have a single pairs of wings (instead of two pairs), long and skinny legs, short antennae, and eyes that meet on top of the head. The Greater Bee Fly can be identified from other bee fly species by the pattern of the wings – it is the only one in our area that has a dark leading edge and a trailing edge that is clear and colourless like glass. The fuzzy body looks like a piece of lint, and the “fur”, or pile, is usually a shade of brown or yellow. The Greater Bee Fly is common and widespread in Ontario, where it lives in woodlands or forest edges, feeding on the nectar of early spring wildflowers.

Greater Bee Fly

Greater Bee Fly

I was happy when I finally found a flower fly later at the Beaver Trail the same day. Flower flies are also bee mimics that are important pollinators; they can be found in many habitats, including your own garden! This one was a Black-shouldered Drone Fly, a species that seems to be common in forests, especially those with marshy areas. Flower flies are also called hover flies, as they often hover in one spot with their wings beating so fast they become invisible.

Black-shouldered Drone Fly

Black-shouldered Drone Fly

I finally saw my first Northern Spring Azure on May 1st at the Richmond Conservation Area where I found a single individual. I had more luck with both Henry’s Elfins and the azures along a side trail at the Watts Creek trail/Greenbelt West pathway on May 8th – there I saw at least 10 Henry’s Elfins and at least 6 azures along a section of about 40 metres! While the Northern Spring Azure is the more abundant and widespread of the two species, I have never seen that many elfins in one spot. There was a time when they weren’t very common in Ottawa at all!

Henry's Elfin

Henry’s Elfin

Northern Spring Azure

Northern Spring Azure

By this time I was only missing one early gossamer-winged butterfly in my part of Ottawa, the Eastern Pine Elfin. They are small, exquisitely patterned orange butterflies that are found in areas with mature pines…any place where you hear a Pine Warbler singing is a good place to look for these low-flying elfins! The Beaver Trail is a great place to find them, and I usually see at least one on the extension to Lime Kiln Trail every spring. Only one was present on my visit on May 12th:

Eastern Pine Elfin

Eastern Pine Elfin

Also by this time I had seen my first Cabbage White flying over my lawn; these are the common medium-sized white butterflies that are abundant in city gardens, fields, and open rural areas close to people. They are also not native, so finding one deep in a trail system far from human habitation is always a disappointment. The most common native white butterfly in our area is the Mustard White, a species that lives in the woods and feeds on nectar from flowers in the mustard family, among others. I used to see them from time to time in the woods of Stony Swamp, usually single individuals. Marlborough Forest is a better spot to see them, though I have seen Cabbage Whites there as well. Both of these species over-winter in the chrysalis stage and emerge once the real spring weather arrives.

I wasn’t expecting to see any Mustard Whites this spring as I have been staying close to home, so I was surprised when I saw several individuals at Sarsaparilla Trail and one individual at the Rideau Trail on May 11, 2022. There were between 8 and 10 individuals fluttering through the woods, and I found myself photographing them every time one landed near me.

Mustard White

Mustard White

From above, this butterfly is very plain with bright white wings marked by gray veins that are barely visible. Unlike the Cabbage White they have no dark spots or dark edge on the tip of the wing.

Below they are much more attractive, with greenish-gray veins lining the wings and a bright yellow spot near the shoulder. These veins are prominent in the generation that emerges in the spring; a second generation that emerges later in the summer lacks these veins almost entirely.

DSCN2751-2

Adults take nectar from a variety of flowers, although it is believed that they prefer nectar from their host plants. These include plants in the mustard family (Brassicaceae), such as Two-leaved Toothwort, Cuckoo Flower, and Rock Cress. They also take nectar from the highly invasive Garlic Mustard, an aggressive plant that quickly takes over areas in which it is found. However, this plant does not provide sufficient nutrition for the caterpillars to complete their development, which may be one of the reasons this species is declining. Although there are studies that suggest this butterfly may be adapting to the foreign plant, the Mustard White is being out-competed by the non-native Cabbage White, whose larvae are able to use them to complete their life cycle and thrive.

Mustard White

Mustard White

I was so happy to see this species here, and so many individuals, that I returned nine days later. There were still plenty of Mustard White butterflies around, at least eight or ten individuals again. They were nectaring on a variety of plants, including dandelion and Garlic Mustard:

Mustard White

Mustard White

Mustard White

Mustard White on Garlic Mustard

I was also thrilled to see a White-striped Black Moth on a sunny dandelion; these small moths are often common in wooded areas, though they are difficult to photograph as they keep to the shade. This is not only the first time I’ve seen one taking nectar from a flower, it’s the first time I’ve seen one land in the sun!

White-striped Black Moth

White-striped Black Moth

It’s been great to see the first butterflies and insects of the year as they emerge, particularly the difficult-to-find Mustard White. Hopefully they are able to thrive at Sarsaparilla Trail and a second brood will emerge later this summer!

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