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Moths

Polyphemus Moth Cocoon

Congratulations to Stein, the first person to correctly identify Monday’s Mystery Photo as the cocoon of a Polyphemus Moth!

The Polyphemus Moth is one of our giant silk moths, spinners of the largest cocoons in North America.  Leaves are often woven into the surface of the cocoon in which the Polyphemus pupa spends the winter.  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.

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American Dagger Moth Caterpillars Roaming

American Dagger Moth (Acronicta americana) caterpillars are present from June to October in the Northeast, but because of their size (up to 2 ½”) and their searching for a suitable site to pupate in over the winter, they are very evident right now.

American Dagger Moth caterpillars have lemon yellow (early instars) or white (late instars) setae, or hairs.  Their distinctive characteristic is the pattern of black tufts: two pairs of diverging tufts along the middle of the caterpillar and one thick black tuft at the end. As larvae they have a wide variety of host trees, including alders, ashes, birches, elms, hickories, maples, oaks, poplars, walnuts, and willows.

After locating a wintering site, these caterpillars will spin a cocoon in which they will spend the next several months as pupae.  Late next spring American Dagger Moths will emerge from their cocoons as two-inch-long brown moths.

If touched, these caterpillars can cause a mild allergic reaction (a rash) in some people who touch the them.

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Monkey Slug Season

Congratulations to Rinky Black, who was the first person to accurately identify the Mystery Photo as a Monkey Slug!

Some of our dullest-looking moths started their lives out as colorful, bizarrely-shaped caterpillars.  In particular, there is a family of caterpillars (Limacodidae) known as “slug caterpillars” which come in all kinds of unusual forms and colors.  They can be naked or densely hairy, and they usually have stinging hairs. The Hag Moth (Phobetron pithecium), found throughout eastern North America, is one such moth. Whereas the adult moth is a dull brown, the caterpillar stage is anything but dull.  Known as the Monkey Slug, the caterpillar stage of this moth has three pairs of long “arms” and three additional pairs about half as long.  Its appearance has been likened to a tarantula (many of our insectivorous birds winter in the tropics, where there are tarantulas (which the birds avoid), and therein lies the reason for the caterpillar to look like one).  Although most photographs make Monkey Slugs look large, they measure only about an inch in diameter. Adult moths bear a slight resemblance to bees and wasps.

What is eye-catching about Monkey Slugs (as well as other slug caterpillars), besides their bizarre appearance, is the way in which they move.  Monkey Slugs glide – instead of the typical prolegs (located behind six true legs) they have suckers (see bottom right inset).  This gliding is responsible for its being classified as a “slug” caterpillar, for it moves much like a slug does.  The Monkey Slug is one of the slug caterpillars that does not sting, so you can handle it safely should you find one. (Thanks to Kathy and Geoff Marchant for photo op.)

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Snowberry Clearwing Moths Gathering Nectar

There are four species of clearwing (also referred to as hummingbird) moths in North America. The most familiar ones are the Snowberry Clearwing (Hemaris diffinis) and the Hummingbird Clearwing (Hemaris thysbe).  These day-flying moths fly and move like hummingbirds (hovering near flowers while drinking nectar) and the males have a flared “tail” like that of a hovering hummingbird.  It is also very easy to mistake one for a bumble bee.  Scales cover the wings of butterflies and moths, but clearwing moths lose many of these scales and thus have partially transparent (“clear”) wings.

Like most moths, clearwing moths have a very long tongue (can be twice as long as their body) which they carry rolled under their heads and that they use to reach the nectar of long-necked flowers.  They are attracted to the flowers of phlox, beebalm, honeysuckle and swamp milkweed (pictured), among others. If you approach a clearwing moth as it hovers, you may detect the humming sound that they make with their wings.

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Great Ash Sphinx Moth

Sphinx moths are notable for their fast flight and rapid wingbeat.  These attributes account for one of their common names — “hawk” moth. Most species of sphinx moths are capable of hovering in front of the flower from which they are drinking nectar, and some species are referred to as “hummingbird” moths.

In their larval form, sphinx moths are notable for the horn which extends upward near the end of their abdomen.  Tomato growers are familiar with the Tobacco Hornworm (Tobacco Hawk Moth/Carolina Sphinx Moth) and Tomato Hornworm (Five-spotted Hawk Moth).

Less frequently encountered is the larva of the Great Ash Moth (Sphinx chersis). Named for a host plant of the adult moth, this greenish or pinkish caterpillar has seven long diagonal lines along its body, which are sometimes edged with pink. Its black spiracles (external openings that allow gas exchange) are elongate and ringed with white. Its horn is blue or pink.  As an adult moth, it is gray with black markings and has a wingspan of up to five inches. You’re most likely to see this moth at dusk, feeding at deep-throated flowers. (Thanks to Heidi Marcotte and Tom Wetmore for photo op.)

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Promethea Moth Cocoons

11-28-18 promethea moth cocoon_U1A2802

At this time of year, most deciduous trees have lost their leaves. Bare branches make looking for cocoons and finding them much easier. A single leaf dangling from an otherwise barren branch of a tree might very well turn out to be the winter domicile of a Promethea Moth (Callosamia promethea) pupa.

These giant silk moths construct their protective two-inch-long silken cocoons while still in their larval/caterpillar stage.  First silk is spun around the stem of the leaf (petiole) as well as where the petiole attaches to the branch, in order to reinforce the attachment of the leaf to the tree.  The cocoon is then spun, with the leaf serving as its outer covering. The result is a perfectly disguised shelter that looks like a dead leaf hanging from a branch.

The caterpillar pupates after completing the cocoon.  After spending the winter in the pupal stage, the adult moth will emerge in early summer through a valve-like opening at the upper end of the cocoon.

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Woolly Bears Seeking Hibernacula

10-10-18 isabella tiger moth 119

The Isabella Tiger Moth typically has two broods during the summer.  The caterpillars (Woolly Bears) in the first brood pupate and emerge as adult moths mid-summer.  The second brood overwinters as caterpillars and pupate in the spring.  The Woolly Bears we see crossing roads at this time of year are second-brood caterpillars in search of protective hibernation sites (hibernacula).

Old-timers predicted the severity of the coming winter by the relative lengths of the black and brown bands of the caterpillars when they became easy to observe in the fall – the longer the black sections and narrower the brown section, the harder a winter they were in for.  In fact, this may have had some validity, as brown hairs (setae) are added to the middle band every time the caterpillar molts. Therefore, the older the caterpillar, the wider the brown band.  If winter comes early, the caterpillar’s brown band would be relatively narrow due to the fact it didn’t have time to mature fully and develop a wider brown section before hibernating.

The adult stage of the Isabella Tiger Moth is often overlooked, due to the appeal of the larval stage.  This tan moth, with a wingspan of 1 ½ – 2 inches, has tiny black markings on its wings.  Male and female are sexually dimorphic and can be distinguished by the color of their hind wings.  Males have yellow-pale orange hind wings while the hind wings of females are rosy. (Photo:  Woolly Bear; photo inset: female Isabella Tiger Moth)

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