Wednesday, August 14, 2019

Happy campers, tenting

There's an old apple tree beside the path at Oyster Bay. I stop there often, to look at lichen in the winter, and apples in the spring.

Little green apples, late June

I stopped again the other day. The apples should be ripe by now, and maybe I could pick a couple. But someone had been there before me.

Yes, the apples are ripe. And the tent caterpillars are busy.

The dark mass in the centre of that tent is made up of amassed caterpillars. If you click and zoom in, you can see their outlines.

Another branch; a feeding site, not used for overnight. The caterpillars huddle together for warmth, and this was a cool afternoon.

I pulled a couple of leaves away from this clump, exposing a few of the caterpillars inside.

Western tent caterpillar, Malacosoma californicum. Colours vary, from black to green to orange, and even pale blue, but all have that lengthwise stripe and long hairs. And all build the same webbed tents.

Another one. He seemed to be asleep until I touched him with a blade of grass. Then he hurried to get back under cover.

Caterpillar poop in a feeding site.

Leaves consist largely of nondigestible components, and it has been estimated that tent caterpillars void as fecal pellets nearly half of the energy they ingest. As a consequence, a colony of caterpillars produces large quantities of fecal pellets. (Wikipedia)

Skeletonized leaf, with webbing.

Western tent caterpillars build their tents on willow trees, cottonwood, apple, plum, cherry, and oak. This colony is on apple; later, I found another tent on a bitter cherry tree (Prunus emarginata).

Bitter cherry twig with feeding tent.

The trees are not really harmed. The caterpillar populations increase and decrease in cycles of from 6 to 11 years. In between, the leaves grow back and the tree thrives. The moths and their hosts are native species, and they are well adapted to each other.

I didn't get any apples. Somehow, all the apples on the trail side of the tree were missing, although the caterpillars hadn't touched those branches. On the far side, there were ripe apples, all too high, and too surrounded by webbing, to reach.


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