City Creek Nature Notes – Salt Lake City

November 13, 2016

November 13th

How Nature Goes to Sleep

2:00 p.m. Last Friday was the sixth or seventh in a series of clear fall, warm days. During an afternoon jog, there were many unusual insects on or crossing the road, and at mile 0.6, there was a small golden iridescent beetle. It was a Golden Tortoise beetle (Charidotella sexpunctata). At mile 0.4, a yellow lady bug with large black spots on its back, landed on my hand. It was a Squash lady beetle (Epilachna borealis). At mile 0.3, there was what appears to be a Common stonefly (Zapada cinctipes) with its long forked tails, but the colors its abdomen are wrong: the segments are divided by white stripes. A sole European paper wasp flies by.

It is a month since the first day of Fall (Sept. 22nd). In the Fall, nature is going to sleep for the winter. Before visiting the canyon on a daily basis, I used to be wrapped up in the work day and did not notice the subtleties in the change of seasons. I thought the progression from Fall to Winter to be abrupt; it is an overnight affair that comes with the first deep snow. Now, having been in the canyon everyday this season, I see a longer pattern that is driven by the rate of change in the length of the day and astronomy of the Earth’s orbit.

At the equinox, the rate of change of the length of day is at its highest; the length of days decrease by at most four minutes per day. That initial rate of change causes a shock to the atmosphere and results in early Fall storms, and trees in the canyon respond by dropping their leaves. Storms come followed by a period of warm weather, and the insects not killed by initial cold storms respond by migrating to some new location to search for the less available food or to seek a new location in which to hibernate over the winter. The length of these warm periods lengthen as the rate of change in the length of the day decreases, although the absolute length of the day continues to decline. The few remaining insects rebound, but then their numbers are reduced to a lower absolute level by the next storm. This Fall cycle where storms are followed by longer periods of warm weather, continue until some tipping point is reached as the absolute length of the day fails to hold back the first frost and-or the first snowfall. The length of the day continues to decline until the first day of winter near Christmas.

The result of this cycle are days like last Friday, where unusual insect refugees are found on or along the road. In the summer, they are hidden by dense foliage, and although they are more numerous in the summer, they do not have to travel far for food. Now, the survivors chance leaving the protection of the leaves and venture far for food, and they are more easily seen. Some fail and lay flaying on the road. Several unidentified spiders were seen on the road, and they take advantage of this late season bounty.

Nature goes to sleep like an insomniac. It does not go to sleep abruptly. In the Fall, nature tries with the first heavy storms to fall asleep at once, then partially reawakens, and tries again for slumber. It repeats this cycle until true winter overtakes it, and forces it to rest.

Humans, even those of the modern post-industrial world, are part of this astronomical cycle: we celebrate our holidays in response to the change in the length of days at cross-quarter days. Today, it is about a week past the cross-quarter day of the Fall – Halloween or All Saints Day, and the rate of change in the length of days has reduced to about one minute per day. Seasons are about ninety days long and cross-quarter days occur about forty-five days after the start of the season or forty-five days before the end of a season. The other lessor holidays occur that occur near cross-quarter days are Groundhog Day in the winter, May Day in the spring, and Labor Day in summer. Major holidays are near the solstices and equinoxes when the rate of change in the length of the day is at its greatest.

In his “Journal” on November 13, 1851, Thoreau observes that after a snowfall, crickets and mosquitoes can no longer be found.


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