The Polyphemus Moth is a giant silk moth, a member of the Saturniidae family which includes some of the largest species of moths. Giant silk moths derive their name from both their size as well as the fine silk they use to spin the cocoons which serve as protection for the pupal stage in their life cycle.
Most Polyphemus Moth cocoons start out attached to a tree branch, although some are spun among leaves or grasses on the ground (see pictured cocoon). They are oval, roughly 1 ½” long and nearly an inch wide. Cocoons in trees are susceptible to attack by squirrels and woodpeckers, whereas mice are the biggest threat to cocoons on the ground.
The moth overwinters as a pupa inside the cocoon. Unlike most other giant silk moths’ cocoons, the Polyphemus Moth cocoon lacks an escape “valve” at one end. In order to emerge (as an adult) from the cocoon the summer after it spins it, the moth secretes an enzyme that digests and softens the silk at one end. Then it moves about the cocoon in a circular pattern, tearing the softened silk with two spurs located at the base of each wing on its abdomen. Eventually it escapes by splitting the silk and pushing the top up.
Only Naturally Curious readers would come up with flossing!
If lemmings are in short supply and you’re a Snowy Owl, head for tall grass where small rodents dwell. This juvenile female Snowy Owl successfully caught a Meadow Vole (along with a footful of grass) in its talons and proceeded to swallow the vole whole, along with some of the grass. However, most of the grass remained hanging from the owl’s mouth after the vole had been consumed, so it proceeded to grasp the grass with its foot and pull it out of its mouth (yesterday’s Mystery Photo).
Although many people are under the impression that hard weather forces Snowy Owls farther south some winters, the reason for Snowy Owl invasions or irruptions turns out to be linked to either prey population crashes in the north, high productivity breeding years (producing more predators than the prey can support) or a combination of the two. New research has shown that the abundance of Snowy Owls seen in the eastern U.S. during the winter of 2013-14 was the result of a particularly good nesting season on the Arctic tundra. A population boom of lemmings, the Snowy Owl’s primary food source, translated to a population boom of owls.
Snowy Owls have begun appearing in New England in search of food, giving us the relatively rare opportunity to observe their natural behavior. Do you know what this Snowy Owl is doing? Please click on “Comments” underneath this post on my blog to respond.
Milkweed, a perennial plant that can adapt to adverse soil conditions, has recently been recognized as a viable source of fiber for fill for jackets and comforters. Winter coats insulated with a compressed layer of milkweed fluff are have been shown to be as effective at retaining body heat as those filled with down or polyester, and a Canadian company is now manufacturing and selling them.
Although historically considered a “weed,” milkweed came into its own during World War II, when overseas supplies of the insulating fiber from the kapok tree were cut off and milkweed fluff was harvested for use in life jackets. The U.S. government launched a program that enlisted the help of children: if they could fill up a large onion bag of milkweed fluff, they would receive fifteen cents. This incentive proved very popular, and the U.S. was able to stuff over 1.2 million life vests with milkweed fluff. However, after the war, the rising use of synthetics lessened interest in all natural fibers, and milkweed went back to being considered a less than desirable weed.
Recently milkweed populations have been declining, in part due to herbicides and loss of habitat. However, with the growing interest in this plant as a source of commercial fiber it is now being planted as an agricultural crop, with some Vermont and Canadian farmers devoting acres of farmland to its growth. This, of course, is a boon to monarchs, as milkweed leaves are the sole source of food for monarch larvae. Not only is milkweed being cultivated, but the farmers growing it are making an effort not to harvest the plants until monarchs have migrated in the fall. A win-win situation for all concerned.
Opportunities to see turtles in winter are extremely limited, but a hole chopped in pond ice recently revealed a Snapping Turtle swimming in the water beneath the ice. According to Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas(http://vtherpatlas.org/ ), most turtles don’t often burrow into the mud during winter. They need to take in dissolved oxygen from the water and there is not much available in the mud. Turtles take in oxygen through the linings of their mouths and sometimes thin-skinned, capillary-rich areas in their cloaca and armpits. Many turtles are just sitting on the bottom of ponds. They may use a rock, log, or maybe some leaves for a little protection from otters or other predators.
If the ice is clear, it is possible to see turtles swimming beneath it. Andrews suggests that the Snapping Turtle in the photograph is likely picking up an oxygen boost by using its lungs for a change. It may be four more months before it gets another breath of fresh air. (Thanks to Jim Andrews for post and Barb and Paul Kivlin of Shoreham, VT for photo.)
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Naturally Curious posts will resume on December 28th!