An online resource based on the award-winning nature guide


Blister Beetles’ Defense Mechanism

10-5 short-winged blister beetle 064Blister beetles are aptly named, for when they are disturbed they emit a yellow, oily, defensive secretion (cantharidin) from their joints which usually causes blisters when it comes in contact with skin. This toxin deters many potential predators and is especially effective against ants. According to naturalist/forester/writer Ginny Barlow, as little as 100 milligrams is reported to be fatal to humans if ingested, and this amount can be extracted from just a few beetles. Humans used to crush and dry blister beetles and use the resulting concoction for gout and arthritis. It was also used as a popular aphrodisiac known as Spanish fly. Because of its toxicity, it is no longer widely used in medicine.

Cantharidin is, however, indirectly used by tree-nesting nuthatches. With a limited number of tree cavities, there is competition among animals using them to raise their young, especially between squirrels and nuthatches. Nuthatches have been seen with Short-winged Blister Beetles (Meloe angusticollis, see photo) in their beaks, “sweeping” them on the bark around tree cavity entrances. The nuthatches don’t eat the beetles, they strictly use them as tools. It is assumed that the birds do this in order to repel squirrels with the cantharidin that is smeared on the tree. (Thanks to Ginny Barlow for photo opportunity.)

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Pigeon Tremex Horntails Laying Eggs

horntails 239Horntails, also known as wood wasps, are non-stinging, wood-eating insects that lay their eggs deep within trees. Both male and female horntails have a pointed spine at the tip of their abdomen; females also have a long, slender ovipositor. (They get their name not from their spine or ovipositor, but from a knob (cornus) at the tip of their abdomen.)

Pigeon Tremex Horntails (Tremex columba) are active in late summer and early fall. A mated female inserts her ovipositor several inches into a dead or dying tree and lays an egg (where it is safe from most, but not all, predators). Along with the egg the adult horntail deposits some white rot fungus (Daedalea unicolor) which she stores in special abdominal glands. The fungus breaks down and softens the wood for the horntail larva to eat and is required for the successful development of the horntail. The larva typically begins consuming the soft, fungus-ridden wood around it, and then chews its way to the inner bark so as to provide a means of exiting the tree when it becomes an adult. The larva then returns to feed on inner wood. It completes its metamorphosis and emerges from the tree within a year as a winged adult horntail.

There is a parasitic wasp, the Giant Ichneumon Wasp (Megarhyssa macrurus), which possesses a long three-inch ovipositor capable of drilling into trees. There are several theories as to how this parasitic wasp detects the presence of horntail larvae deep within the tree. She may lay her antennae on the outside of a tree and pick up the vibrations of horntail larvae gnawing away in their wood chambers. Another theory proposes that the female wasp uses her antennae to smell the frass (droppings) of the horntail larva as well as the wood-softening fungus. Once she locates a horntail larva, the ichneumon wasp paralyzes it and then lays an egg on it. The ichneumon wasp larva feeds on the paralyzed horntail larva, consuming it completely within a couple of weeks. The ichneumon wasp then pupates and remains dormant under the bark until the following summer, when the adult emerges.

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Yellow Jackets Rebuilding Nest

yellow jacket nest2From the size of the chunks of sod that were ripped out of the ground in order to access this subterranean yellow jacket (Vespula sp.) nest, one can deduce that a black bear, not a striped skunk or raccoon, was the nocturnal visitor. Usually there is little intact nest left after a bear tears it apart in an effort to find yellow jacket larvae, but in this case, a portion of the paper nest remained. Apparently undaunted, even with frost in the air (signaling the demise of all the yellow jackets except young, fertilized overwintering queens), the workers lost no time in rebuilding their nest. Twenty-four hours after their nest was torn apart, the colony of yellow jackets had diligently chewed enough wood fiber to have replaced much of it.

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Northern Tooth Fungus

9-22 northern tooth fungus 159Northern Tooth Fungus, Climacodon septentrionale, is an unusual combination of both a shelf (also called bracket) fungus as well as a toothed fungus. Typically a shelf fungus produces spores inside pores located on its underside. Northern Tooth Fungus, however, produces spores on pendant, spine- or tooth-like projections on its underside (see insert). This fungus usually has several tiers of “shelves” that grow in tight, thick layers, and change from white to light tan as they age.

Northern Tooth Fungus is a parasite of living trees, especially Sugar Maples, and it causes the central heartwood of the living tree to rot. The only sign that a maple has this fungal parasite is the appearance of these shelf-like fruiting bodies in late summer or fall. Often trees with this fungus become weak and are blown over by the wind. As with most shelf fungi, it is considered to be inedible. (Thanks to Jeannie Killam for photo op.)

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Snakeroot Flowering

9-17-15 snakeroot  261Snakeroot (Ageratina altissima) is a perennial with clusters of tiny flower heads each containing multiple white flowers at the tip of its stem. Its roots were used to make a poultice to treat snakebites, hence, its common name. Large patches of Snakeroot can be found flowering in Northeast woods at this time of year. Eventually tiny black seeds with white, hairy wisps are dispersed by the wind.

Snakeroot contains a toxin called tremetol that is toxic. An animal may die from eating either a large amount of Snakeroot at one time or small amounts over a long period. When the plant is consumed by cattle, the meat and milk become contaminated with the toxin. If this contaminated meat or milk is consumed, the poison is passed on, and if enough is ingested, it can cause “milk sickness” in humans, a potentially lethal illness. Thousands of mid-West settlers in the early 1800’s died from this disease (possibly including Abraham Lincoln’s mother) as they were unfamiliar with the plant and its effect on their cattle. Snakeroot is also poisonous to horses, goats and sheep. Today small amounts are used by herbalists to treat a variety of ailments, from high blood pressure to insomnia. (Thanks to Jeannie Killam for photo op.)

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Bumblebees Raising Queens & Males

9-11-15  bumblebee emerging IMG_5476Unlike a hive of honeybees, where the queen and workers overwinter, the only bees in a bumblebee colony that live through the winter are young, fertilized queens. In early fall, bumblebees begin producing new queens as well as males in order to allow the colony to reproduce. Once the adult virgin queens and males have emerged from the silk cocoons within their pupal cells, they leave the hive. The male bees spend their time feeding on nectar and trying to mate with the new queens and the young queens mate with several males. Once fertilized, the queens continue to feed, building up fat bodies for the approaching winter. Once enough fat bodies are stored, queens begin searching for suitable overwintering locations. Overwintering sites are often in an abandoned chipmunk or mouse burrow, or in soft soil or compost, where they can survive temperatures down to – 5° F. due to a kind of “antifreeze” they produce. The rest of the hive (old queen, workers and any remaining males) dies once cold weather arrives. In the spring the queens emerge and start new colonies. (Thanks to Natalie Kerr & Sadie Brown for making this post possible and accurate.)

Photo by Sadie Brown: A recently-excavated underground colony of bumblebees (by a chemical-free “pest” controller) contained several wax pupal cells, as well as wet, silver-haired bumblebees (their color appears as they age) emerging from some of the cells. At this time of year, they are most likely to be queens or drones.

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Caddisflies Laying Eggs

9-3 caddisfly eggs & larvae 402Most caddisflies lay their eggs in or near ponds or streams. A very few species (in the family of northern case makers, Limnephilidae) deposit their eggs above the water on aquatic vegetation in a one- to-two-inch-long mass of jelly (some species’ eggs lack the jelly). Up to 800 eggs (the tan spots within the jelly in yesterday’s post) are laid at one time in one mass. Depending on the species, the eggs take from several weeks up to ten months to hatch. These masses are usually situated so that once the eggs hatch, the larvae will drop down into the water, where they will spend their larval and pupal stages.

Caddisflies are closely related to butterflies and moths, and one of the features they have in common is that the larvae have silk glands in their lower lip. Thanks to the ability to spin silk, the caddisfly larvae build portable cases or attached retreats out of natural material that is available. Some species build elongate tubes out of pieces of plants, sand, sticks or pebbles and reside in them while they drag them along with them wherever they go. Other species attach their cases with silk to crevices in or the bottom of stones in streams. Each species of caddisfly larva always constructs the same type of case, so that you can often tell the genus or even species of caddisfly by the appearance of its case.

The larval stage of a caddisfly can last two to three months or up to two years, depending on the species. Most species spend the winter as active larvae. When it is ready to pupate, the larva attaches its case with silk to something immoveable, such as a large rock. Inside its case, the larva spins a cocoon and eventually pupates inside of it. In two to three weeks the sharp-jawed pupa cuts its way out of its cocoon and floats up to the surface of the water where it emerges as a winged adult, often using its pupal skin as a raft for support during this process. Adult caddisflies live for about 30 days, during which time the males form mating swarms to attract females. After mating takes place, the egg-laying begins.

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