Downy Skullcap and the Amorous Skippers

Apparently I planted some Downy Skullcap (Scutellaria incana) in our garden last year and then promptly forgot, so it was a delightful surprise when the vivid blue flowers began to bloom in long stalks above gray-green foliage.

Downy Skullcap (Scutellaria incana) with Flower (Syrphid) Fly

Downy Skullcap (Scutellaria incana) with Flower (Syrphid) Fly

Each long tubular flower has an entrance with a hood- or cap-like overhang at the top, and a floor with a white pathway beckoning to visitors who might help pollinate the flowers.

Downy Skullcap (Scutellaria incana) Flower

Downy Skullcap (Scutellaria incana) Flower

The almost sapphire blue flowers are especially attractive to bees, and are thought to be most often pollinated by Bumble Bees (Bombus species) but they entice other pollinators as well, including flower flies, bee flies, and small butterflies.

I watched for visitors to the flowers in our garden and at another near-by site, Bowman’s Hill Wildflower Preserve. At both locations, bees were the most frequent visitors on days when I checked, and of the bees, Small Carpenter Bees (Ceratina species) were the most common.

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species)

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species)

Don’t be put off by the fact that they are called carpenter bees.  These tiny bees won’t be drilling holes in the deck, siding or wood trim of your home.  They nest in the stems of dead or broken twigs, excavating nesting cells by chewing through the pith, the softer tissue inside the stem.  Small Carpenter Bees are pollinators of many plants, especially those with small flowers.

Each bee crawled inside the flower, disappearing down the throat until they reached the nectar reward at the bottom.

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) crawling down the throat of the flower to reach the nectar reward

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) crawling down the throat of the flower to reach the nectar reward

But it wasn’t just nectar they were after.  Bees need a balanced diet.  They wanted pollen, too, for the protein and lipids it provides.  The flowers’ reproductive parts, the stamens and pistils, are hidden under the hood at their entrance.  After emerging from drinking nectar at the depths of a flower, each bee then checked under the hood for pollen, which is dispersed from the anthers at the stamens’ tips.  Some bees even went straight for the pollen without bothering with the nectar.  Hopefully some of that pollen was later deposited on the stigma of another flower, the female flower part where pollen must be placed in order for pollination to occur.

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) emerging from the flower

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) emerging from the flower

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) harvesting pollen

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species) harvesting pollen

Much larger relatives of these tiny bees, Eastern Carpenter Bees (Xylocopa virginica), also visited the flowers.  Although these bees can be excellent pollinators, it pains me to tell you that in the case of Downy Skullcap, Eastern Carpenter Bees are thieves. They can’t access the flowers’ nectar by going through the inviting entrance, thus interacting with the flowers’ reproductive parts and helping with pollination.  So instead, they bite through the floral tube near its base, directly accessing the nectar, doing nothing in return to assist the plant in its reproductive goals.  Interestingly, a Honey Bee tried to discourage the Eastern Carpenter Bees from this dishonest activity by trying to chase them away, with some success. And yes, regrettably, Eastern Carpenter Bees might choose to nest in the wood of your home.

Downy Skullcap (Scutellaria incana) with Eastern Carpenter Bees (Xylocopa virginica) robbing the flower of nectar by biting through the floral tube to drink it.

Downy Skullcap (Scutellaria incana) with Eastern Carpenter Bees (Xylocopa virginica) robbing the flower of nectar by biting through the floral tube to drink it.

While looking for Downy Skullcap flower visitors in our garden, I spotted a male Zabulon Skipper drinking nectar.

Male Zabulon Skipper drinking nectar from a Downy Skullcap (Scutellaria incana) flower

Male Zabulon Skipper drinking nectar from a Downy Skullcap (Scutellaria incana) flower

A moment later, I noticed a female Zabulon Skipper, doing the same.

Female Zabulon Skipper drinking nectar from a Downy Skullcap (Scutellaria incana) flower. Notice the bee disappearing into the flower above hers.

Female Zabulon Skipper drinking nectar from a Downy Skullcap (Scutellaria incana) flower. Notice the bee disappearing into the flower above hers.

Then the male flew over to the female and suggested a ‘hook up’.

Female (top) and male (bottom) Zabulon Skippers, negotiating a hook up. Their wings are a little out of focus because both were vibrating them energetically as a lead up to an agreement.

Female (top) and male (bottom) Zabulon Skippers, negotiating a hook up. Their wings are a little out of focus because both were vibrating them energetically as a lead-up to an agreement.

She was apparently persuaded by his pitch.  They went off to a more secluded spot, and stayed there beyond the limits of my attention span.

Zabulon Skippers, mating

Zabulon Skippers, mating

Zabulon Skippers, mating

Zabulon Skippers, mating

These small butterflies are common in gardens and natural areas, specializing on many grass species as food for their caterpillars, including Purpletop (Tridens flavus), Purple Love Grass (Eragrostis spectabilis), and other related species.

Purpletop (Tridens flavus), a caterpillar food for Zabulon Skippers

Purpletop (Tridens flavus), a caterpillar food for Zabulon Skippers

When the flowers have finished blooming and drop away, a cap-shaped calyx, the set of sepals that act as bud scales remains, providing the inspiration for the common name ‘skullcap’.

Cap or dish like calyxes of Downy Skullcap (Scutellaria incana)

Cap- or dish-like calyxes of Downy Skullcap (Scutellaria incana)

‘Downy’ in the common name and ‘incana’ in the scientific name, which means hoary or quite gray, refer to the short soft hairs present on the flowers and stems of this plant. Hoary Skullcap is another common name for the species.

Downy Skullcap is native in the United States from New York west to Wisconsin, south as far as Texas and the Florida panhandle.  It can tolerate full sun to full shade, dry to moist soil. Blooming in mid-summer, it makes a dramatic addition to a garden.  Add it to yours and wait for the real drama (food foraging, bee face-offs, theft, flirtation, sex!) to begin.

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species)

Downy Skullcap (Scutellaria incana) with Small Carpenter Bee (Ceratina species)

Resources

Cech, Rick; Tudor, Guy.  Butterflies of the East Coast.  2005.

Eaton, Eric R.; Kauffman, Ken.  Kaufman Field Guide to Insects of North America.  2007.

Rhoads, Ann Fowler; Block, Timothy A.  The Plants of Pennsylvania.  2007

Stearn, William T. Stearn’s Dictionary of Plant Names.  1996

Willmer, Pat.  Pollination and Floral Ecology. 2011

Wilson, Joseph S.; Carril, Olivia Messinger.  The Bees in Your Backyard. 2016.

Illinois Wildflowers

Lady Bird Johnson Wildflower Center Plant Database

Missouri Botanical Garden Plant Finder

USDA NRCS Plants Database

 

The Artistry of Seedbox

Winter is the perfect time to see Seedbox (Ludwigia alternifolia) in fruit, and to understand how this plant got its name.

Seedbox (Ludwigia alternifolia) with fruit capsules

Attached along the length of the standing stems of this plant are fruit capsules that look like perfectly carved wooden boxes, each with a convex top and rounded bottom, and with elaborate designs that appear to be carved on the cube’s lid.

Seedbox (Ludwigia alternifolia) fruit capsules

These tiny decorative fruit capsules are often visible throughout winter, splitting open at the seams when ripe to release the many tiny seeds inside.  Before the fruit capsule opens, the seeds may rattle, giving this plant another common name, Rattlebox.

How is this perfectly shaped fruit capsule produced?  Who is responsible for the beautiful carvings on the lid? (Could it be tiny flower elves?  Maybe there is a less magical explanation.)

Seedbox typically blooms in mid to late summer, usually July and August.  Let’s look at the flowers and buds for an explanation.

Seedbox (Ludwigia alternifolia) in bloom

In Seedbox buds, sepals are the outermost layer of flower parts. They are green and leaf-like, and play the role of bud scales, enclosing and protecting the other parts of the flower before it opens.  The photo below shows a flower bud, enclosed by the sepals. In the upper right of the photo, there is a notch in the sepals at the base of the bud, a narrowing of the structure, and a squarish impression in the leafy covering.  This covering is enclosing the flower’s ovary, the flower part destined to become the fruit capsule.  We can see two sides of the ovary, already hinting at the box-like fruit capsule to come.

Seedbox (Ludwigia alternifolia) flower bud. In the top right corner, note the square ovary with a leafy covering at the base of the bud. The ovary will become the fruit capsule; its square shape is already in place.

The purpose of the flowers is to attract visitors to assist with cross-pollination. The most effective pollinator will have a tongue long enough to reach the nectaries on the face of the ovary below, while brushing its body on the flower’s reproductive parts, including the Sweat Bee in the photo below, and some Bumble Bees.  Other bees and beetles are known to visit the flowers for nectar and pollen, while flies, wasps, and butterflies only partake of the nectar.

Seedbox (Ludwigia alternifolia) flower with a visiting Sweat Bee. Her tongue is long enough to reach the nectaries while her body brushes against the flower’s reproductive parts, dropping off and picking up pollen.

The bee is rewarded for her pollination assistance with nectar and pollen for herself, and she will also carry some back to provision her nest for her larvae.

Seedbox (Ludwigia alternifolia) flower with a visiting Sweat Bee. Notice the pollen she has packed on her hind legs to bring back to her nest for her larvae.

Let’s look at an open flower.

Seedbox (Ludwigia alternifolia) in flower.

Working from the outer ring of flower parts layer by layer towards the center, each flower has four sepals, four yellow petals, four stamens (male reproductive parts) and one pistil (female reproductive part).  The pistil consists of a stigma at its tip, where the pollen must be deposited in order for pollination to take place, the style, which positions the stigma and through which the pollen must travel to get to the ovary, which is at the pistil’s base. Seedbox stigmas look like miniature pompoms perched at the top of their pedestal-like styles.  As the ovary ripens to a fruit capsule, if the pollen successfully reaches and fertilizes the ovules in the ovary, seeds will be produced.

Seedbox (Ludwigia alternifolia) in flower. The green sepals are peeking out from behind the yellow petals. The petals, stamens and style of the pistil are attached to the top of the ovary, while the sepals are appressed to the four sides of the ovary.

If we look at the very center of the flower, we can see the petals, stamens and pistil attached to the square top of the ovary, with the sepals appressed to the four straight sides around the ovary’s outside edges.

The flower parts that made pollination possible eventually wither and drop off, leaving their mark on the face of the ripening fruit capsule.

The petals drop off after about a day, leaving tiny scars that can be seen at each corner of the developing fruit capsule’s topside.  As the stamens drop off, each leaves a mark midway between the corners, just slightly in from the edge of the square.

Developing Seedbox (Ludwigia alternifolia) fruit capsule. Notice the scars left by the petals and stamens which have withered and dropped off. The stigma, style and sepals are still present.

Eventually the pistil’s stigma and style, positioned at the center of the flower above the ovary, drop off, leaving a round scar as a reminder of their role in the flower’s reproduction strategy.

Developing Seedbox (Ludwigia alternifolia) fruit capsule. The stigma and style have dropped off. The sepals are still present.

Finally the sepals are gone, leaving the bare woody ‘seedbox’.

Seedbox (Ludwigia alternifolia) fruit capsules

The face of a Seedbox fruit capsule records the history of its pollination story. The four large-ish evenly spaced ovals in each quadrant on the top of the fruit capsule were the nectaries, the source of the beverage that enticed the flower’s visitors.

Seedbox (Ludwigia alternifolia) fruit capsules. The scars from the petals and stamens are visible near the edges of the fruit capsule’s top, the round scar in the center marks the spot where the style was attached, and the four ovals are the flower’s nectaries.

Seedbox prefers moist soil, and can be found growing in wet meadows, prairies and woods, as well as in drainage ditches. It is native in Quebec and Ontario provinces in Canada, and in the United States from Vermont west to Wisconsin, southwest to Colorado, then south as far as Texas and the Florida panhandle. It is a member of the Evening-primrose (Onagraceae) family.

If you’re looking for something to do while waiting for spring, look for Seedbox!

Dedication:  Pam, this is for you!

Related Posts

Evening Primrose

Resources

Illinois Wildflowers

Illinois Wildflowers Flower Visiting Insects

Missouri Botanical Garden

USDA NRCS Plant Database

 

 

Holiday Gift Ideas for Your Wild Neighbors

American Robin with Winterberry Holly (Ilex verticillata) at Bowman’s Hill Wildflower Preserve, New Hope, PA

Looking for the perfect holiday gifts for the birds, butterflies, bees and other wildlife neighbors outside your windows?

The answer is simple.  Give them plants that are native to where you live.  Plants and animals have evolved together over many centuries in such a way that they depend on each other for their survival.  Animals depend on native plants for food, shelter, nesting sites and materials.  Plants in turn depend on animals to help disperse their seeds, and in many cases for essential assistance in reproduction, as their pollination intermediaries.

You’ll be doing yourself a favor, too, since native plants, once established, typically don’t require fertilizer, watering or other special care.

The American Robin shown here with Winterberry Holly (Ilex verticillata) was one member of a flock of Robins that swooped down to devour the bright winter-time fruit.  Winterberry Holly has fruit high in carbohydrates and low in fats, a recipe for being ignored during migration season in fall, but devoured during the cold days of winter when birds need those carbohydrates. In exchange for this winter feast, birds ‘disperse’ the seeds complete with fertilizer after the seeds move through a bird’s digestive system.

If you live in North America, here are a few resources to help you learn which plants are native where you live:

Lady Bird Johnson Wildflower Center

Audubon

North American Native Plant Society

Also check with your local state or province native plant society.

For the birds, another great gift idea is a heated bird bath.  Birds need to drink and bathe even in winter.

What else can you do? Less:

  • Leave the fallen leaves in your planting beds.  They provide habitat for overwintering insects, and the insects are food for birds.
  • Don’t use pesticides or herbicides
  • Reduce your lawn size if possible
  • Chop up leaves on your lawn with a mulching mower to create a natural chemical-free fertilizer

Happy holidays!

Related Posts

A Wildlife, Family and Pet-friendly Lawn

Red-banded Hairstreaks Need Sumacs and Leaf Mulch

For Great Spangled Fritillaries, Leave the Leaf Litter

American Robin with Winterberry Holly (Ilex verticillata) at Bowman’s Hill Wildflower Preserve, New Hope, PA

Another Migrating Butterfly, and the Plants that Sustain It

Common Buckeyes have been, well, really common this year.

Common Buckeye drinking nectar from Short-toothed Mountain Mint (Pycnanthemum muticum)

That isn’t the case every year in the areas I frequent near the Delaware River in central New Jersey and eastern Pennsylvania.  Common Buckeyes are not year-round residents this far north. They migrate south in late fall to spend the winter in warmer territories, often as far south as Florida.  In migration they can sometimes be seen in large numbers, often moving along the coast in the eastern United States, or sometimes following river valleys.  They migrate north in spring and early summer, sometimes reaching as far north as southern Canada.  Their numbers vary from year to year in these northern locations, becoming increasingly rare the further north they go.

On warm sunny days even in late October, I am still seeing Common Buckeyes often drinking nectar, mostly from flowers that are members of the Aster family.  This family of plants, which includes asters, goldenrods, sunflowers, bonesets, beggar-ticks, and more are typically the most abundant plants blooming in late summer through the end of the growing season.

Common Buckeye nectaring on Aromatic Aster (Symphyotrichum oblongifolium)

Common Buckeyes can also be found basking at ground level, catching the low rays from the late season sun.

Common Buckeye basking

Common Buckeyes frequent open fields, roadsides, gardens, and even beaches, especially where nectar plants are available.

Common Buckeye drinking nectar from goldenrod flowers along the sandy beach at Cape May, New Jersey

Common Buckeyes have a fairly broad geographic range, and have evolved to use a variety of plants as food for their caterpillars, including plantains, figworts,

Lanceleaf Figwort (Scrophularia lanceolata), a caterpillar food plant for Common Buckeye butterflies

gerardia,

Purple Gerardia or Purple False Foxglove (Agalinis purpurea), a caterpillar food plant for Common Buckeye butterflies

Monkey Flower,

Allegheny Monkey Flower (Mimulus ringens), a caterpillar food plant for Common Buckeye butterflies

and Wild Petunia.

Fringeleaf Wild Petunia (Ruellia humilis) a caterpillar food plant for Common Buckeye butterflies

The coloration of the Common Buckeye’s outside hind wing early in the season is mostly tan, with prominent eye spots.

Common Buckeye drinking nectar from Short-toothed Mountain Mint (Pycnanthemum muticum). Note the tan color and eyespots of the hind wing.

The wing color can be quite different in late summer and fall, taking on a rosy hue.  This may be an adaptation that helps Common Buckeyes blend in with the changing color of the surrounding foliage.

Common Buckeye in autumn. Note the rosy color of the hind wing.

Keep an eye out for Common Buckeyes on these last warm days of fall!

Common Buckeyes on goldenrod

 

Resources

Brock, Jim P.; Kauffman, Ken.  Kaufman Field Guide to Butterflies of North America.  2003.

Cech, Rick; Tudor, Guy.  Butterflies of the East Coast.  2005.

Glassberg, Jeffrey.  A Swift Guide to Butterflies of North America.  2012.

Glassberg, Jeffrey.  Butterflies through Binoculars A Field Guide to Butterflies in the Boston-New York-Washington Region.  1993.

Rhoads, Ann Fowler; Block, Timothy A.  The Plants of Pennsylvania.  2007

Wagner, David L.;  Caterpillars of Eastern North America, 2005.

Canadian Biodiversity Information Facility: Butterflies of Canada

Butterflies and Moths of North America

 

 

Wingstem

There are still pockets of Wingstem (Verbesina alternifolia) in bloom along the Delaware and Raritan Canal in central New Jersey.  This species has been flowering in nearby locations since August.

Wingstem (Verbesina alternifolia) along the Delware and Raritan Canal in central New Jersey

Like so many other plants that bloom in late summer and fall, Wingstem is a member of the prolific Aster (Asteraceae) family, which consists of more than 23,600 species.

Aster family members have a floral display that is a composite of multiple flowers, called a flower head, inflorescence, or capitulum.  What our brain wants to interpret as a single flower is really a group of many flowers, all attached to the same platform, or receptacle.

There are two types of flowers that may be present in the flower head of an aster family member, ray flowers and disk flowers.  Each ‘petal’ we see is an individual ray flower that consists of a single petal.  The other type of flower is a disk flower, whose petals have fused to form a narrow tube.  Many Aster family members have a classic look with both ray and disk flowers, while some have evolved to produce just ray flowers, and others just disk flowers.

Aromatic Aster (Symphyotrichum oblongifolium) is a classic aster family member with both ray and disk flowers. A pair of mating Flower (Syrphid) Flies is visiting.

For many species that produce both ray and disk flowers, the ray flowers are sterile; they don’t have functioning reproductive parts.  Their role is just to look pretty, to be part of an appealing advertisement that attracts pollinators to the disk flowers in the center of the flower head.  It’s the disk flowers that produce pollen and nectar, and where the business of reproduction is carried out.

Wingstem is a species that has sterile ray flowers and fertile disk flowers, all attached to a rounded receptacle.  The disk flowers are large and distinct; it’s easy to see each individual flower, especially when insects are foraging for food.

Wingstem (Verbesina alternifolia) flowers with foraging bees. Notice the large but narrow tubular disk flowers projecting from the round recepticle, with the petal-like ray flowers below.

Like its relatives, Wingstem is a great source of food for late season pollinators. The ray flowers open first as a signal to pollinators that the flower head is open for business.  The disk flowers bloom a few at a time, starting with those closest to the ray flowers, then over many days gradually working towards the center of the head.  In each disk flower, the male reproductive parts (stamens) mature first, opening their anthers to make pollen available. Later the female reproductive parts (pistils) replace the stamens, the stigmas at the tips of the pistils becoming receptive to pollen.  At any time while in bloom there may be some flowers in a head that are in the male phase, others in the female phase.

Wingstem (Verbesina alternifolia) with foraging Bumble Bee. Note the distinct disk flowers. Those with a straight brown projection (the anthers) emerging are in the male phase. The disk flowers with yellow curliques (the stigmas) are in the female phase.

It’s easy to see how the pollen-covered Bumble Bee in the photo below would be an effective pollination partner for Wingstem.

Wingstem (Verbesina alternifolia) with foraging Bumble Bee

Not all pollen is destined to be used for pollination, however, since it’s an importance source of food for bees and flies.  Bees and flies drink nectar, but they also eat pollen.  Female bees also collect pollen to bring back to their nests to feed their larvae.  The female below already has a good quantity of food to bring to her offspring, packed onto the bristly hairs on her hind legs.

Female Bumble Bee on Wingstem (Verbesina alternifolia) foraging for food for herself and her offspring. The orange blob on her hind leg is pollen and nectar that she has already gathered to bring back to her nest. Note the long hairs on that leg, perfectly suited to transporting this food.

Sweat Bees and Small Carpenter Bees also visit Wingstem flowers for the nectar and pollen banquet they provide.

Wingstem (Verbesina alternifolia) with visiting Sweat Bee

Small Carpenter Bee on Wingstem (Verbesina alternifolia)

This Toxomerous geminatus, a Flower Fly, may not have a tongue long enough to reach the nectar, but it can still consume pollen from these abundant flowers.

Toxomerous geminatus, a Flower Fly, eating pollen from a Wingstem (Verbesina alternifolia) disk flower

Wingstem nectar is a welcome offering for butterflies.

Summer Azure butterfly drinking nectar from a Wingstem (Verbesina alternifolia) disk flower

Even this thread-waisted wasp is doing her best to get into the flowers to drink nectar.

Mating Thread-waisted Wasps, with female attempting to drink nectar from Wingstem (Verbesina alternifolia) flowers

If these insects assist in transporting pollen to help achieve successful pollination, the disk flowers will produce dry, winged fruits (achenes) that will take the place of the flowers on the globe-shaped receptacle.  The fruits may drop in place, be scattered by wind, or dispersed with the assistance of a passing animal hooked by the pointy bristles on each achene.

Wingstem (Verbesina alternifolia) with fruit still attached to the round recepticle

Deer and other mammals avoid eating Wingstem because of its bitter taste. But there are some insects that happily get nourishment from this species.  The caterpillars of Silvery Checkerspot butterflies and some moths eat Wingstem leaves.

A Yellow Bear moth caterpillar taking refuge in a Wingstem (Verbesina alternifolia) leaf

The aphids in the photo below are feeding on Wingstem sap, while the ants are drinking the aphids’ honeydew (excrement).  The ants will protect the aphids in exchange for this treat.

Aphids on Wingstem (Verbesina alternifolia) flower head, being tended by ants

Wingstem is an herbaceous perennial that often grows to a height of 5-6 feet (1.5-2 meters), but can reach eight feet (2.5 meters) tall.  It can tolerate full sun to part shade, average to moist soil.  This plant’s name describes its appearance, providing clues to its identification.  ‘Wingstem’ refers to the leafy wing-like appendages along the sides of the main stem of the plant.  ‘Verbesina’ means that its foliage is similar to that of verbena, and ‘alternifolia’ tells us that the leaves are alternate, not opposite each other where they attach to the stem.

Note the alternate leaves. The leafy appendages along the sides of the stem, giving this plant its common name, ‘Wingstem’

Wingstem is native in the United States in Massachusetts, Rhode Island, and from New York west to Nebraska, south as far as northeastern Texas and the Florida panhandle.  In Canada, it can be found in Ontario province.  Wingstem is less common in the northern and southernmost parts of its range.

Look for Wingstem and its visitors in late summer and fall.

Wingstem (Verbesina alternifolia) with Bumble Bees

Related Posts

Bountiful Blue Wood Aster

New England Asters – A Hotbed of Activity!

Asters Yield a Treasure Trove

Fall Allergies?  Don’t Blame Goldenrod!

‘Will Work for Food’ – Extra-floral Nectaries

Milkweed – It’s Not Just for Monarchs

Resources

Cech, Rick; Tudor, Guy.  Butterflies of the East Coast.  2005.

Eaton, Eric R.; Kauffman, Ken.  Kaufman Field Guide to Insects of North America.  2007.

Rhoads, Ann Fowler; Block, Timothy A.  The Plants of Pennsylvania.  2007

Stearn, William T. Stearn’s Dictionary of Plant Names.  1996

Wagner, David L.;  Caterpillars of Eastern North America, 2005.

Illinois Wildflowers

Missouri Botanical Garden

USDA NRCS Plant Database