We have had plenty of cloudy days this autumn. And when the day was clear recently, I decided to take advantage of it and sit in the sun. By late afternoon, the temperature was mild despite the breeze and I had a pleasant sunlit site.
Cool cloudy days are delightful for hiking in the woods, but a clear day is just as delightful to sit and watch nature during this season. Sitting into a comfortable seat at the lake shore, I waited to see what was happening around me.
I’m joined by a couple of insects still very active at this late date. Small dragonflies — meadowhawks — flit about. Males are red; females are yellow-brown. They fly as though it is a summer day, but their time is limited and they will succumb to the cold temperatures soon.
Not so with the other insects seen here. Several ladybugs are flying in the sunlight and settling for some basking. These beetles will be hibernating soon, going behind bark, under a log or in a crack on the dock that I’m sitting on. And then I note much more is happening.
The late afternoon sun is low at this time of year and looking toward this bright light (never look at the sun), I see numerous threads. These small threads fill many of the branches of small trees and shrubs in the nearby woods. Continuing to look, I see that lots are also attached to the dock itself. These threads are produced by spiders.
We frequently think of webs when noting spider silk, but their silks have many other uses as well. When spiders move, they lay down a thread from their spinnerets (organs near the tail end from which their silks come). This thread is called a dragline.
The purpose appears to be that of safety. If a moving spider were on a twig and gets blown off, this dragline would allow it to hold on or fall slowly and safely. Dragline threads are produced through much of the year, but we usually do not see them. Now in autumn, after the leaves have dropped from the trees, sunlight penetrates more, so, we can readily see the threads.
At this time, however, the threads have a different use. Most of the adult spiders by this late autumn date have died or gone into a cold-weather shelter, but not the young (known as spiderlings). They are dispersing now. This is done by the tiny spiders standing and lifting up their spinnerets. A breeze picks up the exposed thread and carries it off, along with the spider.
This type of spider dispersal where the winds pick up the thread and the spiderling is known as "ballooning." It can be compared to us flying a kite and letting the wind carry off the kite and us. (Spider ballooning is also known as "kiting.") This method of spider flight is very efficient and can carry spiderlings long distances.
Most, however, go only a short way until the threads get caught in another substrate. Leaving the caught threads, the spider proceeds to balloon again. And it is these threads, what are sometimes called "travel threads" (or gossamer), that we see in the late afternoon sunlight. As often happens with spiders, we may see the silken threads, but we usually do not see the tiny spiderlings themselves unless we look very carefully.
There will be more of these threads in autumn. Even on cool days, if we look toward the late afternoon sunlight, we’ll see them.