Out in the Cold

It’s early morning. Still dark. Outside temperature is about 0° C and there are several Bruce spanworm moths on the window. The other evening, only a few degrees above freezing, we counted nearly 6 dozen on that same window, all drawn to the kitchen light.

As I discovered, these moths are unusual in several ways — not the least of which is their ability to remain active in cold weather.

Greg Pohl, Insect/Disease Identification Officer with Natural Resources Canada, explained how this is possible:

“Winter moths are quite remarkable. They’re adapted to fly at temperatures as cold as -3°C. They put quite a bit of their energy reserves into antifreezing chemicals in the bodies, and they also “shiver” to warm up their bodies and flight muscles to the point that they can fly. So even though they’re “cold blooded”, they have some ability to warm their bodies. They’re very highly adapted to fly late in the fall, and thus avoid many predators. But those survival skills wouldn’t likely be developed in warm-weather day-flying species like monarchs.”

Male Bruce spanworm moth

If not for finding these nondescript moths in such cold temperatures I might have paid them little heed. Lesson learned: sometimes the plainest wrapping holds the biggest surprise.

Bruce spanworm   Operophtera bruceata

What Are They Thinking?

We’ve had cold nights, cool days, ice on the windshield and the deck, several small snowfalls and now this: a large hatch of moths.

What the heck is going on? This ain’t the right season to be flying around.

Or is it?

The moths gather by the dozen at night on our uncurtained windows. During the day they flutter and flop around the yard, along the gravel road and in the sunbeams in the woods. Getting clear photos of them has been a challenge as they never really stop for more than a moment. They’re in a hurry.

Bruce spanworm moth

Turns out they’re doing exactly what they should be doing at this time of year. They’re Bruce spanworms and they’re “late season” moths. No kidding. Seems the drop in temperature is what kicks off the mating season.

Another quirky characteristic — all the ones with wings are males. Females are wingless. This frenzy has been going on for a couple of weeks. There’s no time to eat, only to mate and lay eggs that will hatch next spring.

Get busy guys.

Bruce spanworm moth

Bruce spanworm   Operophtera bruceata  

Taken for a Loop

This has not been a good summer for moths. Few have come to the porch light or landed on uncurtained windows after dark so it was quite a surprise to find this nocturnal moth feeding in my garden in daylight.

It’s one of the looper moths — named for the caterpillars that curl into loops as they move, rather than crawling. They feed on dandelions, as well as plantain and nettles all of which grow in our yard. Maybe they have been here all along, and I’ve just never seen them.


I was intrigued by the little tufts of hair along its back and the two white spots. They helped narrow down the identification and certainly make this moth memorable.

Unlike some moths that have a single common name (or none at all) this one has several — two-spotted looper moth, twin gold spot and double-spotted spangle. Take your pick. If you’re scientifically inclined you’ll know it as Autographa bimaculata. Once you get the hang of it, that last one kinda rolls right off the tongue. 🙂

Two-spotted looper moth   Autographa bimaculata



Egg Case

The Tortrix moth infestation that occurred this spring was of almost biblical proportions. Many of the aspen forests were completely denuded by the ravenous caterpillars (aka larvae).

They pupated next, then after a short respite, the adult moths appeared. Thousands of them. And of course, their main goal was mating and egg laying, which they did in grand fashion.

In fact, so intense was the drive to lay eggs, they did so in the most unusual places. We discovered egg cases, like the one above, on the windows of the house, on the siding and on the vehicles.

Many of these eggs never hatched. The ones on the south-facing windows, for example, simply got too hot. But not before some activity occurred.

The egg cases were all about the same size as this one — 1.3 cm or so long (0.5 in). The original egg case was a lime green — some of that is still visible. I’m assuming it was plant material to feed the newly hatched larvae.

The comma-shaped figures are the newly hatched black-headed larvae. Some of the cells are empty — perhaps they survived?

Mother Nature’s Natural History Show is a wonder. Glad I caught this episode.

Large aspen tortrix   Choristoneura conflictana

Here’s Lookin’ At You, Kid

I don’t get to see the underside of life very often. Bugs and butterflies don’t take kindly to being upended.

Finding this large aspen tortrix moth on my window was a perfect opportunity to check out the undercarriage. Quite different from the bland topside view — this is right out of a sci/fi movie.

This spring its larvae devastated huge swaths of aspen poplar, eating all the leaves until limbs and twigs were bare. Their silk festooned the woods, draping over everything below, right down to the forest floor.

The trees are slowly recovering and the moths are disappearing. Cycles within cycles.

Large aspen tortrix   Choristoneura conflictana

The Silk Makers

I wrote recently about The Silk Road. This is the rest of the story.

How many mouths does it take to eat a tree?  Not the wood. Just the leaves. All of them.

That’s what has happened in our corner of the world. Most of the aspen poplar have been completely defoliated by armies of small black caterpillars.

The caterpillars, or larvae, are the second stage in the life cycle of the Large Aspen Tortrix.  The name Tortrix comes from a Latin word meaning to twist. When you see the leaves they’ve been feeding on, you can see why that name was chosen.

These photos and captions tell more of this tale …

Some pupae have already split open, releasing the adult moths. I imagine we’re in for quite a show when the big hatch happens.

We’ve had defoliations in the past, but I don’t recall anything like this — it stretches for kilometres in all directions.

Although this feeding frenzy sounds disastrous for the aspens, it’s not as gloomy as one might expect. The trees are already sprouting new leaves and before long will look more like they should at this time of year.

Conditions this year are different. Winter was mild. Spring came early. It turned hot. Rainfall has been little and sporadic. Are we seeing the effect of climate change? Or merely a brief climatic blip?

It’s an ongoing evolutionary dance as we each strive to adapt to our world.

Large aspen tortrix   Choristoneura conflictana
White spruce   Picea glauca
Trembling aspen   Populus tremuloides