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Moths

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

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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

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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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Fall Webworms

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For several weeks white webs on the tips of branches have been apparent on many trees.  These silken tents are the work of the Fall Webworm (Hyphantria cunea), a moth most associated with its larval stage. Fall Webworm caterpillars construct a web over the end of a branch, enclosing leaves on which they feed.  As the hairy, white caterpillars grow, they enlarge the web to encompass more leaves, with tents sometimes extending two to three feet.

Often mistaken as the work of Eastern Tent Caterpillars, the tents of these two moths can be distinguished by the season they appear (ETC are active in the spring, Fall Webworms in the fall) as well as the location of the tents (ETC are usually in the crotches of trees, Fall Webworms at the tip of branches). As soon as the eggs hatch in early summer, the Fall Webworm larvae begin to spin small silk webs over the foliage of the deciduous trees on which they feed (over 90 species). By fall the tents are conspicuous. A look inside one  reveals caterpillars, dead partially-eaten leaves, and fecal droppings.

The larvae feed together inside the increasingly large web for roughly six weeks, at which point they often start feeding independently before pupating in the ground over the winter and emerging as adult white moths the following summer.

If your favorite tree has one or more Fall Webworm nests in it, there’s no cause for alarm. These caterpillars may defoliate a tree occasionally, but rarely kill it, and usually only build tents on a handful of branches, if that. The larvae have more than 50 natural predators and 36 parasites that help control them. Also bear in mind that Fall Webworms do not eat the buds of next year’s leaves and the leaves they are feeding on will soon to drop to the ground. Next year leaves will appear on the currently affected branches with no sign of last year’s damage.

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Second Brood of Snowberry Clearwing Moths In Flight

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Clearwing moths are strong and fast fliers with a rapid wingbeat, like the other members of the Sphingidae family. Most species in the group are active at dusk and feed much like hummingbirds, hovering in front of a flower and sipping nectar through their extended proboscis.  In most species, the larval stage is called a “hornworm” because the caterpillar’s posterior end has a horn-like appendage protruding upward.

Like its close relative, the Hummingbird Clearwing (Hemaris thysbe), the Snowberry Clearwing (Hemaris diffinis) is a day-flying moth, has transparent wings and is a mimic.  While they both hover at flowers, the Hummingbird Clearwing is said to mimic a hummingbird, while the Snowberry Clearwing is considered a bumblebee mimic.  To distinguish these two clearwings, if it has black legs and a black band that crosses the eye and travels down the side of the thorax, it’s a Snowberry Clearwing.

In addition to thistle, adult Snowberry Clearwings feed on honeysuckles, snowberry, hawkweed, lilacs and Canada violets. (Thanks to Barbara and Knox Johnson for photo op.)

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Abbott’s Sphinx Moth Larvae Maturing

7-23-18 Abbott's sphinx moth_U1A2632The larvae of sphinx moths, commonly called hawk or hummingbird moths, are easily recognized by the horn, eye spot or hardened button that is near the tip of their abdomen.  Most readers are probably familiar with the larval stage of tobacco and tomato hornworms (Carolina Sphinx Moth and Five-spotted Hawk Moth, respectively) which are found on tomato plants. A less observed sphinx moth, Abbott’s Sphinx Moth (Sphecodina abbottii), can be found on grape and Virginia creeper vines.  As a larva it molts several times and assumes three different appearances by the time it pupates.

Abbott Sphinx Moth larvae start out green, with a horn near the tip of their abdomen, like most other sphinx moths. However, when they are about half-grown, they turn blue-green and the horn develops into an orange knob (see inset).  In the last stages before they pupate, the larvae molt and the knob turns into an “eye,” complete with a black pupil and encircling iris.  The finishing touch is a white reflection spot that makes the eye appear moist and shiny.  At this point, the larvae may be either brown with a “wood-grain” pattern (resembling grape vines, a host plant) or brown with ten pale green saddles along the back (thought to resemble grapes).  Pictured are the second and third stages of a brown “wood-grain” Abbot’s Sphinx Moth larva.

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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.