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Field Guide to June

By Vermont Center for Ecostudies June 2, 2020

Here in Vermont, we dream of June during the darkest winter days. Verdant wooded hillsides glowing brightly under a robin egg sky. Warm afternoon breezes rolling through the valleys as we lounge by the clear waters of a cold river. The chorus of birds waking us each morning. The smell of freshly cut grass wafting through the window. Butterflies skipping from one flower to the next. We forget about the clouds of black flies, the hum of the mosquitoes and the rainy days. June is a dream here. Its days last forever. Here’s just a few of the natural history wonders for the month.

Canadian Tiger Swallowtail (Papilio canadensis) in Vermont. © K.P. McFarland - All Rights Reserved
Canadian Tiger Swallowtail (Papilio canadensis) in Vermont. © K.P. McFarland - All Rights Reserved

Confusing Flying Tigers

By Kent McFarland

And you thought you had trouble telling one butterfly species from another. The tiger swallowtail butterfly, a rather large, yellow butterfly with black tiger stripes, flutters over the hills and valleys of eastern North America each spring and early summer, sometimes in great numbers. But figuring out which tiger is which has baffled lepidopterists for more than three centuries.

The tiger swallowtail was the first New World butterfly to be painted by an artist from Europe. John White painted one on Roanoke Island, North Carolina, in 1587 while serving as the expedition leader of Sir Walter Raleigh’s third trip to America. Despite exaggerating the wing shape, his details were relatively accurate.

Linnaeus, the father of modern taxonomic naming, called the species Papilio glaucus in 1758. For over 150 years thereafter, it was commonly known as the tiger swallowtail. But Linnaeus had actually named the tiger swallowtail from a black-colored female – a rarer version of the group that looks just like the more common yellow females, except that the background color is darkly pigmented. These dark females generally occur from Massachusetts to Florida, the southern portion of the tiger’s domain.

Eastern Tiger Swallowtail (Papilio glaucus) dark form female nectaring on Buttonbush in Maryland. © K.P. McFarland - All Rights Reserved
Eastern Tiger Swallowtail (Papilio glaucus) dark form female nectaring on Buttonbush in Maryland. © K.P. McFarland - All Rights Reserved

Why are there dark-colored females? They are thought to have evolved to mimic the dark color of the foul-tasting and poisonous Pipevine Swallowtail butterfly. This is called Batesian mimicry, when one otherwise palatable species evolves to closely resemble an unpalatable cousin.

Linnaeus also observed the more common, yellow-colored female tiger swallowtail but decided it was another species altogether. A contemporary of Linnaeus documented a male tiger swallowtail, which is also yellow, but decided it, too, was its own species.

In the 1800s, biologists realized that the three species were only differentiated by color and lumped them together under the common name, “eastern tiger swallowtail.” Starting in at least 1906, however, lepidopterists noticed that the more northern populations were smaller and had slightly different markings. Some began recognizing this as a subspecies of the eastern tiger swallowtail and called it canadensis.

In 1991, biologists from Michigan State University announced that they had enough evidence to declare canadensis a separate species altogether – the Canadian Tiger Swallowtail. Their evidence included genetic differences, color and size differences, caterpillar food-plant use, lack of black-colored females in canadensis, and only a very narrow hybrid zone between the two species. It is now widely accepted that Eastern Tiger Swallowtails are found southward and Canadian Tiger Swallowtails are found northward.

The range of the Eastern Tiger Swallowtail just barely makes it into Vermont and New Hampshire. Most of the tiger swallowtails we see around here, therefore, are Canadian Tiger Swallowtails.

Generally, Canadian Tiger Swallowtails are flying around from the beginning of May until the end of June (later in higher elevations), while Eastern Tigers fly from June into October. So if you see a tiger swallowtail sailing over a meadow from mid- to late summer, it just might be an Eastern. But even up close, they look very similar. The Eastern is larger, with the underside marginal forewing band broken into yellow dots separated by black borders. On the underside of the Canadian hind wing, the black line nearest the body is very wide. Minute details for sure. Even worse is that, in the hybrid zone between species, there are many that appear intermediate. In Vermont and New Hampshire, we are in the thick of the intermediate zone.

But the story doesn’t end here. In 2002, another potential tiger was described by two lepidopterists, Harry Pavulaan and David Wright. “When it became apparent that there were inconsistencies in the natural history of mountain populations versus lowland populations of tiger swallowtails, an intensive effort was made to study the field biology of the mountain populations,” said Pavulaan. They have named it the Appalachian Tiger Swallowtail and affectionately refer to it as “Appy”. So far, it is known only from the central and southern Appalachian Mountains.

Appalachian Tiger Swallowtail (Papilio appalachiensis) at the Great Smokey Mountain NP -Oconalluftee Visitors Center. © K.P. McFarland - All Rights Reserved
Appalachian Tiger Swallowtail (Papilio appalachiensis) at the Great Smokey Mountain NP -Oconalluftee Visitors Center. © K.P. McFarland - All Rights Reserved

Why have tiger swallowtail identities been so hard to pin down? Probably because tiger swallowtails are comprised of sibling species – two or more populations that have become reproductively isolated from one another, yet so similar in outward appearance as to be lumped together even by experts. Careful, intense study of details such as anatomy, biochemistry, and behavior can bring sibling species to light. But there can be many dead ends and evolutionary tricks that confuse biologists.

If you want to wade into world of tiger identification, now is the time. The lovely Canadian Tiger Swallowtails are flitting over meadows near you. Learn more about the details of tiger swallowtail identification in this blog post from Bryan Pfeiffer. And be sure to add your observations to e-Butterfly.org.

 

Photo 1: https://www.kpmcfarland.com/Wildlife/Butterflies/Papilionidae/i-99qqT2J/A
Photo 2: https://www.kpmcfarland.com/Wildlife/Butterflies/Papilionidae/i-7cH4XC2/A
Photo 3: https://www.kpmcfarland.com/Wildlife/Butterflies/Papilionidae/i-m7mqTdt/A

10107, , pitcher-plant-1_580x400_acf_cropped, , , image/jpeg, https://vtecostudies.org/wp-content/uploads/2020/05/pitcher-plant-1_580x400_acf_cropped.jpg, 580, 400, Array, Array © jaylyonvt (iNaturalist) licensed under CC-BY-NC
Purple Pitcher Plant (Sarracenia purpurea) © jaylyonvt (iNaturalist) licensed under CC-BY-NC
10109, , pitcher-plant-flowers_580x400_acf_cropped, , , image/jpeg, https://vtecostudies.org/wp-content/uploads/2020/05/pitcher-plant-flowers_580x400_acf_cropped.jpg, 580, 400, Array, Array © Sean Beckett licensed under CC-BY-NC
Flowering Purple Pitcher Plants (Sarracenia purpurea) © Sean Beckett licensed under CC-BY-NC

A Pitcher Plant’s Web of Life

By Kent McFarland

Find yourself a sphagnum covered bog in New England and you’re sure to find a pitcher plant.  But peer a little closer and you’ll find a whole self-contained world within it.

Northern pitcher plants (Sarracenia purpurea) grow as a rosette and produce 6 to 12 new tubular leaves each season. A bunch of pitchers next to each other likely belong to the same individual. New leaves open every few weeks and the “pitcher” that is formed fills with rainwater. Leaves capture the sun for photosynthesis during their first year, but as they age they are used by the plant to capture prey for 1 to 2 years before they fall apart. The small prey die and break down in the pitcher. The plant absorbs nutrients from the prey that are not available from the acidic bog.

The prey are attracted to the pitcher by a sweet sugary secretion on the lip of pitchers, as well as color and scent. Because of a waxy, slippery coating on the lip of the pitcher, they sometimes fall into the water inside the pitcher and find it difficult to climb out because of very fine, downward-angled hairs on the walls of the leaf.

Nicholas Gotelli from the University of Vermont and Aaron Ellison from Harvard Forest studied the effects of increased inputs of atmospheric nitrogen from acid precipitation. They discovered that as more nitrogen is added to bogs the pitcher plants shift from producing water-filled pitcher-shaped leaves to flat leaves that are used for photosynthesis. This is an amazingly fast morphological change.

There is a complex web of life living within each pitcher. The base of the food web is comprised of captured prey, mostly ants and flies. These are shredded and partially consumed by Pitcher Plant Midge (Metriocnemus knabi) and Pitcher Plant Fly (Fletcherimyia fletcheri) larvae. Shredded prey are processed by a host of bacteria and protozoa. These are in turn prey to a filter-feeding rotifer (Habrotrocha rosi) and a mite (Sarraceniopus gibsonii). Larvae of the Pitcher Plant Mosquito (Wyeomyia smithii) feed on bacteria, protozoa, and rotifers. Older mosquito larvae (third instar) eat rotifers and smaller mosquito larvae (first and second instar).

Gotelli and Ellison found that the web of life extends outside of the pitcher too. The leaves exude a sugar that attracts ants. Some ants forage successfully while a few fall into the pitcher. Two moths, the Pitcher Plant Moth (Exyra fax) and The Pitcher Plant Borer (Papaipema appassionata), only use the Pitcher Plant as a host plant for their caterpillars to feed and grow. The larvae of the Pitcher Plant Moth can drain and kill individual pitchers. The Pitcher Plant Borer feeds on the roots and can sometimes kill the entire plant. Repeated or heavy feeding by the moth larvae reduces the amount of available sugar to the ants.

Check out the hidden world of the Pitcher Plant the next time you are on a boardwalk through a bog. Here are some bogs with boardwalks in Vermont:

 

Photo 1: https://www.inaturalist.org/observations/33563710
Photo 2: https://www.inaturalist.org/observations/27790769

Wood Turtle (Glyptemys insculpta) © mellohrer (from iNaturalist) licensed under CC-BY-NC
Wood Turtle (Glyptemys insculpta) © mellohrer (from iNaturalist) licensed under CC-BY-NC

A Slow and Stealthy Traveler

By Emily Anderson

When June’s heat starts to take hold, who does not want to take life a little slower? When it comes to masters of slowing down, look no further than the humble turtle. Vermont is home to seven turtle species, however there is one who is the subject of particular interest: the Wood Turtle. June marks the beginning of its active summer season. From June to September, Wood Turtles split their time between the streams where they overwinter and seek refuge, and their upland foraging grounds, at times traveling up to 1,000 feet. Wood Turtles are omnivores whose diet reflects their mixed habitat; they regularly consume fish, invertebrates, insect larvae, earthworms, and plants. By mid-June, females seek out nesting areas, at times traveling up to one mile to get there. They prefer to dig their nests in soft soils and often create several false ones before deciding where to lay their eggs.

Wood Turtles are important members of stream communities due to their role as indicators of stream health. In order to survive, they need clean water, relatively undeveloped upland habitat, and intact connections between their streams and foraging grounds. Many other Vermont animals, from trout to mink, require similar conditions, and benefit from measures that protect Wood Turtle habitat.

Where are all of Vermont’s Wood Turtles you ask? They are naturally elusive—even those who frequently visit Vermont’s streams may never encounter one. You may not even guess that they are found in all 14 counties! Unlike other turtles, which often bask on exposed rocks and logs, they prefer filtered light and vegetation to screen them from view. There is another important reason why they are difficult to find: they are rare. In fact, Wood Turtles are listed as a Species of Greatest Conservation Need in Vermont. Over the years, their slow speed and undeniable charm have made them victims of human-driven land use change and collection. Their frequent journeys across the landscape also make them common casualties along roadsides where our desire for fast travel conflicts with their slow pace. In many cases, mortality from these sources, particularly roads, far outpaces this long-lived species’ reproduction rate, making it difficult for populations to recover.

If you are interested in learning more about how you can help Wood Turtles, visit the Vermont Fish and Wildlife website. If you want to learn more about Wood Turtles, listen to this episode of Outdoor Radio or read this article from the Orianne Society. And remember to share sightings with the Vermont Atlas of Life on iNaturalist—all locations are automatically obscured, so rest assured that you can safely share your discoveries and contribute to Wood Turtle monitoring in Vermont.

 

Photo 1: https://www.inaturalist.org/observations/18358871

Twice-stabbed Lady Beetle (Chilocorus stigma) on an American Beech trunk. K.P. McFarland licensed under CC-BY-NC
Twice-stabbed Lady Beetle (Chilocorus stigma) on an American Beech trunk. K.P. McFarland licensed under CC-BY-NC

Life at the Beech

By Kent McFarland

It is hard to walk through the forest without noticing the pocked trunks of American Beech (Fagus grandifolia) trees. A mature tree with smooth gray bark is a rare sight now. The culprit is beech bark disease. It’s caused by a unique relationship between an introduced insect called the Beech Bark Scale (Cryptococcus fagisuga), and Nectria fungi (Nectria coccinea var. faginata and N. galligena). This disease has been known in Europe since at least the 1840s, where it attacks European Beech (F. sylvatica). It was accidentally introduced to North American at Halifax, Nova Scotia, in 1890, on a shipment of ornamental trees.

The infestation spreads about 10 miles per year, mainly from the dispersal of Beech Bark Scale by wind and animals. It first appeared in New England in 1929 when it was found in Maine. By 1950 it was found throughout the entire state, and by 1960 it was found across New England. Today it is as far west as Wisconsin and south into North Carolina and Tennessee.

Carefully examine a few beech trunks and you’re likely to find the native Twice-stabbed Lady Beetle (Chilocorus stigma), aptly named for the two bright red spots on each side of its black elytra, feeding on Beech Bark Scale. Here in the north, overwintering adults become active in early spring (April) when mating begins. They lay eggs soon after mating and the larvae emerge in late May. They feed and undergo four instars before pupating. The adults that overwintered will continue to feed through June and early July. Their young mature in early to mid July, and then they mate and lay eggs. Finally, second generation larvae are observed beginning in mid July through early August. These second generation adults emerge in late summer and early fall and overwinter in ground litter.

Beech Bark Scale is easy to see on infected trees. They exude small but noticeable white, waxy filaments on tree trunks. These wingless insects are parthenogenetic, egg growth and development occurs without fertilization by a male and all offspring are females. Adults lay eggs in the summer which soon hatch and the young nymphs, called crawlers, move into bark fissures or may be carried to other trees by wind or wildlife. Once the young crawlers settle down they push their stylet, a sharp needle-like mouthpart, into the bark and begin feeding and secreting the woolly wax cover that they use to help survive the winter season.

The minute wounds created by the stylets allow Nectria fungi to colonize. The fungal colonies cause cankers on the bark surface. This quickly leads to wilting of leaves and loss of twigs and branches. Eventually, the cankers cause enough damage around the tree that the trunk simply snaps in a windstorm. Beech snap is now common throughout the New England forest.

This is bad news for a tiny blue butterfly called the Early Hairstreak (Erora laeta). Its caterpillars feed on the developing fruits of beech trees or hazelnut shrubs. They first feed on the seed husks, then the bore into the husk and eat the soft young nuts. Several nuts may be required for a larva to mature. Early Hairstreak populations seem to fluctuate from year to year, probably in response to beech nut production.

Early Hairstreak (Erora laeta) on a gravel road. K.P. McFarland licensed under CC-BY-NC
Early Hairstreak (Erora laeta) on a gravel road. K.P. McFarland licensed under CC-BY-NC

As its name implies, it is the earliest flying hairstreak in Vermont, found in May and June. Its infrequent encounters in Vermont, and elsewhere, may be because it breeds in the canopy of American Beech, making it difficult to find. It has been known to visit dirt roads and nectar sources near stands of its host plant.

There is at least a glimmer of hope. Some resistant trees have been found and are now being produced in nurseries with the hope that they could be transplanted throughout the range to perhaps bring healthy beech slowly back to the forest one day.

Add your lady beetle sightings to the Vermont Lady Beetle Atlas and Early Hairsteak discoveries to e-Butterfly.org and help us to better understand these insect populations.

 

Photo 1: https://www.inaturalist.org/observations/47652960
Photo 2: https://www.inaturalist.org/observations/36335720

Common Loon (Gavia immer) © Susan Elliott licensed under CC-BY-NC
Common Loon (Gavia immer) © Susan Elliott licensed under CC-BY-NC

Loon Language

By Kent McFarland

Perhaps one of the most fascinating things about loons is their haunting and variable voice.  Loons are most vocal from mid-May through June.  They have four distinct calls which they use to communicate with their families and other loons.

The Mournful “Wail” – An “ooohh ahhhh” is often the sounds of loons identifying or calling to each other; it can also signal initial signs of a mild disturbance.

 

The Laughing “Tremolo” – A trill or series of trills can be a sign of distress or alarm, and occasionally excitement.

 

The Crazy and Wild “Yodel” – This is the male territorial call, usually directed at unwelcome loons. Every male has a distinct yodel and transmits much information through the yodel – from how big the male is to his motivation to defend.

 

Hoots and Coos – On a quiet evening you can hear the loon family or group of loons in a “social gathering” communicating to each other.

 

Listen for loons and be sure to report your sightings to Vermont eBird, a project of the Vermont Atlas of Life, and help us track their populations.

 

Photo 1: https://www.inaturalist.org/observations/27789234

Spurred Carpenter Bee (Ceratina calcarata) © Spencer Hardy licensed under CC-BY-NC
Spurred Carpenter Bee (Ceratina calcarata) © Spencer Hardy licensed under CC-BY-NC

Small Carpenter Bees

By Spencer Hardy

If you live in the Champlain Valley and have untreated wood on your property or have spent time further south in the US, you might be familiar with Large Carpenter Bees (Xylocopa)—they are loud, aggressive, and like to drill holes in houses, barns, and fence posts. Small Carpenter Bees (Ceratina) on the other hand are tiny and unobtrusive but ubiquitous. A large portion of the small dark bees flying right now belong to this group, and although they are small, they have a relatively distinctive shape and can be recognized with practice. The body is a dull metallic blue and relatively hairless and the abdomen is swollen towards the rear unlike other small bees. Males have a horizontal white stripe across the lower portion of the face whereas females usually have a vertical white mark in the middle of the face.

As far as we know, Vermont has 3 species that are all relatively widespread and common. Only males of the Spurred Carpenter Bee (C. calcarata) are likely to be identifiable from photos, though a 4th species—the Nimble Carpenter Bee (C. strenua)—has a long, white line on the front legs that is distinctive among females. This species is known from as far north as western Massachusetts and may exist somewhere in Vermont too.

If you come across any of these Carpenter Bee species, make sure to share your sighting with the Vermont Atlas of Life on iNaturalist!

 

Photo 1: https://www.inaturalist.org/observations/44887571

Eastern White Pine (Pinus strobus) can grow to be over 200 feet tall. © Susan Elliott licensed under CC-BY-NC
Eastern White Pine (Pinus strobus) can grow to be over 200 feet tall. © Susan Elliott licensed under CC-BY-NC

Meat Eating Trees

By Kent McFarland

Plants are not often thought of as predators. They’re the nice guys. With over 300,000 species known to exist, only a small fraction are known to be meat-eaters. In our northern bogs, for example, insects are trapped on the sticky hairs of sundew or drowned in the pitcher plant’s water.

Research now suggests that at least one tree may owe its size to more than just sun, water and good soils.

The Eastern White Pine is one of the tallest native tree species in our region. Give them a few hundred years in ideal floodplain habitat, with roots sunk deep into sandy and silty soils and protected from winds and lightning by hillsides, and they’ll grow to over 200 feet tall with nearly eight foot diameter trunks.

It takes a lot of energy and nutrients for a tree to grow to such grandeur. One thing that might help the eastern white pine is its surprising relationship with a meat-eating fungus.

The Bicolored Deceiver (Laccaria bicolor) appears above ground as a small, tan mushroom with lilac-colored gills. It is found in most coniferous woodlands throughout temperate regions around the globe. The fungus has a symbiotic relationship with many trees, including the eastern white pine. It forms a mycorrhizal sheath, like roots of the fungus, around the small root tips of the tree. The fungus receives sugars from the tree’s photosynthesis that takes place above ground, while it supplies the plant with essential nutrients and helps to increase water uptake by the tree roots from below ground.

Such symbiotic relationships between trees and fungi are common. About ninety-five percent of plants get some nutrients from fungi, and fungi play a critical role in the food web. In particular, fungi (along with lightning strikes and soil bacteria) are critical for converting atmospheric nitrogen into reactive forms, such as nitrate and ammonia, which other living things can use for growth.

What makes the Eastern White Pine’s relationship with the bicolored deceiver surprising is the way the tree benefits from the fungus’ meat-eating habits. This discovery occurred by accident, during a study of tiny soil arthropods called springtails.

Many observers know springtails as snow fleas, the wingless insects often seen by the thousands jumping across the snow in late winter. They are incredibly small, but they can occur in huge numbers. Soil ecologists John Klironomos, now at the University of British Columbia, and his colleague Miranda Hart, wondered if springtails had an adverse effect on trees since they ate fungi that helped secure nutrients for many plants. They set up a simple experiment to feed the springtails a diet of fungi, including bicolored deceiver.

That’s when their experiment took a strange turn. All of the springtails died when they were with bicolor deceiver. “It was as shocking as putting a pizza in front of a person and having the pizza eat the person instead of vice versa,” Klironomos told Science News.

To confirm their findings, Klironomos and Hart fed a few hundred springtails a diet of bicolor deceiver while others were fed a diet either devoid of the fungus altogether or with another fungi species. After two weeks, only five percent of the springtails that were with bicolor deceiver remained alive. In contrast, nearly all the springtails that ate other species of fungi or whose diet was devoid of fungi survived.

The fungus was killing the springtails and breaking them down with a special enzyme. The researchers believe that the fungus first paralyzes the springtails with a toxin and then extends fine filaments into them to absorb nutrients.

So how does this make the Eastern White Pine tree a meat-eater? As a follow up experiment, Klironomos and Hart fed a batch of springtails a diet with nitrogen that was tagged radioactively so they could follow it through the food web. The insects were added to containers of bicolor deceiver growing with white pine seedlings. After a few months they tested the seedlings and found that 25% of the nitrogen in the trees was radioactive, and thus had come directly from the springtails. It’s as if white pine were fishermen using the fungus like a giant net to capture their prey.

Research from scientists at Brock University in Ontario suggests that this adaptation may be shared by many plants. Green muscardine fungus, a soil-dwelling fungus found in many ecosystems, has long been known to infect insects. It has now been shown to associate with plant roots and transfer nitrogen from its insect prey to grass and even beans.

With webs of mycelia hunting tiny prey underground to help giants grow and capture the sun above, understanding who is eating whom just got a lot more complicated.

 

Photo 1: https://www.inaturalist.org/observations/717388

Comments (1)

  1. D.moss. says:

    Always learning from you folks
    Hope ecology of the woods
    Becomes required for highs coolers
    Thanks again

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