Whirligig beetles prepare for the cold
Like many Northlanders who have access to a lake, I frequently go to the nearby bay. This aquatic site proves to be a regular source of recreation and relaxation. Besides paddling here, I find that sitting by the bay is a great way to observe the changing seasons. I watched as the ice went out last spring. This was followed by the return arrival of loons and ducks. Later, mergansers and geese families moved by here on their way to growing through the summer. The warming brought out the painted turtles to bask on logs. Some climbed on land to lay eggs while gray tree frogs, toads and leopard frogs place their eggs in water.
Many of the summer days were filled with flights of dragonflies that basked and hunted in the sunlight after having emerged in the darkness of the night before. Phoebes, kingbirds and swallows moved in to feed on the myriads of insects that also call this bay their home. Going for larger prey, the bay was also visited by herons and kingfishers seeking fish dinners.
As I returned in the evenings, I watched as the local muskrats and beavers made their rounds. Food to these aquatic rodents is plants along the edge. And as darkness creeps in, the local big brown bats circle over the bay to gather their share of the available insects.
When summer peaked, this also became the time to hear the daily calls of the summer frogs, mink and green frogs. Summer became late summer and the yellow pond lilies were joined by white water lilies flowering in the bay. On shore are arrowheads, bonesets, jewelweeds and asters in bloom. A few of the shoreline red maples are in their red attire and birches are more yellow each day.
The months slipped by and soon we were wandering through September. During a recent trip to the bay I noted that the young loons are now adult size, though in a different plumage. Migrant warblers were on the nearby trees. Both the resident spotted sandpipers and the migrant solitary sandpipers were moving on. Loud flocks of geese and families of sandhill cranes were hard to not notice as they flew over. Looking out in the lake, I was surprised to see a group of otters as they actively fed. With all this happening on a September day, it is easy to overlook the smaller and quieter phenomena that are present as well.
During my summer visits to the bay, I would look out to see a raft of small insects on the water's surface. I was able to identify them as whirligig beetles. They stayed in the center of the bay except for when a strong wind sent them to the shelter of a nearby log. These insects colonize a part of the bay that we are likely to overlook, the surface. Not below water or flying over, they live on the film of this wet world. They are not the only critters to be in this limited site and often I have noticed water striders, an unrelated insect that also walks on water. Also there is a large spider, the fishing or dock spider that spreads legs to move over the surface. Several kinds of tiny insects live here or travel at this site as well.
But it is the whirligig beetles that keep my interest as we move towards fall. They get this unique name for their unique way of defending themselves. When in danger or approached by a possible threat, they go through a quick series of fast circular motions. They become hard to see or catch. Also unique is that they use front legs for swimming instead of rear as many other water dwellers do.
The list of strangeness continues. Researchers have found that their eyes are divided so that they can see above and below them at the same time. As predators, they feed on any food that they can reach. This may mean traveling over the lake. I have noticed that hundreds may be in the bay one day, few the next and then the mass returns. Apparently, they will move at night when the lake is calm.
Now as the weather gets cooler, their water surface home will no longer be a safe place to live. What can they do? I have noticed that during recent days, they are moving closer to shore. And as the days begin to freeze, they will get right up to the shore, maybe onto plants, maybe in the mud or perhaps just under the shoreline leaves, where they go into hibernation (called diapause with insects) for the winter.
Each day in September they are closer to that wintering goal. (I once saw whirligig beetles still active on the water when ice was just a few inches from their moving bodies.) When waking next spring, they will reproduce and by next summer this bay will again filled with these dark half-inch oval insects swimming on the surface.