The Mist, the Meadow, and a Mystery

The weather this winter has been very variable, with warm temperatures and foggy conditions one day, followed by cold, wind and snow the next.  On one of the recent warm foggy days, I went for a walk at Bowman’s Hill Wildflower Preserve, just south of New Hope, Pennsylvania.  The misty air exaggerated everything – silence, sounds, colors and images.

Fog in the woods

Fog in the woods

Soft light intensified the bright white and green of the Lumpy Bracket (Trametes gibbosa) mushroom, causing it to jump out and catch my eye.

Lumpy Bracket (Trametes gibbosa)

Lumpy Bracket (Trametes gibbosa)

The changeable weather makes it challenging to adjust to the season, not just for people, but for plants, too.  I saw Golden Alexanders (Zizea aurea) in bud, a plant that typically blooms in early May in this area in eastern Pennsylvania.  A little scary!

Golden Alexanders (Zizia aurea)

Golden Alexanders (Zizia aurea)

Two White Ash (Fraxinus americana) trees were sentinels on the approach to the meadow…

White Ash (Fraxinus americana) trees at the edge of the meadow

White Ash (Fraxinus americana) trees at the edge of the meadow

…where the grasses were beaded with water droplets.

Switchgrass (Panicum virgatum)

Switchgrass (Panicum virgatum)

Purpletop (Tridens flavus)

Indiangrass (Sorghastrum nutans)

Indiangrass (Sorghastrum nutans)

There were many signs of life in the meadow. A spider successfully blended in with the dried fruit capsules of Culver’s Root (Veronicastrum virginicum).

Culver’s Root (Veronicastrum virginicum) with spider

Culver’s Root (Veronicastrum virginicum) with spider

Spider on Culver’s Root (Veronicastrum virginicum)

 Chinese Mantis (Tenodera aridofolia sinensis) egg cases were very common.

Chinese Mantis egg case on Indian-hemp (Apocynum cannabinum) fruit capsules

Chinese Mantis egg case on Indian-hemp (Apocynum cannabinum) fruit capsules

Much less common was the egg case of a native, the Carolina Mantis (Stagmomantis carolina). I only found one.

Carolina Mantis (Stagmomantis carolina) egg case

Carolina Mantis (Stagmomantis carolina) egg case

The mantises are pretty indiscriminate about where they deposit their egg cases. They are not plant specific, but will use any sturdy structure that’s handy – a shrub, a perennial, even a fence will do.  Each egg case, or ootheca, may contain hundreds of eggs.  The young will all emerge at the same time in the spring. (Unless they’re eaten by another insect first!)

Goldenrod galls were evidence of insects overwintering. A gall is a growth that is a plant’s reaction to being used, or colonized, by another organism.  Galls generally don’t cause any harm to the plant.

Goldenrod Ball Gall

Goldenrod Ball Gall

One of the easiest galls to recognize is the goldenrod ball gall, a spherical growth found on the stems of some goldenrods, caused by the goldenrod gall fly (Eurosta solidaginis), a fruit fly. There are many species of goldenrod, but the goldenrod gall fly is very particular about which species it will use;  it specializes primarily on Solidago altissima, but Solidago giantea may also be a host. (Solidago altissima goes by many common names: the USDA calls it Canada Goldenrod, but other sources may use Tall or Late Goldenrod. Solidago giantea is Giant Goldenrod according to the USDA, but it is referred to by other sources as Late or Smooth Goldenrod. So confusing! This makes the need for a standard scientific name clear.)

The adult female goldenrod gall fly lays an egg in the leaf bud of the goldenrod before the leaves unfold. After hatching, the larva bores into the stem of the plant, and begins to eat. This stimulates the plant to generate additional nutrients and the gall tissue, a process that takes about three weeks to complete. The gall provides food and shelter for the insect for the remainder of its stay.  After spending the winter in a dormant state, called diapause, if the insect is lucky it will pupate in spring and then emerge as an adult from its winter home.

But there are many dangers that could cut the life of the goldenrod gall fly larva short while it takes shelter in the gall. Other insects, including two chalcid wasp species, Eurytoma gigantea and Eurytoma obtusiventris, may eat the insect larva and take possession of the gall. If the goldenrod gall fly larva manages to avoid these and other predators, a Downy Woodpecker or a Chickadee may make it a tasty winter meal.

This Goldenrod Ball Gall has been excavated by a Downy Woodpecker

This Goldenrod Ball Gall has been excavated by a Downy Woodpecker

The goldenrod bunch gall resembles a flower, but it is actually a rosette of leaves caused by the entry of a goldenrod bunch gall midge (Rhopalomyia solidaginis) larva into the stem of its host goldenrod species, Solidago altissima. This stops additional upward growth in the stem of the plant, although leaves will continue to sprout, forming the rosette.  Additional growth is through side shoots branching off from the stem below the gall.  The presence of this gall actually increases the diversity of other insect species where it is present, by providing additional habitat for them.

Goldenrod Bunch Gall

Goldenrod Bunch Gall

I found a wonderful, complex, twisted, origami-like structure made in the leaves of Indiangrass (Sorghastrum nutans) that remains a mystery to me.

Mystery shelter

Mystery shelter

Could it be a winter shelter for a butterfly caterpillar, maybe a Pepper and Salt Skipper?  This butterfly is possible, although not common in this area, and its caterpillars spend the winter in rolled grass leaves, including Indiangrass.  Maybe some other skipper?  Or did a spider make this refuge? If you have any idea who could be hiding inside, let me know!

If you are lucky enough to have custody of a meadow, you may be wondering how to maintain it without killing the critters that live there. To prevent a meadow from evolving into a forest, you will have to mow it. But this will disrupt habitat for the resident insects, birds and mammals. To minimize the damage, try mowing at a height of 12-16 inches, in a mosaic pattern if possible, and don’t mow more than a third of the meadow in a year. For the sake of birds and mammals, mow as late in the winter as you can. These techniques will help preserve life, and increase the diversity of the residents in your meadow.

Chipping Sparrow on Indiangrass

Chipping Sparrow on Indiangrass

Resources

Eastman, John. The Book of Field and Roadside. 2003.

Eiseman, Charley; Charney, Noah. Tracks & Sign of Insects and Other Invertebrates. 2010.

Mader, Eric; Shepherd, Matthew; Vaughan, Mace; Black, Scott Hoffman; LeBuhn, Gretchen. Attracting Native Pollinators: Protecting North America’s Bees and Butterflies. 2011.

Special thanks to Beatriz Moisset, who was generous with information about goldenrod galls, including pointing me to some helpful information on Bugguide.net: http://bugguide.net/node/view/324012

I found this paper especially interesting: Host-plant Genotypic Diversity Mediates the Distribution of an Ecosystem Engineer, by Kerri M. Crawford, Gregory M. Crutsinger, and Nathan J. Sanders

Pipevine Swallowtail Butterflies and Their Host, Dutchman’s Pipevine

Late one afternoon a pair of dazzling creatures caught my eye as I walked toward my car in the parking lot at Bowman’s Hill Wildflower Preserve.  They were Pipevine Swallowtail butterflies, a male and a female, flitting about in the neighborhood of a very large Dutchman’s Pipevine (Aristolochia macrophylla), the plant that gives them their name.

As I watched, the female occasionally landed on the Dutchman’s Pipevine, staying in one spot for a few moments, with her lower abdomen curved slightly to touch the Pipevine leaves or stems.  She was laying eggs!  In the photo below, two roundish orange eggs are visible on the stem of the vine, next to her right front leg.  If you look carefully at the tip of her abdomen, you can see a spot of orange – she’s just about to lay another.

Pipevine Swallowtail Butterfly laying eggs on Dutchman’s Pipevine

Some butterflies have evolved a survival strategy that enables their caterpillars to feed on a wide variety of plants, but others, like the Pipevine Swallowtail, have chosen to specialize on a small number of plants that give them a particular advantage.  To protect itself from being eaten, Dutchman’s Pipevine has evolved with chemicals that are at minimum distasteful to those who would eat it, and if a sufficient amount is ingested, they are toxic.  Pipevine Swallowtail caterpillars are among the few creatures who are able to process these chemicals without harm to themselves, then store them in their bodies in such a way that they are toxic to their potential predators.  This chemical protection even survives metamorphosis and extends to the adult butterfly.  It is so effective that other butterflies mimic the appearance of the Pipevine Swallowtail, since this is often enough to warn off predators.

Pipevine Swallowtails lay their eggs in small clusters of usually less than twenty, often on young leaves or stems of Pipevine plants, members of the genus Aristolochia.  In the mid-Atlantic, the only species that Pipevine Swallowtail caterpillars can eat are Dutchman’s Pipevine and Virginia Snakeroot.  In the southwestern part of its range, there are other native Pipevine species that this butterfly uses as its caterpillar food plants.

Pipevine Swallowtail Eggs on Dutchman’s Pipevine

Soon after they hatch, the young caterpillars have a reddish spiny appearance. They tend to feed together in groups.

Young Pipevine Swallowtail Caterpillars

Older caterpillars usually feed alone, and their appearance changes, with colors appropriate for Halloween – black with orange trim.

Pipevine Swallowtail Caterpillar on Dutchman’s Pipevine

Adult butterflies feed on a variety of plants for their nectar, and may also seek out minerals at puddles.  They don’t feed on the flowers of the Pipevines, however, because they are not a good anatomical match for feeding or pollination.

Dutchman’s Pipevine is a deciduous vine with large heart-shaped leaves, but it is named for the shape of its flowers, which have a curved tubular shape ending in a flair with an opening in the center to allow pollinators to enter and search for a nectar reward.  The graceful Pipevine Swallowtail is too large to enter, and even its proboscis can’t extend enough to navigate the long curved tube to reach the flower’s food offerings.

Dutchman’s Pipevine Flower in bloom

So how are the Pipevine flowers pollinated?  Small flies and gnats are attracted to the open throat of the flower by an aroma they can detect, and by the color pattern, both directing them forward down the tube.  As the insects enter, they are prevented from reversing course by hairs that line the flower’s throat, forcing the insect forward, a little like the metal spikes at parking lot entrances that will puncture your tires if you back up.  When the insect reaches the nectar source, it meets the sticky stigma of the female flower parts, depositing pollen brought in on its body from another Pipevine flower.  The plant detains the insect until the flower has been fertilized, offering it shelter and nectar, sort of like a little insect bed and breakfast.  The female flower parts wither, and the male parts mature, releasing pollen for the insect to pick up on its body.  The flower tube and its hairs relax enough for the insect to escape the way it entered, taking the pollen to the next flower it visits, ensuring the continuation of both the Dutchman’s Pipevine and the Pipevine Swallowtail species.

Dutchmans Pipevine on fence at Bowman’s Hill Wildflower Preserve