The larvae of moths and butterflies are very susceptible to predation, especially by birds, and they utilize many different strategies to protect themselves. Shapes, colors and behavior all contribute to their survival. Some larvae take on the appearance of less appetizing things, such as bird droppings, twigs or leaves. Some have large eye spots which presumably scare predators. Others have cryptic coloration which makes them all but invisible. The pictured green caterpillar uses both color and behavior to visually disappear on the fern it is consuming.
These mating Pearl Crescent butterflies may have used size, color, shape, vein structure and/or pheromones to recognize each other. When mating, most male butterflies provide a package (spermatophore) of sperm and nutrients the female needs to produce and lay eggs. The mated female stores the spermatophore in a sac called a bursa until she’s ready to lay eggs. She fertilizes her eggs as she lays them, using the last sperm she received first. For this reason, males of some species will leave a substance that dries into a film on the female’s abdomen in an effort to keep her from mating with other males. (Thanks to Kent McFarland for butterfly i.d.)
The relationship between beavers and waterfowl is a strong one. In creating ponds and wetlands, beavers provide valuable waterfowl habitat. Beaver ponds are attractive to most dabbling duck species, particularly American Black Ducks and Mallards (pictured). Dead snags that are often found in beaver ponds provide Hooded Mergansers, Common Goldeneyes, Buffleheads and Wood Ducks with nesting cavities. During spring and fall, beaver ponds are used by migrating waterfowl, such as Green-winged Teal and Ring-necked Ducks, for the fuel they provide (aquatic invertebrates, plant seeds, tubers, buds and rhizomes). Waterfowl surveys in 2002 in Wyoming found that rivers and ponds with beavers had 75 times more ducks than those without beavers.
The chipping of hungry Hairy Woodpecker nestlings can easily be detected by human ears, even though it comes from deep within a tree cavity. One is reminded of how beneficial this species is when observing the steady delivery of food by these woodpeckers to their young. More than 75% of an adult Hairy Woodpecker’s diet consists of injurious insects, while the amount of useful insects and cultivated fruits that they destroy is insignificant. Beetle larvae (mostly wood-boring) make up 30% of the insects that are consumed, with ants ranking second, at 17%. Caterpillars, such as those pictured, comprise about 10% of an adult Hairy Woodpecker’s diet, but given this parent’s beakful, one wonders if the percentage is greater for nestlings.
Butterflies in the family Nymphalidae are also referred to as brush-footed butterflies (their front pair of legs are much reduced, brush-like and nonfunctional). Several species of Admiral butterflies belong to this family, and one of the most common in New England is the White Admiral, also known as the Red-spotted Purple. White Admirals overwinter as caterpillars and emerge in late April to feed for several weeks on the young leaves of cherries, willows, poplars and birches, as well as other trees, before forming chrysalises and transforming into butterflies. It is relatively easy to recognize the larva of any species of Admiral butterfly, as they are our only horned bird-dropping mimics. Quite an effective way to discourage predators!
Tiger beetles (named for their ferocity) can be easily recognized by their quick, jerky movements, huge eyes and large, multiple mandibles. Look for these voracious hunters in sunny, open spots where they can easily spot prey and potential predators. The six-spotted tiger beetle is hard to miss, thanks to its iridescent green outer wings, or elytra. Contrary to that which its name implies, this species can have five, two or even no white spots. It is most likely to be found on exposed rocks, logs and tree trunks, whereas the twelve-spotted (may have 12 or fewer spots) tiger beetle tends to prefer moist sandy spots. They both capture and liquefy their prey by masticating it with their formidable mandibles, squeezing it and swallowing the juice. Both of these species of tiger beetles have a two year life cycle, overwintering as adults their first winter, emerging early in the spring, mating and laying eggs during the summer and then overwintering as larvae.
In the fall and winter, fruit makes up about 90% of an American robin’s diet. In the spring, only 10% of a robin’s diet consists of fruit; invertebrates make up the remaining 90%. (Summer is a fairly even mixture of both.) At this time of year, earthworms are a popular food item with robins. Watching a robin foraging for a worm can make you wonder whether the robin is using its ears or its eyes to locate the worm. It turns out that most worms are seen, not heard, by robins. Because the sound of worms burrowing in the soil is of low intensity, they usually cannot be heard by robins because of background noise. Using sight, not sound, the robin first aims one eye toward a spot on the ground in front of it, and after holding this position for a few seconds, rotates its head and draws a bead with its other eye on the same spot– an earthworm in its burrow. The robin then quickly thrusts its bill into the burrow in an attempt to get its next meal.
It’s always surprising to find any form of life crawling on top of the snow, but for some reason spiders seem particularly fragile and susceptible to the elements. There are species, however, that remain active in winter, even in the northeast. Most live in the leaf litter beneath the snow, but they often emerge when temperatures are about 25°F to 35°F. Tentative I.D. has the spider in the photograph belonging to the genus Tetragnatha.
A pileated woodpecker’s diet often shifts with the seasons. One study found that the primary food of these woodpeckers was fruit in fall, carpenter ants in winter, wood-boring beetle larvae in early spring, and a variety of insects in summer. During the winter, with the help of its impressive beak, the woodpecker pries off long slivers of wood from trees containing carpenter ants and exposes the ant galleries. It then uses its long, pointed, barbed tongue and its sticky saliva to catch and extract ants from the ant tunnels inside the tree. This winter diet can be confirmed by examining the contents of a pileated woodpecker’s droppings. Finding these droppings is simply a matter of locating a tree that has a considerable pile of wood chips at the base, indicating that a pileated woodpecker has spent a lot of time working on the tree – long enough to have deposited droppings in and amongst the chips. The droppings crumble easily and reveal a multitude of tiny, black, shiny carpenter ant body parts. (The whitewashed end is due to uric acid.)
The queen is the only wasp in a colony to live through the winter (the others all die), and she usually does so in a sheltered spot such as a rotting log or under the loose bark of a tree (pictured). I wasn’t aware, until discovering this wasp, that queens actually chew a cavity in which to hibernate, but that appears to be the case in some instances. You can see the woody bits of fiber under the wasp that accumulated from her excavating the chamber. The cavity is roughly one inch long and ¼-inch deep. As a rule, hibernating queen wasps protect their wings and antennae by tucking them under their bodies. Some species produce glycerol, which acts as an antifreeze, while others allow ice to form around their cell walls and simply freeze solid. Most queen wasps die over the winter, primarily from predation by other insects and spiders, not the cold. (The pictured wasp had succumbed.) Warm winters are more likely to affect queens, as they emerge from hibernation too soon and starve due to lack of food.
There is no mistaking what bird is responsible for the large holes that a pileated woodpecker makes in an attempt to gain access to the carpenter ants living within a tree. No other bird in North America is capable of excavating holes of this size. Pileated woodpeckers tend to work vertically, and you often find one hole drilled above another. A look inside these holes reveals the galleries that the ants create in order to travel to all parts of their nest located within the dead center of the tree. (Carpenter ants, while omnivorous, do not consume or digest wood; they merely tunnel through it.) A tree’s inner core provides structural support, but is not essential for the tree’s survival. This eastern hemlock’s cambium layer, just inside the bark, is very much alive and the tree may continue to live long after its center becomes hollow.
In December, in Vermont, you don’t expect to come across an active spider, but yesterday that’s exactly what happened. A Green Long-jawed Orbweaver (Tetragnatha viridis) was crawling on the duff underneath a stand of hemlocks. Upon noticing me, this slender ¼” spider immediately formed itself into a straight line, with four of its legs stretched forward, and four backwards. Assuming this shape enables these spiders to be very well camouflaged on a blade of grass. There are 25 species in this genus in North America, all of which are called “stretch” spiders, referring to their elongated body form. They are very agile and can navigate on the surface of water very well.
If you’ve walked in New England woods recently, chances are great that you’ve noticed light tan moths with a one-inch wing span flitting about — an odd sight for this late in the year. These are male Bruce Spanworm Moths (Operophtera bruceata), also called Winter Moths, as the adults are active from October to December. They belong to the Geometer family of moths, the second largest family of moths in North America, which includes many agricultural and forest pests. The males are seeking wingless, and therefore flightless, females to mate with. Eggs are laid in the fall, hatch in the spring, the larvae pupate in the summer, and emerge as adult moths in the fall. Bruce Spanworm larvae periodically defoliate hardwood trees, preferring the buds and leaves of sugar maple, American beech and trembling aspen trees.
Meadowhawks are the only small red dragonflies seen in New England (most males are red, most females are brown).The latest species of dragonfly flying in the fall in this area is the Autumn Meadowhawk (Sympetrum vicinum), which doesn’t emerge until mid-summer. It seems a bit incongruous to observe these dragonflies not only flying, but mating and laying eggs in late October, but that is exactly when you can expect to see them. Until there have been several hard frosts, these winged masters of the air are able to keep active by basking in the sun and warming their flight muscles. The two pictured Autumn Meadowhawks are copulating in the typical “mating wheel” fashion, with the male grasping the female behind her head while the female places the tip of her abdomen at the spot on his abdomen (the seminal vesicle) where he stores his sperm. The female Autumn Meadowhawk lays her eggs in tandem with the male (his presence prevents other male meadowhawks from replacing his sperm with their own).
What happens to insects this time of year? A few remain active, such as snow fleas, and some, like monarch butterflies, migrate, but the vast majority of insects overwinter in New England. The insects that stay here are susceptible to freezing due to the fact that they cannot control the temperature of their body. Some insects, such as woolly bear caterpillars, can tolerate having ice form in their tissues, but most insects go into a state known as diapause. When the days start getting shorter, these insects reduce the water content of their body, as water freezes at a high temperature compared to other liquids, and replace it with glycerol, which acts like antifreeze, protecting them from freezing. (Please excuse duplicate post. I’m testing new posting process.)
What happens to insects this time of year? A few remain active, such as snow fleas, and some, like monarch butterflies, migrate, but the vast majority of insects overwinter in New England. The insects that stay here are susceptible to freezing due to the fact that they cannot control the temperature of their body. Some insects, such as woolly bear caterpillars, can tolerate having ice form in their tissues, but most insects go into a state known as diapause. When the days start getting shorter, these insects reduce the water content of their body, as water freezes at a high temperature compared to other liquids, and replace it with glycerol, which acts like antifreeze, protecting them from freezing. (Due to technical problems which hopefully will be resolved soon, I am unable to include a photograph with this post. My sincere apologies.)