Winter Moths and Forest Artwork

Two Fascinating Findings this Morning.

We took today’s walk (we make it a rule to walk somewhere every day – got to fight off this ageing business) in the Arboretum which apart from a couple of dog walkers we had to ourselves. When we set off along the trail there were ice pellets falling – not for long, thankfully, which made a surprising amount of noise as they hit the carpet of leaves on the ground. No doubt at all that winter is arriving.

One very striking thing today as we walked around was a large number of small, brownish moths fluttering all over the forest a few feet off the ground. The temperature was about +2C and although I was aware that some insects have evolved to take advantage of the lack of predators at this season I have not seen the numbers that are around today. I didn’t have a camera to photograph them and anyway they never settled even if I had so we made a note to look them up when we got home. Well, it seems this is the day for them in other places too because a member of the Ottawa Field Naturalists Club (a couple of hour’s drive west of here) had seen the same phenomenon in her morning’s walk. She knew what they are however which saved me some time digging out the information.

These insects are Operophtera bruceata or the Bruce Spanworm Moth, also known as the Hunter’s Moth or Native Winter Moth. As I said, I didn’t get a photo so I have posted someone else’s to the right for reference. Only the males are flying, the females have such a large egg mass they are incapable of doing so. The eggs overwinter and then larvae hatch in the early spring. The caterpillars primarily feed on the buds and nearly unfurled leaves of sugar maple and American beech. They have also been recorded on willow and various other deciduous trees. After feeding for a few weeks, the late instar caterpillars drop down to the soil and build a cocoon. They pupate until the late fall or early winter when they emerge as adults – which is what can be seen today.

The other observation today was down where the main trail meets the field with the Branchery in it. The structure at first looks like a pile of branches, albeit neatly stacked, but as you get closer it is seen to be a circular fenced area very akin to a traditional sheepfold. However we have no sheep and there is no entry to the ‘fold’ so unless someone is doing a bit of freelance squirrel rustling we assume this is a bit of freelance forest art. It’s really well done and worth looking at.

The ice on the puddles was surprisingly thick and the forest was cold and calm and just what we needed. If you live near here pop over and check out the moths and the squirrel-fold.