(This 791st Buffalo Sunday News column was first published on May 28, 2006.)
The brown case that hung from a dogwood twig all winter looks a bit like a milkweed pod, but this container doesn't hold a milkweed's feathery parachutes. Instead it holds a slowly pupating insect.
This cocoon has protected a life within from the winter's subfreezing temperatures and the inches deep snow piled on it, but now after several warm and humid nights in late May it is torn open from within. Slowly a large body emerges and equally slowly expands its collapsed form like one of those automatically extending tents, finally to display a beautiful female cecropia moth, the largest moth of our woodlands.
Photo by David W. Walsh
Its attractive brown and gray colored wings are almost six inches wide; its body is thick, hairy and strikingly marked with reddish-brown and white stripes; its large antennas are like delicate many-tined combs. Like many moths its wings have eyespots that some naturalists believe are there to make the insect appear like the head of a larger animal and thus to scare away predators.
But this lovely insect has no time to admire itself. It has only about two weeks to complete its life cycle. It will not even eat during this period.
Now it emits a chemical signal, a kind of perfume technically called a pheromone. These complex molecules drift through the air until after a time, a few hours or even several days, they reach a male cecropia. The male looks much like the female but its antennas are even larger and more delicate for they must pick up the few molecules of this signal that reach it.
A few of these pheremones reach a moth almost a mile away and this eager suitor instinctively knows just what to do. Immediately he flies upwind to seek out this mate.
Despite its long flight it is the first of its kind to reach this female and they immediately copulate, remaining attached for nearly a full day.
The male's duties are now fulfilled but the female must perform one more act before it too will die. It carries forward the life of the species by laying about a hundred tiny, newly fertilized eggs. She attaches these eggs in small groups to leaves or twigs of one or more of its favorite plant species: apple, alder, birch, box elder, cherry, dogwood, pear, plum or sugar maple.
Many of those eggs are found and eaten by eager chickadees, nuthatches, creepers and gnatcatchers, but a few dozen remain hidden for almost two weeks. Then they are chewed open from within to allow tiny black caterpillars, only the size of mosquitoes, to emerge and begin to eat the leaves around them.
These too are preyed upon not only by birds but also by other insects including a tiny spider.
These caterpillars grow fast and pass through several stages called instars, changing color as they do until the few remaining finally end up in late August huge green caterpillars, five inches long. Although these are scary looking tank-like insects topped with bristly horns, some brightly colored yellow, red and even blue, they too make juicy meals for their many enemies.
Photo by Jim Kalisch
Still a few of those hundred hatchlings do reach that final stage of that part of their lives. They find an appropriate twig and spin the cocoon in which they will metamorphose over the winter into another generation of beautiful cecropia moths.-- Gerry Rising