An online resource based on the award-winning nature guide


Large Yellow Underwing Larvae Crawling On Snow

12-12-16-large-yellow-underwing049a2252The striped caterpillar that is crawling along the surface of fresh snow is the larval stage of a noctuid or owlet moth known as the Large Yellow Underwing (Noctua pronuba). Noctuids are dull-colored, medium-sized, nocturnal moths that are attracted to lights in the summer. They usually possess a well-developed proboscis (mouthpart) for sucking nectar. The Large Yellow Underwing larva is one of many species  known as cutworms that feed on herbaceous plants. Introduced from Europe to Nova Scotia in 1979, this species has since spread north to the Arctic Ocean, west to the Pacific, and south to the Gulf of Mexico.

Larvae sporadically feed through the winter months whenever temperatures are above the mid-40s. The Large Yellow Underwing larva has been nicknamed the winter cutworm and the snow cut-worm for its ability to feed actively when other cutworms are dormant for the winter. Occasionally on warmer winter days, such as we had last week, you see them crawling on the snow.

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Milkweed Tussock Moths

9-6-16  milkweed tussock moth larvae 20160830_1764Milkweed Tussock Moth caterpillars are responsible for eating all portions of milkweed leaves but the largest veins that contain sticky latex. They can tolerate the cardiac glycosides within the milkweed plant that are toxic to most other insects as well as certain mammals and birds. Like Monarchs, these caterpillars retain the toxic compounds as adults, and are therefore avoided by many predators.

Female Milkweed Tussock Moths lay their eggs in masses on the underside of milkweed and dogbane leaves, which their larvae will eat. The hatching caterpillars are gray and hairy, but in no time they have developed the tufts of hairs that give them their name. When fairly young, the larvae tend to stay together, skeletonizing the leaves they consume. As they mature, the caterpillars tend to wander, and it’s unusual to find large groups of them on a single leaf.

Many of the insects that feed on milkweed have orange and black patterns as both larvae and adults. These colors serve as a warning to would-be predators. One of the adult Milkweed Tussock Moth’s main predators is bats. While the moth possesses these colors during its larval stage, as a pale brown adult (the stage that nocturnal bats prey on them) it lacks the bright coloration (which would provide little protection in the dark) but has an organ that emits an ultrasonic signal easily detected by bats. The signal warns that an attack will be rewarded with a toxic and distasteful meal, thereby deterring predation.

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Luna Moths Emerging

6-27-16  luna moth 002June is giant silk moth month, when these giant-bodied/winged moths in the family Saturniidae emerge.  Perhaps the most familiar giant silk moth is the Luna Moth, Actias luna. One of the largest moths in North America, its wingspan measures 4 ½ inches.  If you see one of these beautiful creatures, you are witness to its very short adult  lifespan.  After emerging from their cocoons, Luna Moths live for only about a week, during which time their sole mission is to mate. Like many other ephemeral insects, adult Luna Moths have no mouthparts and thus, do not eat.

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Rosy Maple Moths Emerging, Mating & Laying Eggs

6-13-16  rosy maple moth 059Rosy Maple Moths (Dryocampa rubicunda) are easy to recognize, with their pink and yellow woolly bodies, pink legs and pink antennae.  Many adults are emerging from their pupal cases now, having spent the winter underground as pupae. Once metamorphosis is complete, the adult moths lose no time in finding mates and laying eggs, not stopping to even eat.  These members of the family Saturniidae are most active during the first third of the night, reducing their body temperature and activity in the morning and afternoon.

Mating takes place at night on the underside of a leaf, and 24 hours later the female lays clusters of 10-30 eggs (a total of 150 – 200 eggs) on the underside of the leaves of the larvae’s host plants, most often maples and oaks.  When the eggs hatch, the larvae usually remain on the same tree throughout their larval stage.

Known as Green-striped Mapleworms, the larvae initially feed together, but become independent feeders as they age.  Mapleworms change color as they develop.  When young, most have black heads and yellow bodies, but with age their heads turns reddish-brown and their bodies assume a shade of green.

In New England there is only one brood per summer; further south, there are multiple broods.

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Promethea Pupae Parasitized

12-21-15 promethea cocoon 257Although a lack of snow makes tracks difficult to find, there are other, more permanent, animal signs such as bird nests and cocoons that are visible this time of year. Among the more obvious is the cocoon of the Promethea Moth – a giant silk moth. When the time for pupating arrives the Promethea caterpillar selects a leaf and strengthens its attachment to the tree by spinning silk around the petiole of the leaf as well as the branch it grows on (to assure that it doesn’t fall off the tree). With more silk it rolls the leaf up into a tube and then proceeds to spin its cocoon inside the rolled-up leaf, leaving a valve-like structure at the top of the cocoon through which the adult moth exits in the spring.

Unfortunately for silk moths, many are parasitized by flies and wasps (there are nearly 100 natural parasites that affect the 24 species of silk moths east of the Mississippi River). Frequently flies or wasps lay their eggs in silk moth caterpillars and then develop inside them. Eventually the fly or wasp larva secretes a substance that causes the caterpillar to pupate, at which time the fly or wasp also pupates and then exits the moth pupa and cocoon (see exit hole in smaller photo), causing the death of the moth pupa. Silk moth populations are decreasing, in part as a result of these parasitoids. Among others, a non-native parasitic tachinid fly, Compsilura concinnata, is wreaking havoc on silk moths.

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Snowberry Clearwing Larvae Pupating

snowberry clearwing larvae 125The Snowberry Clearwing (Hemaris diffinis), a type of Sphinx moth, is one of several daytime-flying “hummingbird moths,” so-called because of their ability to hover while drinking nectar from a flower, and because of the humming sound they make, much like a hummingbird. The yellow and black bands of the Snowberry Clearwing’s abdomen also cause it to be mistaken for a bumblebee. The most distinctive thing about this moth is that a large portion of its wings are transparent, due to scales falling off.

Snowberry Clearwings are often seen around the time that beebalm is in bloom, in July and August. The females entice the males with a pheromone that they produce from glands at the tip of their abdomen. After mating, the females lay their tiny, round, green eggs on their larval food plants. Like many Sphinx moths, the larvae have “horns” at the end of their bodies. Most Snowberry Clearwing larvae are green, but they can be brown, as well. Both colors enable them to be well camouflaged as they feed on the leaves of honeysuckle, viburnum, hawthorn, snowberry, cherry, mint, and plum. The caterpillars are active until late fall, when they drop to the ground, spin a loose cocoon and pupate, partially protected by leaf litter. The pupa spends the winter hidden under the leaves, and the adult moth emerges the following spring. (Thanks to Tom Wetmore and Heidi Marcotte for photo opportunity.)

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Leaf Miners

9-29 leaf miners IMG_6836A leaf miner is the larval stage of an insect (primarily moths, sawflies and flies) that feeds on leaf plant tissue. Most of these insects feed for their entire larval period within the leaf, creating tunnels between the upper and lower leaf surfaces. Some will pupate within the leaf mine, while others cut their way out when they are full-grown and pupate in the soil.

The pattern of feeding tunnels, as well as the pattern of droppings, or frass, within them (darker sections of tunnels), combined with the species of plant on which they occur, can sometimes identify the species of insect that created the mines. A moth larva, the Common Aspen Leaf Miner (Phyllocnistis populiella), leaves delicate, serpentine mines (see photo) that are diagnostic of this species.

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