Red Admirals Returning
Our northern population of Red Admiral butterflies (Vanessa atalanta) migrates to southern states in the fall and over the winter a new generation of Red Admirals matures to fly north in early spring. They can be seen now feeding on dandelions and other early-blooming flowers as well as sap and bird droppings.
Adult Red Admirals live for about two weeks and during this time they mate and lay their green, hairy eggs on all species of nettle, where they are well camouflaged. Black, spiky larvae hatch and feed voraciously on nettle plants before pupating and emerging as vibrant orange-striped, white-spotted adult butterflies. There are two summer generations in the Northeast. Male Red Admirals are highly territorial, which is why they are commonly encountered chasing each other from their preferred roosting spots.
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Predator & Prey
Although insects are quickly disappearing, some remain active right up until hard frosts occur. These cold tolerant insects include an ambush bug which successfully caught a nectar-seeking butterfly on one of our warmer fall days.
As their name implies, ambush bugs ambush their prey by sitting motionless waiting for prey such as flies, small moths and butterflies, beetle larvae, and other true bugs to visit the plants they sit on. In this case, a Clouded (or possibly Orange) Sulphur butterfly failed to notice a Jagged Ambush Bug (Phymata sp.) which quickly grabbed its prey, delivered an injection of immobilizing and digestive fluid, and then drank the liquefying nutrients from the butterfly’s body. Ambush bugs have their mouthparts arranged into a single knife-like beak and as seen in this photograph, often capture insects much bigger than themselves.
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Monkey Slugs
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 often 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 are only about an inch in diameter. Adult moths bear a slight resemblance to bees and wasps.
What is unusual 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). The fact that it glides 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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Cecropia Moth Caterpillars Spinning Cocoons
As a larva/caterpillar the Cecropia Moth, one of our giant silk moths, usually has five larval stages, or instars, as it matures. At the end of the fourth instar the caterpillar begins spinning a silk cocoon within which it will overwinter as a pupa. The gland which produces the silk is located below the caterpillar’s mouth.
There are three layers to the cocoon: the outer layer (stiffened and waterproofed with a liquid secreted by the caterpillar), a middle insulating layer of very soft silk strands and the innermost layer which consists of a case that encloses the pupa.
After about ten days inside the cocoon it spins in August, the caterpillar sheds its skin one last time and emerges as a pupa. For the next ten months the pupa remains encased in the cocoon as it undergoes the transformation into an adult moth. The moth will emerge next June and live only about ten days, just long enough to reproduce. (FYI, the outer layer of the cocoon was constructed within 24 hours.)
(Thanks to Jim Canfield, discoverer of spinning Cecropia caterpillar; dissected cocoon was one in which the pupa never metamorphosed into an adult)
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2nd Brood of Black Swallowtails Emerging
The process of transforming from a caterpillar to a chrysalis is a miraculous one, but it’s especially intriguing when it comes to Black Swallowtails (Papilio polyxenes). For one thing, their chrysalises vary in color from green to brown, depending on the object on which they choose to attach themselves. Equally impressive, while it is still a caterpillar the Black Swallowtail spins a thread of silk from which it suspends itself. It uses this silk sling as support for the chrysalis that is revealed once the caterpillar splits and sheds its exoskeleton (see it dangling beneath the chrysalis).
The second brood of Black Swallowtails (Papilio polyxenes) is already emerging from their chrysalises this summer, mating and laying eggs during their two week adult life span. Look for the caterpillars dining on members of the Parsley family, including Queen Anne’s Lace, dill, parsley, fennel, celery and carrot foliage. (Photos from left to right: Black Swallowtail larva preparing to pupate, chrysalis (with cast off larval exoskeleton) and adult male Black Swallowtail)
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Cabbage Whites Mating
Cabbage White butterflies (Pieris rapae) are seemingly common, rather ordinary and unremarkable butterflies. That is, until you become acquainted more intimately with their reproductive idiosyncracies. The male’s sperm, along with a nutritious snack, is contained within a package called a spermatophore. It is the size of the spermatophore that defies belief, as it makes up 13 percent of the male’s body weight. Translated into human terms, a 150 male would possess a 20-pound package of sperm.
The male Cabbage White deposits its spermatophore into a pouch within the female’s reproductive tract and the sperm proceed to swim to a second pouch where they are used to fertilize the female’s eggs. The female absorbs the nutrients that accompanied the sperm and uses them to make approximately half the eggs she lays.
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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
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
The 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
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
Eastern 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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Abbott’s Sphinx Moth Larvae Maturing
The 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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First Brood of Pearl Crescents Emerging
The first of this summer’s broods of Pearl Crescents are maturing. Our smallest and most common black and orange butterfly can be found throughout the eastern half of the U.S.. This particular species is named after a crescent-shaped spot near the margin of the hind wing on the underside. Its wingspread is about an inch and a half. The exact pattern on its wings is highly variable, making it challenging at times to distinguish it from other crescents.
Asters are the primary food source of Pearl Crescent larvae. Mated females lay their clusters of 20-300 green-yellow eggs on aster leaves, and in roughly a week the brown, black and white spiny larvae emerge. Two broods are common in the Northeast, so one can continue to look for crescent caterpillars on asters into August. Note: The Northern Crescent is very similar-looking to the Pearl Crescent (it may not even be a distinct species). Photo could be of either species. All lepidopterists welcome to comment!
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Polyphemus Moth Cocoons
The 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
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
For 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
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
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
Luna 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
Poplar 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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Poplar Hawk-moths Emerging, Mating & Laying Eggs
June is well-known for the giant silk moths that emerge this month, but there are other large moths that are encountered as well, one of which is the Poplar Hawk-moth (Laothoe populi). Hawk-moths, also known as Hornworms (their larvae, which feed mainly on species of poplar, usually have a horn), are a type of Sphinx moth, which are known for their fast, enduring flight. One of the more familiar species of this family is the day-flying Hummingbird Hawk-moth, which can be seen hovering at flowers while sipping nectar with its proboscis.
Adult Poplar Hawk-moths, with wingspans as large as four inches, emerge in early summer. Their life is so short that they do not have a functional proboscis and do not eat, but concentrate on mating. Females extend a scent gland from the end of their abdomen to lure in the night flying males whose large claspers are frequently wide open as they fly in to lights around midnight. The moths mate and the females lay their pale green eggs on the leaves of poplars and willows, which the larvae eat once they hatch. Fully-grown caterpillars pupate and overwinter in shallow burrows in the ground.
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Mourning Cloaks Surviving On Sap
Who doesn’t celebrate at the sight of a Mourning Cloak butterfly gliding through the woods on soft, spring breezes? Because the adults spend the winter hibernating behind loose bark, Mourning Cloaks are among the first butterflies to take flight in the spring. Most butterflies overwinter as eggs or pupae inside chrysalises, and have to complete metamorphosis before they can take to the air.
Surviving in March and April, when there is little, if any, nectar to be found, is challenging. Mourning Cloaks sustain themselves with the sap that exudes from broken tree branches or wounds in tree trunks. Oaks are their preferred source of sap. When they find some, they walk down the trunk to the sap and feed head downward (see photo).
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