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Lepidoptera

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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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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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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A Butterfly’s Proboscis May Act More Like A Paper Towel Than A Straw

9-24-18 sulphur butterfly IMG_9736The chewing mouthparts of a butterfly larva, or caterpillar, undergo changes when the larva develops into an adult butterfly. They are turned into a tube consisting of two parts, or galeae, that when joined form a structure called a proboscis. The proboscis looks like a straw, and has long been thought to act like one. It is often referred to as a sipping tool through which nectar is obtained by butterflies. However, recent discoveries have scientists thinking that the proboscis works more like a paper towel than a straw.

The liquid that a butterfly feeds on in addition to nectar – animal tears, juice inside decomposed fruit, tree sap, sweat, liquid contained in scat – is so viscous that sipping or pumping it through the proboscis, or feeding tube, would require an enormous amount of pressure. It’s been suggested by entomologist Konstantin Kornev of Clemson University that butterflies draw liquid upwards using capillary action – the same force that pulls liquid into a paper towel. The proboscis actually resembles a rolled-up paper towel, with tiny grooves that pull the liquid upwards along the edges, carrying along the bead of liquid in the middle of the tube. (Photo: Sulphur Butterfly on New England Aster)

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Viceroys — Master Mimics

8-17-18 viceroy metamorphosis

A plump caterpillar is irresistible to many insect-eating birds, and some of them (notably Viceroys and Giant Swallowtails) have outfoxed their predators by assuming the appearance of bird droppings, which one assumes is a far less appealing meal.  They do this using color, pattern, choice of resting place and even position – contorting their bodies to match the shape of bird droppings. The Viceroy (Limenitis archippus) uses this technique during its later larval and pupal stages.

The adult Viceroy butterfly also uses mimicry to enhance its survival, but it mimics another butterfly — the Monarch — not bird droppings.  Both the Viceroy and the Monarch are unpalatable and contribute to each other’s protection from birds with this strategy, a relationship known as Mullerian mimicry.

In New England there can be up to three broods of Viceroys, with the larvae of some of the second brood and all of the third brood overwintering and pupating in the spring.

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Eastern Black Swallowtails Laying Eggs

7-23-18 black swallowtail female laying eggs_U1A2171Eastern Black Swallowtail (Papilio polyxenes) butterflies are mating and laying eggs.  The female Eastern Black Swallowtail can appear quite frantic as she visits multiple host plants just long enough to leave a very tiny, spherical, pale yellow egg before heading on to the next plant.  In the wild, Queen Anne’s Lace, Wild Parsnip, Golden Alexander and Poison Hemlock are favorite host plants; in vegetable gardens you frequently find larvae (if you should miss the eggs) on dill, fennel and parsley.  Entomologists have found that host plant odor is one of the cues involved in the Eastern Black Swallowtail’s choice of where to lay eggs.

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