Friday, November 27, 2015

Spring fever in November

The temperature is hovering around freezing; frost on the grass only thaws in direct sunlight. Spiders and beetles have gone into hiding. There are no flies to eat, anyhow.

And now, a tribe of tiny, fragile moths have come out to play in the cold. I found four on one window yesterday, not sleeping; when I touched them, they flew away.

A few days ago, I caught a slower-moving one.

Bruce spanworm moth, Operophtera bruceata. ID'd by the line of single dots at the edge of the wing.

There are several species of similar winter-flying moths around here. They all have one thing in common; if they're flying, they're males, out looking for a mate.

The females don't look (to us) like moths at all: they have just a hint of undeveloped wing stubs. (See this photo in BugGuide.) When they emerge from their pupae, in October or November, they crawl up tree trunks, emitting pheromones, and wait for the males to find them.

Then they lay their eggs one at a time in cracks of the bark. In frozen cracks of the frozen bark. And the tiny eggs develop over the winter, changing colour from green to orange before they hatch in early spring.

I don't think I've ever seen a female, but where the males congregate, they're somewhere near.  I've always found the males on walls or windows; maybe I should be looking on nearby trees for their mates.

(Unfortunately for this guy, my spider had just laid eggs and was hungry, so he went into her box and became a spanworm wrap.)


  1. That should make a big meal for mom and maybe the kids later on. - Margy

  2. I used to see the females crawling up the side of the garage at my parents' place in Vancouver. I had no idea what they were until I saw them copulated with winged moths. See for my comment then, though I think I would've been mistaken about my ID then as I don't recall the females having fethered wing stubs, as the "Winter moths" had...they looked closer to the photos Bugguide has of the Bruce spanworm moth you posted.

  3. Yes, I remembered your comment, and looked it up again, then looked at a lot of photos of females to compare the winter and the spanworm moths. It's always good to have a reason to double-check.


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