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Polyphemus Moth Cocoons

12-15-17 polyphemus cocoon2 IMG_4455The 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.


Bruce Spanworm Moths Emerging

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If you’ve walked in northern New England woods recently, chances are great that you’ve noticed light tan moths with a one-inch wing span flitting about — with temperatures in the 20’s, this seems slightly incongruous. However, there are some insects that are active in cool weather, among them the Bruce Spanworm Moth (Operophtera bruceata), also called Winter Moth and Hunter Moth (these moths are active during deer hunting season, which approaches winter). The adults of this species are active from October to December.

Bruce Spanworm Moths belong to the Geometer family, the second largest family of moths in North America. All the flying moths you see are males seeking wingless, and therefore flightless, females to mate with. The females crawl up the trunk or branch of a tree and send out pheromones to attract winged males. After mating, the female lays her eggs which hatch in the spring. Larvae pupate in the summer and adult moths emerge in the fall.

Many Geometers are considered agricultural and forest pests. Bruce Spanworm larvae periodically defoliate hardwood trees, preferring the buds and leaves of Sugar Maple, American Beech and Trembling Aspen trees. In 1958 in Alberta, Canada, at the peak of a 10-year infestation, over 50,000 acres were moderately or heavily affected by Bruce Spanworm larvae.

Painted Ladies On Their Way

9-28-17 painted lady2 IMG_1979For the past few weeks we have been witnessing the migration of thousands of southward-bound orange butterflies, a vast majority of which are not Monarchs (although they are having a good year, too) but Painted Ladies (Vanessa cardui). Both their large numbers and the length of time that they have lingered in the Northeast this fall are unusual.

This was a good year for Painted Ladies — they migrated north earlier than usual, arriving in mid-April, possibly giving them time to have an extra generation, reproducing twice instead of once during the summer. In addition, the unusual weather we’ve been having has not been great for migrating. The butterflies have spent a lot of time fueling up on nectar while waiting for a wind out of the Northeast to assist them in their flight to the Southwest. With the prevailing wind change we’re now experiencing, it’s likely many of them will resume their migration today.

Geometrid Larvae Dangling

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The larvae of moths in the family Geometridae (the second largest family of moths in North America) are known as loopers, inchworms and spanworms. These names are derived from the looping gait of the caterpillars. They generally have only two or three pairs of prolegs (at the hind end) rather than the usual five pairs of most moth and butterfly larvae. The lack of prolegs in the middle of their body causes them to move by pulling the hind prolegs up to the true legs on the thorax in the front of their body, thereby forming a loop, and then extending the body forward.

Many Geometrid caterpillars evade predators by flinging themselves from trees and dangling by a silk thread that is attached to the tree at the other end (see photo). After the danger passes, they climb back up the silk and return to their leaf-eating.

Blinded Sphinx Moth vs. One-eyed Sphinx Moth

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Moths in the family Sphingidae are commonly called “hummingbird” (for their habit of hovering as they feed on nectar from flowers), “sphinx” (the larva holds its legs off the surface and tucks its head underneath, resembling the Egyptian Sphinx) or “hawk” (they fly with great speed and precision) moths.   Most are fairly large, with some species having a wingspread of up to 5” or more.

One group of sphinx moths is referred to as the “Eyed Sphinx Moths,” two of which are the Blinded Sphinx Moth (Paonias excaecata) and the One-eyed Sphinx Moth (Smerinthus cerisyi). The derivation of their respective common names can be easily ascertained by examining the upper surface of their hind wings. The Blinded Sphinx Moth has a single blue eyespot on each hindwing, whereas the One-eyed Sphinx Moth has a round or diamond-shaped black spot (“pupil”) in the center of each blue eyespot. The Blinded Sphinx Moth is light brown, whereas the One-eyed is a violet-gray. Both moths have scalloped wings that are held elevated and slightly away from the body. They are nocturnal, and regularly visit lights in small numbers. Their life is short, and adults of both species do not feed.

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Luna Moths’ Sonar Scramblers

6-26-17 luna moth 001Luna Moths, Actias luna, are known for their hindwings’ beautiful, long, green tails. These tails are not simply decorative, nor is their primary function to attract a mate (pheromones do that). A recent study found that Big Brown Bats have an easier time catching Luna Moths that have lost their tails. Further research revealed that Luna Moths defend themselves from voracious bats patrolling the night air by spinning the tips of their two wing tails in circles. The twisting tails of the moth act like a sonar shield, interfering with the bat’s means of locating them – echolocation. In contrast with the stronger, ever-changing echoes coming off of the moths’ large flapping wings, the twisted shape of the tails create a persistent weak echo signal. According to researchers, this could make the insects trickier to catch, and harder to track as they fly.

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Modest Sphinx Common & Scientific Name Correction

6-16-17 moest sphinx IMG_8668Poplar Hawk-moth and Big Poplar Sphinx are both common names used for more than one species of moth. Normally, the scientific name would clarify the identity of a species, but in yesterday’s post, the scientific name given was that of another moth with the same common name.

The confusion over the use of the same common names for different species of moths has led to the current use of the name Modest Sphinx for the moth depicted in yesterday’s post, with a scientific name of Pachysphinx modesta. It derived both common and scientific names from the fact that when it is seen up against a tree or other substrate with its forewings not fully extended, the bottom half of the moth is dark, as though “modestly covered” by a cloak or shawl. Thank you, Andree Sanborn, for your sharp eyes!

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