An online resource based on the award-winning nature guide

October

Keeping A Dead Leaf Partly Alive

If you look on the ground these days as yellow Trembling and Bigtooth Aspen leaves are falling, you may notice that small splotches of green remain in some of them.  These chlorophyll-laden patches are usually found near the bottom of the midrib of the leaf.  If you open the pocket of tissue at the base of the green section, it’s highly likely you will find a minuscule (2 mm long) translucent caterpillar (a microscope may be necessary to detect it).

The caterpillar (larva) first bores into the stem, or petiole, resulting in a swelling. When it reaches the leaf blade it makes an elongated blotch between the midrib and the first lateral vein. The larva is capable of secreting a chemical which prevents the natural deterioration of the leaf.  As a result, chlorophyll is retained in this area and photosynthesis continues to take place, providing the larva with food.  The leaf-mining larva (Ectoedemia sp.) will pupate over the winter (outside the leaf) and emerge next spring as a very tiny moth which will feed on the honeydew secreted by aphids. (Photo: Mined Bigtooth Aspen, Populus grandidentata, leaf)

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Green Stain Fungus Fruiting

Sac fungi, or ascomycetes, are a group of fungi most of which possess sacs, or asci, in which spores are produced. The relatively common blue-green cup fungi, Chlorociboria aeruginascens and its close relative, Chlorociboria aeruginosa, are in this group and are referred to as Green Stain Fungi (as well as Green Elfcup or Green Wood Cup). Most of the time you do not see the actual fruiting bodies of these fungi.  More often you come across the brilliantly blue-green stained wood (often rotting logs of poplar, aspen, ash and oak) for which these fungi are responsible. Woodworkers call this wood “green rot” or “green stain.” 14th and 15th century Italian Renaissance woodworkers used Chlorociboria-infected wood to provide the green colors in their intricate wood inlays. The blue-green discoloration is caused by the production of the pigment xylindein, which may make wood less appealing to termites and has been studied for its cancer-fighting properties.

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Yellowjacket Nests Being Raided

Because yellowjackets do not produce or store honey one might wonder why striped skunks, raccoons and black bears frequently dig up their underground nests.  It is the young yellowjackets (larvae), not honey, that is so highly prized by these insect-eating predators.  At this time of year it is crucial for them, especially black bears who go for months without eating or drinking during hibernation, to consume enough protein to survive the winter.

Whereas adult yellowjackets consume sugary sources of food such as fruit and nectar, larvae feed on insects, meat and fish masticated by the adult workers that feed them. This makes the larvae a highly desirable, protein-rich source of food. (Yellowjacket larvae reciprocate the favor of being fed by secreting a sugary material that the adults eat.)

Three to five thousand adult yellowjackets can inhabit a nest, along with ten to fifteen thousand larvae. Predators take advantage of this by raiding the nests before frost kills both the adults (except for fertilized young queens) and larvae in the fall.  Yellowjackets are most active during the day and return to their underground nest at night.  Thus, animals that raid them at night, such as raccoons, striped skunks and black bears, are usually very successful in obtaining a large meal.  Occasionally, as in this photo, the yellowjackets manage to drive off predators with their stings, leaving their nest intact, but more often than not the nest is destroyed and the inhabitants eaten.  (Thanks to Jody Crosby for photo op of yellowjacket nest (circled in red) dug up by a black bear – note size of rock unearthed.)

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Cottongrass

If you go to a bog at this time of year, you are apt to find a sea of white, cottony balls waving in the breezes.  These are the seed heads of Cottongrass (Eriophorum sp.), which are actually not grasses but sedges. (In contrast to grasses, which have hollow stems, the stems of most sedges are solid and triangular.) The similarity of these heads to cotton gave this plant its common name.

Cottongrass grows in acidic wetlands and bogs.  It tolerates cold weather well, and is found in the northern half of the U. S. as well as further north where it is food for migrating Caribou and Snow Geese on the tundra as well as Grizzly Bears and Ptarmigan.

The cottony seed plumes, which aid in the dispersal of Cottongrass seeds, are too short and brittle to be made into thread, but they have been used for pillow-stuffing, wound dressing and in the production of candle wicks and paper.

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Dust Baths

Some species of birds “bathe” in substances other than water. Often dust or sandy soil is the material of choice, but rotten wood and weed particles are also used.  Dust baths, also called dusting or sand bathing, are part of a bird’s preening and plumage maintenance that keeps feathers in good condition. The dust that is worked into the bird’s feathers while it kicks its feet and beats its wings in the sand will absorb excess oil to help keep the feathers from becoming greasy or matted. The oil-soaked dust is then shed easily as the bird fluffs its feathers and shakes itself vigorously. Usually some feathers come out as well, and it’s often possible to determine what species of bird has taken a bath by the feathers left behind. The pictured dust bath is sprinkled with Wild Turkey feathers.  Ornithologists feel that regular dusting may also help smother or minimize lice, feather mites, and other parasites.

Hundreds of bird species have been recorded as dusters.  Those that take regular dust baths include sparrows, pheasants, turkeys, thrushes, thrashers and wrens.  (Thanks to Jody Crosby for photo op.)

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Chlorophyll Breaking Down

It’s as if a magic brush painted the northern New England landscape with every conceivable shade of vibrant red, orange and yellow this past week.  The major player in this phenomenon is chlorophyll, the pigment that gives leaves their green coloration during spring and summer. Chlorophyll is able to absorb from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch, inside cell-like structures called chloroplasts, a process referred to as photosynthesis. But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. Chlorophyll breaks down and the green color of leaves disappears, revealing colors that have been masked by the chlorophyll all summer (as well as reds manufactured in the fall).  Imagine a world without chlorophyll, where the bright golds, purples, yellows, oranges and reds of autumn leaves would be the natural colors seen in spring, summer and fall.

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Wolf’s Milk Slime Mold Fruiting

If you examine rotting logs after a rain between the months of June and November, it’s likely you eventually will find what looks like a cluster of tiny (under ¾”), pinkish puffballs growing out of the surface of one or more logs.  Although these growths resemble fungi and were at one time classified as such, they are now classified as slime molds, some of the world’s strangest organisms.  Long mistaken for fungi, slime molds are now classified as a type of amoeba.

The name of these pink balls is Wolf’s Milk Slime Mold, or Toothpaste Slime (Lycogala epipendrum).   They are one of the most frequently noticed slime molds in North America, probably due to the bright color of the young fruiting bodies (aethalia).  The common names derive from the paste-like pink substance found inside of them.  As the fruiting bodies age, both their exterior and interior turn purplish, then gray or brown (see photo inset). At maturity the paste develops into powdery grey spores.

When not fruiting, single celled individuals move about as very small, red amoeba-like organisms called plasmodia.  When certain conditions change, the plasmodia convert into the pinkish, spore-bearing structures seen this this photograph.

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