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View from Mt. Tom in high summer (Woodstock, VT) K.P. McFarland

Field Guide to August 2023

The dog days of summer are here, hot and sultry. The Romans referred to this time of year as the days of the dog star, when Sirius appears in the sky just before the sun and marks the hottest days of summer. Read all about August's natural wonders in this month's field guide.

By Vermont Center for Ecostudies August 16, 2023
Primrose Moth (Schinia florida) on its namesake plant Bryan Pfeiffer
Primrose Moth (Schinia florida) on its namesake plant Bryan Pfeiffer

Primrose: A Plant and a Moth

By Melory Brandao

Common Evening Primrose (Oenothera biennis) is a native wildflower of open fields, roadsides, and other disturbed areas. This biennial grows two to six feet high with green or red, leafy stems covered in tiny white hairs. Its four-petaled flowers are bright yellow and have a mild lemon scent. They bloom from late spring into late summer, opening every night and closing around noon. Although Evening Primroses produce no blossoms until their second year, they self-seed exceptionally well and support a variety of pollinators and other wildlife.

Hawkmoths, bees, and hummingbirds visit this flower for its nectar, and goldfinches can be seen foraging on its seeds well into the fall. Primroses are particularly vital to the Primrose Moth (Schinia florida), an endearing species that has a specialized bond with this plant.

Adult Primrose Moths are bright pink with a creamy white to yellow thorax and abdomen and a pale yellow margin at the tip of their wings. Females lay eggs on the buds of their host plant, which serve as food for the caterpillars once they hatch. After growing through several molts, Primrose Moth caterpillars dig into the soil, where they pupate and overwinter within a few inches of the surface. Just as Evening Primroses develop their buds the following summer, pink and yellow adults emerge from the ground and repeat the year-long cycle.

If Evening Primroses grow in your garden, peek inside a closed flower, and you might find a Primrose Moth resting there.

13744, , primrosemothlarvae_580x800_acf_cropped, , , image/jpeg,, 580, 800, Array, Array Laura Gaudette -
Primrose Moth caterpillar, green morph Laura Gaudette -
13743, , primrosemothpinkmorph_580x800_acf_cropped, , , image/jpeg,, 580, 800, Array, Array Rebecca Cowser -
Primrose Moth caterpillar, pink morph Rebecca Cowser -

Unlike most caterpillars that happily feast on leaves, Schinia florida feeds on its host plant’s seed capsules and flowers. Primrose Moth caterpillars convincingly mimic primrose seed pods, which they’ll bore into and eat until the seed pod is hollow. The caterpillars are usually green with a reddish hue towards the head, but some individuals appear bright pink.

Primrose seeds released from the pod  annkatrinrose -
Primrose seeds released from the pod annkatrinrose -

If you’d like to support this unique moth species, you can purchase seeds from a local nursery like the Vermont Wildflower Farm. You can also easily collect your own seeds. The seed pods mature in late summer through the fall, turning brown from the tip downward. Once you see brown at the top of the pod, the seeds are ready for collection. Tilt the pod towards the inside of a paper bag or plastic container to catch the falling seeds, which can number in the hundreds. To plant the seeds, scatter them over loose soil in late fall or early spring and cover them lightly with soil.

13720, , Splachnum 1, , , image/jpeg,, 1875, 2500, Array, Array Grace Glynn
This clump of Dung Moss was found in a dwarf shrub bog among stunted Black Spruce. The dung substrate had already humified, leaving a tiny clearing behind. Grace Glynn
13721, , Splachnum 2, , , image/jpeg,, 1888, 2500, Array, Array Grace Glynn
The inflated balloon-like structure below the capsule acts as a landing platform for dung flies, which are attracted by volatile compounds secreted by the moss. Grace Glynn
13722, , Splachnum 3, , , image/jpeg,, 1875, 2500, Array, Array Grace Glynn
A bunch of capsules with beautiful reds, yellows, and gold Grace Glynn

The Dung, the Moss, and the Fly

By Grace Glynn, Vermont Department of Fish & Wildlife Botanist

Dung Moss (Splachnum ampullaceum) is found only on the dung of large boreal herbivores in peatlands. In Vermont, that usually means Moose scat in bogs. The clump shown above was found in a northerly dwarf shrub bog among stunted Black Spruce. Its dung substrate had already humified, leaving a tiny clearing behind.

The inflated balloon-like structure below the capsule acts as a landing platform for dung flies, which are attracted by volatile compounds secreted by the moss. The flies unknowingly pick up spores and carry them around to other piles of dung, and there you have it: an entomophilous moss. The sporophytes are vibrant and showy. Elizabeth Britton once described them as “fairy parasols, red and yellow, that is what they seem to be, not ordinary umbrellas meant to be taken out into the rain, but bright, gay, silky, showy things…”

The family Splachnaceae includes the only spore-bearing plants in the world known to harness the power of insects for dispersal. Some species in the family, such as Vermont’s very rare Slender Cruet-moss (Tetraplodon mnioides), grow exclusively on bones and carnivore scat.

Though widely distributed in Britain and North America, Dung Moss is rare across its range, including in Vermont, where it’s ranked as rare (S2). In some parts of the world, it has likely declined because of peatland draining. Just another reason to restore and preserve peatlands and all their bright, pungent gems.

Juvenile Black-throated Blue Warbler male banded on Mt. Mansfield, Vermont K.P. McFarland
Juvenile Black-throated Blue Warbler male banded on Mt. Mansfield, Vermont K.P. McFarland

Time to Hit the Hills

By Jason Hill

As summer edges into fall, juvenile birds are starting to make their own way in the world. Independent at last, some born in hardwood forests take a surprising turn toward high elevations before the onset of migration. That’s where a late-spring snowpack and colder temperatures overall tend to delay the peak in invertebrate and fruit abundance compared to areas downslope. A mountain’s shorter growing season can mean that food for young birds peaks more intensely than it does in forests at lower elevations.

Here in New England, August is a delightful time to encounter hardwood bird species atop our tallest mountains. Species such as Black-throated Blue Warbler, Ovenbird, Canada Warbler, and Black-and-White Warbler all make their way to the spruce-fir zone. When examining three years of banding data from Mount Mansfield, VCE scientists Chris Rimmer and Kent McFarland found that juvenile birds overwhelmingly predominated August and September captures of those four species. Out of 443 netted individuals, 97% were hatch-year birds.

A Great Golden Digger Wasp carries a katydid. K.P. McFarland
A Great Golden Digger Wasp carries a katydid. K.P. McFarland

Great Golden Digger Wasps on the Hunt

By Kent McFarland

Great Golden Digger Wasps (Sphex ichneumoneus) hunt for grasshoppers, katydids, and crickets—not to eat but to feed their young. After paralyzing their victim with a sting, they place it in an underground chamber and then lay a single egg on it. The immobilized victim remains alive, providing fresh food for the hatched larva. House Sparrows (Passer domesticus) and American Robins (Turdus migratorius) have been observed chasing wasps carrying prey, causing them to surrender the food to their pursuers. The wasps produce one generation per year, with young wasps spending winter in their nests and emerging the following summer. For their own meals, adults visit flowers and feed on nectar. Keep an eye out for other wasp species that specialize in hunting spiders, bees, stink bugs, cicadas, and other species for their young to feed on. It’s a dangerous world for unsuspecting invertebrates.

Northern Dog-day Cicada, Woodstock, Vermont K.P. McFarland
Northern Dog-day Cicada, Woodstock, Vermont K.P. McFarland

Dog Day Buzz

By Kent McFarland

The dog days of summer are upon us, and so is the buzzing sound of the Northern Dog-day Cicada. Males are calling to females with a high-pitched buzz lasting about 15 seconds. It starts softly, gets louder, then tapers off—like a buzz saw.

August’s lazy, hot, dog days are named for Sirius, the “dog star” in the constellation Canis Major. Sirius appears in northern skies around the same time that this cicada emerges and starts singing.

Close-up of male cicada tymbal.

Males produce the buzz using a pair of ribbed membranes, called tymbals, located at the base of their abdomens. A muscle pulls all the tymbal ribs inward. The ribs make a short, sharp noise when they snap inward and outward. The cicada repeats this 300 to 400 times per second to create the buzz, which can be heard up to a quarter-mile away, and hopefully entice a female. If she’s interested in the song, she snaps her wings. The males hear this and move closer and closer, hoping to mate eventually.

Female cicadas use their ovipositors to saw small gashes into tree twigs, where they lay eggs. After about six weeks, the nymphs hatch, drop to the ground, burrow down to a tree root, and suck its juices for about three years. Then one July or August day, Dog-day Cicadas crawl out of the ground and climb up tree trunks as mature nymphs, where they split open and emerge as adults with long wings and bulging eyes—only to live for a few weeks.

Hear cicadas or other insects singing? Make a recording with your smartphone and submit them to the Vermont Atlas of Life iNaturalist project. It’s fun and easy!

Katydid at night K.P. McFarland
Katydid at night K.P. McFarland


By Kent McFarland

Katydids can evoke childhood memories of summer as we pause to listen to their distinct sound. In Vermont, there are 20 known species, three of them introduced. Each species has its own distinctive sound, just like birds.

A katydid’s front wings feature a file and a scraper. The file looks a little like the teeth of a comb, and the scraper is just a sharp edge. To produce their familiar sound, they elevate their front wings and move them back and forth against each other, the scraper on one wing moving along the file of the other. This action, called stridulation, makes membranes on the wings vibrate, which is the source of the sound we’ve been hearing since we were kids.

But katydids don’t have ears on the sides of their heads like we do. They have them on their knees… or their elbows… either way—they have an ear-like structure called a tympanum, which is a tiny oval cavity with a thin membrane stretched over it that vibrates in response to sound, much like our own eardrum.

Hear katydids or other insects singing? Make a recording with your smartphone and submit them to the Vermont Atlas of Life iNaturalist project. Be sure to add the air temperature to your observation. This affects the song’s tempo, which slows down as air cools and speeds up as it warms. Your audio recording and temperature observation may one day help an expert identify your katydid to species.

10393, , Aphrodite-Fritillary20130810KPMcFarland_580x400_acf_cropped, , , image/jpeg,, 580, 400, Array, Array K.P. McFarland
Aphrodite Fritillary K.P. McFarland
10390, , Atlantis-Fritillary20120819KPMcFarland_580x400_acf_cropped, , , image/jpeg,, 580, 400, Array, Array K.P. McFarland
Atlantis Fritillary K.P. McFarland
10392, , Great-Spangled-Frit-Ed-Sharron-cc_580x400_acf_cropped, , , image/jpeg,, 580, 400, Array, Array K.P. McFarland
Great Spangled Fritillary K.P. McFarland
13700, , Aphrodite-Fritillary20160922KPMcFarland_390x540_acf_cropped, , , image/jpeg,, 390, 540, Array, Array K.P. McFarland
Aphrodite K.P. McFarland
13703, , Atlantis-Fritillary20200722KPMcFarland_390x540_acf_cropped, , , image/jpeg,, 390, 540, Array, Array K.P. McFarland
Atlantis Fritillary K.P. McFarland
13702, , Great-Spangled-Fritillary-nectaring-coneflower20100704KPMcFarland_390x540_acf_cropped, , , image/jpeg,, 390, 540, Array, Array K.P. McFarland
Great Spangled Fritillary K.P. McFarland

Watching Fast Fritillaries

By Kent McFarland

Summer is for fast-flying fritillaries. These orange and black speedsters streak around old fields and meadows, halting suddenly to taste the sweet nectar of a flower, and then off they go again. Just a few days ago, while butterfly-watching for a short time, I saw all three of Vermont’s greater fritillary species, the treasures of late summer.

Greater fritillary caterpillars strictly feed on violets. The adults lay eggs on or near these plants to ensure that larvae hatching in the fall will have ample food after they overwinter in the leaf litter without a meal and re-emerge when temperatures warm to eat. In their adult form, these butterflies are mostly orange with black spots, stripes, and bars. Their undersides are adorned with a silvery sheen of spots, giving them their alternate name of “silverspots.” For many butterfly watchers, they are quite tricky to tell apart at first.

The three species that occur in northern New England are Great Spangled Fritillary, Atlantis Fritillary, and Aphrodite Fritillary. A fourth, Regal Fritillary, was found here when New England was a more pastoral landscape. The last one known in Vermont was seen in the 1940s somewhere in Pomfret.

It wasn’t long ago that I had a terrible time identifying greater fritillaries in the field, but there are a few tricks here in New England that can help. Fritillaries in the West are a whole different ball game.

The first trick is to get a pair of close-focusing binoculars. I have a pair that will focus on my shoelaces. It opens up a whole new world. Many of you are probably bird watchers. Identifying butterflies takes the same skills; the field marks are just smaller! And with digital cameras, we can easily capture what we see to study later and share.

Now, look through those close-focusing binoculars and check out their eye color. Yes, that’s right, eye color. The Atlantis Fritillary has gray-blue eyes, like ocean water. The other two have amber or brown eyes. The Atlantis also tends to have bold, black wing margins on both the forewing and hindwing, but be careful; this can wear as the butterfly ages.

So now we have two amber-eyed species to sort out. Heck, we’re down to a 50:50 chance now!

Great Spangled Fritillaries tend to be the larger of the two, but size is often difficult as a field mark unless the difference is great. In this case, it isn’t that helpful because Aphrodite is also a fairly large butterfly in the East (smaller as you go westward). If you can get a look at the underside of the hindwings, you can usually nail the identification. Aphrodite Fritillaries have a very narrow yellow to cream-colored submarginal band (that’s the last cream-colored band before the silver spots on the edge of the wing). This band has a lot of brown scaling creeping into it, making it very narrow. The Great Spangled has a really wide submarginal band. Most, not all, Aphrodite have a beautiful rose blush on the underside of the forewing. The upper side can be a little tricky. Aphrodite Fritillaries have a black spot near the base of the forewing upper side, but this is quite small on some Aphrodite specimens and present on some Great Spangled specimens.

To help you visualize these and other field marks, check out some excellent field guide photos at the Maritime Butterfly Atlas for Great Spangled FritillaryAphrodite Fritillary, and Atlantis Fritillary.

It sounds hard, but once you begin to look closely, you’ll start to see these fritillaries in a whole new light. Be sure to share all of your butterfly images with our e-Butterfly project to be included in the Second Vermont Butterfly Atlas, and help us monitor butterflies throughout the state.

Comments (3)

  1. Abigail Reifsnyder says:

    So much to learn about!

  2. David Merker says:

    Great essays, well done VCE

  3. Charles dutelle says:

    This was one of your best presentations yet.I really enjoyed it.I live in can’t participate in your field deals but sure do enjoy your publication on the computer .Because of age and income my contributions aren’t what I’d like them to be but please keep up the good enjoyable publications.Have a picture somewhere that I took last year here of a meadow fritillary and a pearl crescent apparently mating which was a surprise.

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