Numbers are everywhere in our lives from phone numbers, to addresses, to bank accounts, and a million other places. Numbers appear in nature too from the distinctive number of petals on a flower to the number of segments in a dragonfly’s abdomen.
Biologists use numbers to group and to differentiate various species of plants and animals. Sometimes numbers are built into the common names of the wildlife we see at the cottage from the two-striped grasshopper to the eight-spotted forester moth to the twelve-spotted dragonfly. Following are just a few White Lake examples.
To begin, the number two is used to name the two-striped grasshopper. We see these grasshoppers throughout summer from June when we first see nymphs, to late July when the adults appear. We continue to see these grasshoppers until cottage close-up in October. Before winter, the adult female lays her eggs in the soil to hatch by late April the next year. Considered by many to be a pest species, we do not see enough of them to think they present a problem, but the farmers and gardeners in The Valley may disagree.
One of our favourite dragonflies is the four-spotted skimmer, in part because it is one we have learned to identify, but also because it loves to eat mosquitoes! To our eyes, the shape of the abdomen, broad near the thorax and tapering almost to a point at the tip is distinctive. None of the books describe them that way, though; rather, they focus their descriptions on the abdomen colours, the golden brown of segments 1 to 6, and black from 7 to 10, as well as the four spots on the wings. (Segment 1 is closest to the thorax.) Described by some as a spring dragonfly, the earliest we have seen one is May 28th and the latest July 1st. It seems to prefer ponds and slow-moving rivers. Remember, they eat mosquitoes!
We love the brilliant metallic green colour of the six-spotted tiger beetle with its distinctive white spots, three on each elytra. We have seen them at the edge of the forest or the edge of the road, usually early in the summer. The adults overwinter and mate the following spring. This mating pair was photographed late in May. The female lays her eggs in the soil. After the eggs hatch, the larvae burrow into sandy soil which we have in spades. Well, we have sand in pockets of bedrock. We love to see the beautiful six-spotted tiger beetle because it feeds on other insects, helping keep a balance in the yard and forest.
The number eight is used to identify the eight-spotted forester moth which we see in the photograph below being eaten by a goldenrod crab spider. Clearly the small spider punches above its weight. The eight-spotted forester moth has two spots on each of its four wings, and tufts of orange on its legs. A glimpse of orange tuft can be seen on the right fore-leg in this photograph.
Another favourite dragonfly is the twelve-spotted dragonfly. The male is easy enough to identify with its twelve brown wing spots and eight white spots in between, but the female challenges us. She has the twelve brown wing spots, but only the faintest of white spots, sometimes no white spots at all. Without the white spots she looks a lot like the female common whitetail dragonfly. Just recently, we learned to pay attention to the lateral stripes on the female’s abdomen. On the twelve-spotted female, we can describe the markings as ‘lines’, but if we look closely, the lateral markings on the common whitetail resemble more a series of broken dashes, not merging with each other. The first photo below is the twelve-spotted dragonfly female; the second is the female common whitetail dragonfly.
We use lots of numbers to help us identify wildlife at the cottage, some in stripes, some in spots. We appreciate all the time and effort biologists have spent to name species, as it certainly makes it easier for us to be comfortable with some of our field identifications. This is the kind of mathematics we love.
For this article, we referred to our favourite entomology site www.bugguide.net, and Dennis Paulson’s Dragonflies and Damselflies of the East.