September 17, 2022 by Beth

Green Darner Migration

Common green darner female (Anax junius)

On a windy, warm September evening, the sun has set; the air is soft and dusky. Migration is underway, but not the avian sort. A few large common green darner dragonflies zigzag beneath the trees hawking insects. I look skyward and far above me, a river of swarming green darners surges — hundreds of them — straight south ahead of a cold front.

Born in Minnesota, these green darners migrate to the Gulf Coast of the southern United States and Mexico. When they arrive, they’ll mate and lay eggs to produce the next generation, which will migrate north in April or May. When they arrive here, they will mate and give rise to a new generation before dying. These progeny will hatch by late August and continue the cycle of migration and reproduction.

But that’s not the entire story! Common green darners are present in the north all summer — so where did they come from? There’s a resident population that doesn’t migrate. They’re active and deposit eggs throughout the summer and autumn. However, their young, called naiads, won’t mature until the following spring. They will wait out the winter on the bottom of a pond, marsh or slow-moving river or stream.

Averaging 3 inches in length, and with a wingspan of 3.5 inches, green darners are among our largest dragonflies. This one also is a female. Males’ abdomens are bright blue.

Green darner adults eat mosquitoes, midges and other flying insects. The aquatic naiads feast on mosquito larvae and other aquatic insects, tadpoles and tiny fish. Green darners are eaten by spiders, large robber flies and birds such as kestrels.

Further Reading

Mead, Kurt. (2009). Dragonflies of the North Woods. Duluth, Minnesota: Kollath & Stensaas Publishing.

Smithsonian Magazine

UW-Milwaukee Field Station

August 20, 2022 by Beth

Hidden Music Maker

*Katydids’ green bodies are easily mistaken for plant leaves. Can you spot one under the flower on the right?*

Walk outside and listen on a late-summer or early autumn evening. Insect music has replaced the chorus of robins, mourning doves, northern cardinals and other birds. The new songsters might include tree and field crickets, cicadas, grasshoppers and katydids.

Unlike their more somber-colored cricket cousins, katydids are often bright green and are well camouflaged by plant leaves and stems. Very long antennae and wings held vertically over the body distinguish them from grasshoppers. Many could pass for a small leaf on a plant! I often hear katydids calling, but rarely see them.

Similar to their cricket kin, katydids create sound by rapidly moving the sharp edge of one wing against a ridge of bumps on the other wing — this is called stridulation. Each species creates a different sound. Most produce clicks, rattles or buzzes that differ in pitch, pattern and volume. Only one species, the common true katydid (Pterophylla camellifolia) “says” its name. (The link includes both group and individual recordings.)

*Katydids’ ears are located below the knee joint. Zoom in to see the small, dark oval shapes called tympanum.*

Katydids have narrow hearing organs located below each knee on their front legs. Though the location differs from mammalian ears, the ear structure is similar to our own. Simply put, sound waves cause a katydid’s eardrums to vibrate. The vibrations rock a small plate that transmits sound waves to the auditory vesicle, which contains fluid. The waves move through the fluid over tiny sensory cells that glean information and send electrical impulses to the katydid’s brain. Scientists theorize that locating a mate and avoiding predators are two key purposes of katydid hearing.

What eats katydids? Owls, kestrels, other birds, rodents, tree frogs, insects and spiders prey on them. Mainly vegetarians, katydids eat leaves and flowers of plants, but sometimes eat insects — including other katydids!

Next time you’re outside in the evening, listen for katydid calls. Crickets aren’t the only nighttime musicians!

Further Reading

Katydids – Wisconsin Horticulture

Katydids – Tettigoniidae

Songs of Insects

October 14, 2021 by Beth

Wooly Bear Caterpillars

I found this little wooly bear asleep in the garden under a pile of fallen leaves and tucked it back in for the winter.

I miss the hum and activity of bees, butterflies and other insects that populate our garden. But, as I finished up some outdoor work, I was reminded that their absence is temporary. I spotted a familiar small, fuzzy form: a banded wooly bear caterpillar (Pyrrharctia isabella) asleep for the winter beneath some fallen leaves.

Though we usually call these little creatures wooly bears or wooly worms, there are more than 260 different species of them in North America. Each has a different coloration and becomes a distinct species of moth. The banded wooly bear is black on both ends with rusty orange in the middle. When the caterpillar reaches maturity, it becomes an Isabella tiger moth. Though I’ve seen many banded wooly bears, I have yet to see the moth, which is usually a muted orange, salmon or yellow color with black spots on its body and wings.

Wooly bears are generalists — they eat many types of plants including grass, clover and weeds. This one had just crossed the Lake Nokomis walking path in Minneapolis.

The banded wooly bear caterpillar grows up to 2 inches in length. Its fuzzy body is covered in tiny bristles called setae that are black on the caterpillar’s ends and rusty orange in the middle. The number of orange segments increases as the caterpillar grows. Though a few people might be sensitive to the bristles, most have no problems handling the caterpillars. I remember carrying them around as a child and holding them with our toddler son on nature walks.

Is it true that the size of a wooly bear’s orange band predicts the quality of the winter ahead? No, according to the sources that I read (please see the list below). Explanations include: the size of the orange band increases as the caterpillar grows; those with more orange grew up in a drier habitat and those with more black segments grew up where it was moister; lots of variety occurs naturally among caterpillar populations; and there’s plenty of disagreement among all of these views. In spite of the arguments, it’s fun to observe, compare and chart the size of wooly bears bands — especially with children!

Banded wooly bears in Canada and the northern United States typically produce one brood each year, though two generations are possible. Those that hatch in August feed until late autumn. They eat a broad range of grass, weeds and wildflowers, and aren’t crop pests. In autumn, they enter quiescence (a type of insect dormancy) for the winter, usually in leaf litter, or under a log or rock.

Look for wooly bears on sunny, mild autumn days. This one crossed the Sakatah Singing Hills Trail in southern Minnesota.

How do they survive our harsh winter? They produce a cryoprotectant,¹ an antifreeze to prevent cells from rupturing when they repeatedly freeze and thaw. The bristles or setae also help the caterpillar to freeze on the outside first, protecting the inner organs. In the spring, each caterpillar will awaken from quiescence, resume feeding and spin its cocoon. About two weeks later, an adult Isabella tiger moth will emerge.

Banded wooly bears range throughout the United States, Canada and even into Mexico. You might catch a glimpse of them feeding in the spring, but it’s more likely that you’ll spot one in autumn when you’re out walking, biking, or working in your garden.

wooly-bear-caterpillar-tom-2

Sources List for Further Reading

The Infinite Spider Blog

Minnesota Department of Natural Resources

NPR Science Friday video

National Weather Service

Scientific American Blog

University of Wisconsin – Milwaukee: Bug of the Week Blog

^¹The cryoprotectant is produced by other wooly bear species, too. In fact, the Arctic wooly bear (Gynaephora groenlandica) caterpillar has a life cycle that stretches over seven or more years! The Arctic summers are so brief that the caterpillars must feed and enter quiescence repeatedly for several years before gaining enough biomass to metamorphose into a moth. Overall, they spend 90 percent of their lives dormant and frozen! (For more about the Arctic wooly bear, follow the link above to the Scientific American Blog.)

December 13, 2020 by Beth

Winter Crane Flies

Maple and basswood line the banks of the Mississippi River.

We hike along the Mississippi River as a cloudless sky, calm wind and a mild 52°F settle in for the afternoon. (The average high for Minneapolis-Saint Paul is 28°F today.) Blue jays, black-capped chickadees, and red-bellied woodpeckers call; gray squirrels rattle through the crisp fallen leaves. The river’s surface is unmarked by ripple or wave, and two Canada geese float a few feet from shore, honking softly to each other.

Winter crane flies (Trichocera species) swarm and mate on mild winter days.

Wherever rays of winter sunlight stream through bare branches of basswood and maple, the air shimmers with small swarms of winter crane flies. The low December sun ignites their wispy forms into sparks of gold. They zip around as energetically as though it were July.

Most types of crane flies are abundant in summer. Just a few species mature and mate in the winter. The swarms shimmering in the afternoon sun consist mainly of males. Females join them briefly to mate, and then lay their eggs in rotting leaves and soil. When not in flight on mild days, the adults rest in protected areas such as hollow trees and caves. (What could they possibly find to eat during a Minnesota winter? Not much. In fact, adults typically don’t eat at all! The larvae eat rotting vegetation, fungi and animal scat.)

They sparkle like tiny gold jewels in patches of winter sunlight.

Winter crane flies are most common in late autumn, early spring and sometimes on mild winter days. Today, they never stray from the sun’s mild warmth — nor do we! A rare Minnesota December day, indeed, and one to remember when winter weather returns.

A Stick isn’t Always a Stick!

This northern walkingstick (Diapheromera femorata) is close to 4 inches long and is most likely a young insect or nymph, which are light green.

The northern or common walkingstick insect is a master of mimicry. Slender, green or brown, nocturnal and timid, it looks like a twig or branchlet. I’ve only spotted a few at our cabin in Central Minnesota over several years’ time. They were brown — except for this one, which was pearly green and sitting on the side of our cabin.

Since they are wingless, slow-moving and don’t bite, northern walkingsticks need some way to elude their predators — mainly songbirds and parasitic insects. They are extraordinary mimics and blend in perfectly with tree branchlets and twigs. Unless you spot them crawling, or they roost on a building or another object, it’s very difficult to see them. Males are brown and about three inches long. Females are greenish brown and closer to four inches in length.

So what do walkingsticks do? They are primarily nocturnal and rest during the day extending their front legs forward next to their antennae, which makes them appear more sticklike. At night they eat! The larval stages eat leaves of shrubs that are close to the ground, especially hazel, rose, blueberry and serviceberry. Adults feed in the tops of trees and appear to favor oaks, basswood, black locust and black cherry. When eating, they often sway like the leaves and branches around them, which provides greater camophlage.

Walkingsticks fold their front legs straight forward, next to their antennae, to appear more sticklike.

Northern walkingsticks mate in the afternoon and evening from late summer to mid-autumn. The female lays her eggs from high up in the trees. The eggs just drop to the ground to overwinter in the leaves. In the south, the eggs hatch the following spring. In the northern states and provinces, there’s a two-year cycle in which the eggs don’t hatch until the second spring. So, in Minnesota, the odd-numbered years produce many young and the even-numbered years produce fewer insects. The newly hatched larvae, or nymphs, climb up into shrubs where they molt several times before reaching adulthood. They are miniatures of their parents, but are green like new spring leaves.

We have just one species of walkingstick in Minnesota — it lives in the eastern United States and the southern portions of adjacent Canadian provinces. Most of the world’s 3000 stick insects live in the tropics.

Ebony Jewelwing

What do you associate with the words “winged beauties”? Many would answer birds and butterflies — and I’d add damselflies and dragonflies, too. On a sunny, warm morning, a pair of inky black wings flutter near the Snake River. At first I think it’s a butterfly, but a closer look reveals the electric-blue-green body of a male ebony jewelwing damselfly; he flashes cool and iridescent in the morning sun.

Inky black wings and a blue-green abdomen identify this male ebony jewelwing (Calopteryx maculata).

A member of the broad-winged damselflies, ebony jewelwings fly more like a butterfly than like their dragonfly relatives. Their wings are 1-to-1½ inches long and their body length is up to 2¼ inches. The male’s colorful abdomen — green, teal, blue, even a hint of purple — shimmers in the sunlight. A female ebony jewelwing is similar in appearance, but not as showy as a male. Her body is brown with little bits of blue or green. Her wings are more transparent black and display a distinct white spot near each tip. (See a female at Wisconsin Odonata Survey.)

In the eastern United States and southeastern Canada, look for ebony jewelwings perched along shady banks of shallow streams and slow-moving rivers from late May until September. Adults live for about 20 days. A mating pair will often fly attached in the heart-shaped “wheel formation” and remain connected for several hours. Females deposit eggs inside of submerged water plant stems in quiet sections of streams or rivers. The larvae or naiads live in the water for about a year and eat other aquatic larvae, such as mosquitos and mayflies. Adults eat most soft-bodied insects, for example small moths, mosquitos, mayflies, gnats, flying ants and termites.

The Snake River in east-central Minnesota provides the habitat needed by ebony jewelwings.

Even though jewelwings are voracious predators, they serve as supper to other creatures — turtles, frogs, fish, bats and birds, such as red-winged blackbirds, blue jays, flycatchers, purple martins and kingfishers.

How does one distinguish between a damselfly and a dragonfly? A few simple differences make it easy to tell them apart. Generally, damsels hold their wings folded vertically above their body, while dragons spread them horizontally when resting. Damselfly abdomens are more slender than the stout dragonflies’. Damselfly eyes are set far apart on the sides of the head, but dragonfly eyes wrap around and touch on top of the head.

A green darner dragonfly (Anax junius) exhibits the horizontal wings, stout body and wrap-around eyes characteristic of dragonflies.

Vertically folded wings, a slender body and eyes set far apart on each side of the head are characteristic of the ebony jewelwing and other damselflies.

Damselflies and dragonflies belong to the order Odonata, which means “toothed ones.” Many come in beautiful, iridescent color combinations. Fossil records indicate that Protodonata, the ancient ancestors of both dragons and damsels, arose about 325 million years ago. The first Odonata fossils are dated at a little older than 250 million years, which means they’ve inhabited Earth’s skies since before dinosaurs existed. I love to watch and think about these ancient, graceful creatures that add so much beauty to our woods and gardens.

August 28, 2018 by Beth

Late Summer Along Minnesota’s Snake River

Bottle gentians (Gentians andrewsii) signal the arrival of late summer in east central Minnesota.

Much as I hate to admit it, (since I’m a big fan of sun and warmth), the unmistakable signs of late summer color the banks of the Snake River in Pine County, MN. After 36 summers and autumns along the river, I know them well.

A female long-horned bee (Melissodes, spp.) pollinates a tall sunflower (Helianthus giganteus).

The season’s first bottle gentians, ironweed, tall sunflowers, native field thistle, Joe-Pye and goldenrod add their showy flowers to black-eyed Susan’s, fleabane, monarda and coneflowers already in bloom. Riverbank grapes turn dusky blue, dogwood berries ripen to white on scarlet stems, wild rose hips, hawthorns and chokecherries hang plump and red.

It’s a productive year for the bur oaks. Acorns fall like small rocks that bounce and roll down the roof before they plunk onto the wooden decks. Chipmunks, squirrels and mice snatch up ripe hickory nuts and soon the hazelnuts will be ready. As hard as I’ve tried, I’ve never beaten the squirrels to the tasty hazelnuts.

Crickets and katydids sing in place of wood thrushes and robins. Thank goodness for cardinals that sing at dawn and dusk, and for the melodic cooing of mourning doves during the hot afternoons.

It’s all lovely, and I wouldn’t change it — perhaps stretch it out further into the year — but this late-summer beauty makes me wistful for abundant hours of sunlight, wide-open windows, warm breezes and a simple outfit of shorts and a T-shirt. Let’s hope for a long, mild autumn.

Our neighbor, Ed’s, puple coneflowers (Echinacea purpurea) attract many species of butterflies.

Native field thistles (Cirsium discolor) provide pollen and nectar to insects and nutritious seeds for birds and other creatures.

Green-headed coneflowers (Rudbeckia laciniata) provide pollen to bees later in the fall. A hover or flower fly (Toxomerus geminatus) rests on the bloom.

Bur or mossycup oaks (Quercus macrocarpa), a type of white oak, are named for the fringe that surrounds the top of the acorn cup. They are an important food source for many birds and animals.

Riverbank or frost grapes (Vitis riparia) are a native Minnesota grape that favors a moist environment and feeds many bird species.

Gray dogwood berries, or drupes (Cornus racemosa) are a favorite of thrushes, robins and other birds.

Black-eyed Susans (Rudbeckia hirta) mix with fleabane and field thistle in a colorful patch next to the road.

August 16, 2018 by Beth

Garden Bugs: Nifty or Nasty?

Like most of life, my garden is a mix of good and not so great: desirable plants and weeds, loamy soil and heavy clay, beneficial insects and annoying pests — and early August brought many types of insects to our garden. Here are just a few stand-outs.

Japanese beetles (Popillia japonica), an invasive species, are a type of scarab beetle that destroy many plant species in North America.

The biggest pest in our yard is the Japanese beetle, which skeletonizes the flowers and leaves of many plants. A few weeks ago they favored apple and crabapple trees, but I’ve also pulled them off of my rose, asters, day lilies and purple coneflowers. Now, they are shredding my hosta and anise hyssop blossoms. According to the Minnesota Department of Natural Resources, the beetles are native to northern Japan and probably arrived in a shipment of iris bulbs in 1916. They have no natural predators, although some birds, such as starlings, robins, bluejays and sparrows will sometimes eat the adult beetles and the grubs, which live in lawns.

Yesterday I picked 46 beetles off of my royal standard hostas. I used to squish them, but that releases their pheromones, which attract more beetles. Now I pick them off by hand and drop them in a small pail of soapy water, which kills them quickly without releasing their pheromones. I don’t use an insecticide because so many beneficial insects would die from the chemicals.

The convergent lady beetle (Hippodamia convergens) is a North American native that feeds on aphids, whiteflies and other pests.

Not all ladybugs are red or orange. The tiny esteemed ladybug (Hyperaspis proba) is black with yellow spots.

Unlike the Japanese beetle, ladybugs, or ladybird beetles, especially those native to North America, are beneficial to gardens. More than 500 species of ladybugs have been identified in the United States. Mom taught us never to harm ladybugs because they eat aphids, a major garden pest. Our native ladybugs don’t bite, so if you feel a pinch and find it’s from a ladybug, it is likely to be an Asian ladybug, which do nip — mainly because they seek moisture and salt, or they feel threatened. Asian ladybugs were imported in the 1970s to help destroy predators in agricultural operations. I let them be when I find them because they destroy so many aphids and other pests. However, the native ladybugs are better suited to our gardens and plant species.

Aphids, that favorite food of ladybugs, are tiny, often wingless, and very plentiful. There are more than 300 species of aphids in Minnesota and they are found on all types of plants. Most aphids on a plant are females that reproduce asexually, without having to mate. They also give birth instead of laying eggs. The newborns are clones of their mother, so they, too, are female. (Environmental conditions sometimes cause females to produce both female and male offspring, which are genetically identical to the mother, except that males lack one sex chromosome.) They come in many different colors. I’ve seen green, black, red, and I have orange ones on some of my milkweed plants. When aphids suck a plant’s sap, it causes curling, yellowing and browning of the leaves. Aphids also secrete a sticky, sweet liquid called honeydew. Last summer, during a heavy infestation of aphids, my milkweed plants were dripping with honeydew and covered with ants, which are attracted to the sweet liquid. Even though I washed the milkweed with water from the garden hose daily, the plants were disfigured and messy.

Tiny soft-bodied aphids (Aphids nerii) suck plant juices from common milkweed. The white specks are moltings that are stuck in the honeydew.

This juvenile male eastern pondhawk (Erythemis simplicicollis) will attack any type of insect its own size or smaller, including others of the same species.

In contrast to the slow, rather clumsy flight of beetles, several species of dragonfly dart and swoop among the garden plants. Perched on a milkweed leaf, a green eastern pondhawk zips lightning-quick from its perch to capture a fly. Its powerful jaws quickly crush and consume its prey. Common in gardens, dragonflies eat mosquitoes, gnats, flies and other insects. Their shining colors add beauty to the garden.

Most meadowhawks (Sympetrum spp.) fly in late summer and autumn.

Monarchs, red admirals and other butterflies are frequent visitors to our garden — especially now when the milkweed is blooming and the plants are in their prime for feeding monarch larvae. These tiny caterpillars feed only on milkweed and I discovered two of them a week ago. Adult monarchs sail through the garden stopping to nectar on milkweed, Joe-Pye, garden phlox and purple coneflowers.

Monarch caterpillars hatch and grow only on milkweed plants.

Adult monarchs (Danaus plexippus) and many other butterfly species nectar on common milkweed (Asclepias syriaca).

A red admiral (Vanessa atalanta) nectars on garden phlox (Phlox paniculata).

Red admirals are smaller and fly faster and more erratically than monarchs. A male finds a sunny spot and watches for a female to fly by. After mating, the female lays eggs on nettle plants. Adults nectar on milkweed, red clover, ripe fruit and tree sap. They are one of the few species that overwinter in Minnesota, often in a wood pile or mound of leaves.

The summer garden harbors so many interesting, and often beautiful, insects. Next time you’re working in your garden, or simply enjoying your yard, take a look at the diversity of these tiny creatures all around us. The majority of them are either beneficial or harmless. Nifty or nasty? You decide!

August 18, 2017 by Beth

Lake Michigan Walk

In August, many wildflowers begin to bloom in the Upper Midwest. Bees, wasps, moths and butterflies visit them for nectar and pollen. While in Milwaukee, Wisconsin, last weekend, we walked along Lake Michigan to enjoy the warm sun, gentle breeze and flowers both native and non-native that grace the shoreline. Among the blooms were chicory, Queen Anne’s lace, everlasting pea, goldenrod, sweet clover, gray-headed coneflower, bouncing Bet, red clover, Black-eyed Susan, monarda and lesser burdock. (If you look closely, you’ll spot a few pollinators, too.)

June 21, 2017 by Beth

Summer Solstice

The first wild rose (Rosa blanda) of early summer.

It is the season of light in the North. Earth bows its northern pole to the sun extending daylight to almost sixteen hours — eight more since winter solstice last December. Spring flowers are finished blooming, trees are fully covered in lush green leaves, and swelling buds on many perennials will open soon. Fireflies glow in the night. During the day, delicate lacewings, damselflies and dragonflies patrol the garden for pests. I spotted my first monarch of the season a couple of weeks ago when it visited our milkweed patch, which is almost ready to bloom.

Solstice was mild and clear with a high of 76℉. I enjoyed the company of good friends for lunch at an outdoor restaurant. Later, I sat in our garden to soak up the late-afternoon sun’s warmth, to listen to the robins sing and to toast the long summer ahead.