Ramble Report September 6 2018

Today's Ramble was led by Dale Hoyt.

Here's thelink to Don's Facebook album for today's Ramble. (All the photos in this post are compliments of Don.)

Today's post was written by Linda Chafin (plants) and Dale Hoyt (animals).

Today’s Focus: Plants and insects in the lower power line right-of-way.

28 Ramblers met today.

Today's reading: Dale read the August 21 entry from Donald Culross Peatties’ Almanac For Moderns:

NOT blood nor flesh nor hair nor feathers, not the chlorophyll or cellulose of the plants, is stranger than the stuff called chitin. Chitin is not only the hard shell of the dapper little beetles in their tail-coats; it is the glistening wing of the dragon fly, and his thousand faceted eye, the exquisite feathered antenna of the moth by which it perceives the odor of its mate across miles of summer darkness, the feet of the laboring ant, the heavy armor of the lobster, the gossamer of the spider, the thread of the silkworm. There is very little about an insect, or for that matter, any of its allies in the sea or upon the land, which is not chitinous. One moment the stuff is finer than the tresses of woman, and the next ponderous and stiff as the armor of a knight, and all without change in its chemical composition. As a bloom upon the wing of a luna moth fluttering across the moon, it is evanescent as snowflakes; encased in drops of amber where a Mesozoic beetle died, it has seen the ages pass without a change.

Show and Tell:

1. Sue brought two things to show, a wren's nest on top of a bluebird nest, retrieved from a nest box, and a sprig of Fireweed (Pilewort, Erichtites hieraciifolius) with several insect galls on the stem.
2. Carla brought a loofah gourd she grew and shared some of the seeds.
3. Don brought a bit of Hyssopleaf Thoroughwort (Boneset), Eupatorium hyssopifolium, to show. It's in the same genus as the Late Flowering Thoroughwort or Late Boneset, Eupatorium serotinum, that we saw in the ROW last week (and again this week).

Today's Route:   We left the Visitor Center, and headed down the road to the Dunson Native Flora Garden roadside deer fence.  We then worked our way into the lower ROW and explored it to near the river before we called time and headed back the way we came.  We then enjoyed air conditioning, refreshments and conversation at the Cafe Botanica.

LIST OF OBSERVATIONS:

In the round planter next to the bench at the base of the steps leaving the Visitor Center Plaza we found a small caterpillar, probably that of a Painted Lady butterfly.

Caterpillar of Painted Lady butterfly

The pot contained Angelonia angustifolia, sometimes called Summer Snapdragon, a South American plant that is not the commonest host plant for this species. Painted Lady caterpillars usually eat thistles. The caterpillar, when feeding on thistle, builds a messy silken nest that surrounds a few leaves and protects the caterpillar from predatory wasps.

We checked on the Spiranthes odorata in the planter next to the sidewalk to the side entrance of the building.  It's almost fully filled out with its triple spiral of white flowers.

The Passion Flower vines on the Dunson Native Flora Garden fencing are loaded with fruits and leaves, but not many caterpillars of the Gulf Fritillary butterfly. Compare the blog post from last year at this date (September 7, 2017) with what we saw today: “. . . we found nearly all the Passion Vine leaves consumed, dozens of Gulf Fritillary caterpillars of various sizes and three or four Gulf Fritillary chrysalids.” Why there should be such a difference in abundance of the butterflies between last year and this one is an interesting question. Any suggestions?

Carla made today’s most exciting discovery: a Gulf Fritillary caterpillar that was thrashing about. A closer look revealed that a Stink bug was just above it on the vine and an even closer look showed that the Stink bug had pierced just one of the caterpillar’s last abdominal legs. Just one!

Stinkbug nymph has captured a Gulf Fritillary butterfly caterpillar and is starting to feed. Notice that the proboscis is attached to just one abdominal leg. That was all that was needed to inject venom and digestive enzymes.

Stink bugs are members of the insect order Hemiptera (pronounced: he-MIP-ter-ah) which consists of insects with piercing, sucking mouthparts: true bugs, cicadas, leaf hoppers, aphids, scale insects etc. With mouth parts like that there are only two things a bug can do: pierce and suck. What they pierce and suck makes them either predators, parasites or herbivores. The herbivores pierce and suck plants, the predators pierce and suck animals, especially other kinds of insects, and the parasites, like kissing bugs or bed bugs, pierce and suck people and/or other vertebrates.

The distinction between a predator and a parasite is sometimes fuzzy. Many Ramblers may have read Annie Dillard’s Pilgrim at Tinker’s Creek and shuddered at her description on pp. 5-6 of a frog:

“And just as I looked at him, he slowly crumpled and began to sag. The spirit began to vanish from his eyes as if snuffed. His skin emptied and drooped; his very skull seemed to collapse and settle like a kicked tent. He was shrinking before my very eyes like a deflating football. I watched the taut, glistening skin on his shoulders ruck, and rumple, and fall. Soon, part of his skin, formless as a pricked balloon, lay in floating folds like bright scum on top of the water: it was a monstrous and terrifying thing.”

A Giant Water Bug sucking the life out of a frog was the inspiration for that passage and it was just like what was happening to Carla’s caterpillar. After several minutes searching and finding only a few more caterpillars, we turned our attention back on that unfortunate caterpillar and saw it hanging, limp and motionless, still impaled on the Stink bug’s proboscis.

Predator or parasite? A predator is an organism that attacks and kills another organism and then eats it, or part of it. A parasite is usually thought of as an organism that feeds on a host organism, but does not kill the host. Bedbugs are parasites; the Giant Water Bug that Annie Dillard saw was clearly a predator. But the world often ignores the clear categories that humans create. There are insects, tiny wasps, that lay eggs on or in caterpillars. The eggs hatch into tiny grubs that begin to eat the internal organs of their host, eventually killing the host caterpillar. These creatures have some of the characteristics of parasites – they feed internally, like a tapeworm or a liver fluke, but they kill their host. Biologists call them parasitoids. If you have grown tomatoes you may have found large caterpillars (Tomato Hornworms) eating the leaves and fruits of your plants. Often, if you let the hornworms continue to devour your plants you will see them become sluggish and covered with hundreds of tiny white egg-shaped structures. These are the cocoons of a parasitoid wasp that injected eggs into the hornworm. The wasp larvae eat the internal organs of the caterpillar and then eat through the skin to pupate on the surface of the caterpillar. From each tiny cocoon a parasitoid wasp will emerge and seek out another hornworm.

Spiders:

This is the time of year when spiders are large enough to be conspicuous.

Spinybacked Orbweaver spider

We found a Spinybacked Orbweaver on its web. This strange looking spider resembles a small crab, but spins a sticky capture web just as other orbweavers do. One feature unique to its web is found in the non-sticky support strands to which the sticky capture threads are attached: the texture of the silk changes intermittently so that the silk looks like it was periodically “fluffed up.” No one knows why this is done, but it is characteristic of this kind of spider.

Clearwing Hummingbird Moth feeding on Tall Thistle.

Several Tall Thistles are currently blooming and we watched as one was visited by a Clearwing Hummingbird Moth, a day-flying Hawk moth that resembles a small hummingbird as it hovers and flies backwards and forward with all the agility seen in real hummingbirds. The food plant of the caterpillar is Viburnum.

Caterpillars: From now until late fall you will see caterpillars wandering over roads and sidewalks. These are typically the caterpillars of moths looking for a suitable place to pupate. (The caterpillars of many moth species dig into the earth and make a chamber within which they pupate.) You seldom see butterfly caterpillars doing this kind of exploration. They almost always seek out a sheltered bush or quiet place to form a chrysalis, frequently on the same food plant they have been feeding on. In the Handicapped Parking spaces in front of the Visitor Center we found a yellow striped caterpillar crossing the road.

Yellow-necked caterpillar

It was a Yellow-necked caterpillar (Datana ministra), a species that feeds on a variety of trees and shrubs.

Horse Nettle flowers

The flowers of the Horse Nettle should remind you of Tomato blossoms. The similarity is due to their relationship to Tomatoes, Potatoes, Eggplant and other plants in the Nightshade family (Solanacea). These all have a similar flower with an unusual anther. The typical plant anther splits down its length to release the pollen within. The anthers of solanaceous plants has a tiny opening at the very end: it is called a poricidal anther. The pollen within is dry and not sticky as pollen of insect pollinated plants often is. Only a few bees, bumblebees, can successfully pollinate such plants. They do so by grasping the anthers and rapidly contracting their wing muscles. This makes a buzzing sound and vibrates the anthers, shaking the pollen out. The dusty pollen is attracted to the hairy body of the bumblebee by a difference in electrical charge. As bees fly through the air they create a static charge much like running a comb through your hair does. Honeybees cannot “do the buzz” and are very inefficient pollinators of such plants.

DYC is short for “Darn Yellow Composite” and Late summer--early fall is their flowering season. Sunflowers and their many look-alikes are in the Composite Family (Asteraceae). Today we saw Rough-leaved Sunflower in the lower powerline right-of-way; in the upper right-of-way, Starry Rosin-weed and Woodland Tickseed are still in flower. How to tell these yellow-flowered composites apart? One place to start is learning to recognize the different genera in this family by their involucral bracts—the whorls of small green bracts that encircle the base of the flower heads of all species in this family. Here are some photos that illustrate the different types of involucres of some common composite family genera:

Sunflower involucral bractsCredit:  Dan Tenaglia, Missouriplants.com

Rough-leaved Sunflower:  The genus Helianthus usually has several whorls of bracts that all look alike; each bract is lance-shaped with tapered, spreading tips. 

Silphium incolucral bractsCredit:  Janie Marlow, NameThatPlant.net

Starry Rosin-weed:  The genus Silphium has fewer, broader bracts, each one broadly triangle-shaped and often curved outwards at the tip.

Coreopsis involucral bractsCredit:  Janie Marlow, NameThatPlant.net

Woodland Tickseed: The genus Coreopsis has the most distinctive involucre of any composites in this area. The bracts are in two very different series: the outer series’ bracts are narrow, green, and spreading; the inner series’ bracts are broader, yellowish, and tightly pressed against the base of the flower head.

The edges of the leaves of C. terniflora (Sweet Autumn Clematis) are smooth (L) while those of the native C. virginiana (Virgin's Bower) are serrated (R).Credit: University of Wisconsin-Extension Master Gardener Program

Virgin's Bower flowers are peaking now. Our native species of Virgin’s Bower have leaves consisting of three toothed leaflets. We noticed that some of the leaves close to the tips of the vines had leaflets with smooth margins, potentially confused with the exotic invasive species, Sweet Autumn Clematis, whose leaflets have smooth, toothless margins.  

Arrow-leaf Tearthumb; the spiny stems give it its name.

Arrow-leaf Tearthumb is one of the smartweeds, in the same genus Persicaria as Dotted Smartweed and Pennsylvania Smartweed. They all have the characteristic “ocrea” that is unique to this plant family, the Polygonaceae. An ocrea is a sheath or sleeve that arises from the base of the leaf stalk and wraps around the plant’s stem.

Common Dodder, a parasitic plant; note the flower buds and the haustoria swelling where the orange stem is in contact with the host plant.

Common Dodder is one of eight species in the genus Cuscuta that occurs in Georgia. All dodders are parasitic plants, deriving moisture and all their nutrients from their host. The stems are orange (no chlorophyll) and there are no leaves (who needs ‘em when you are stealing all your food?). Dodder seedlings have roots but as soon as the growing plants make contact with a host plant, the roots wither away. Dodder sinks tiny peg-like structures, called haustoria, into the vascular system of the host and begins to shunt resources into its own vascular system. The host plant tries to defend itself against this thievery by producing a protein that blocks the flow of nutrients to dodder. But dodder is one step ahead: when it connects to the host, it inserts genetic material that blocks the formation of the clotting protein. The nutrients and water are then able to flow freely into the dodder plant. Various species of dodder are a major agricultural pest on other continents, so plant scientists are exploring how to prevent dodder from hijacking the clotting protein. Fortunately, none of the Georgia species are a problem for farmers and none are known to be a threat to other native plants.

Virginia Dayflower

Virginia Dayflower, a native dayflower species, has three blue petals; the exotic Common Dayflower has two blue petals and a tiny, white, third petal.

 
SUMMARY OF OBSERVED SPECIES:

Painted Lady (caterpillar)	Vanessa cardui
Angelonia	Angelonia angustifolia
Fragrant Lady's Tresses orchid	Spiranthes odorata
Purple Passionflower	Passiflora incarnata
Gulf Fritillary (caterpillar)	Agraulis vanillae
Spined Soldier Bug	Podisus maculiventris
Green Crab Spider	Misumessus oblongus
Yellow Crownbeard	Verbesina occidentalis
Wingstem	Verbesina alternifolia
Frostweed	Verbesina virginica
Spinybacked Orbweaver	Gasteracantha cancriformis
Rough-leaf Sunflower	Helianthus strumosus
Virgin's Bower clematis	Clematis virginiana
Tall Goldenrod	Solidago altissima
White Crownbeard	Verbesina virginica
Maryland Senna	Senna marilandica
Tick Trefoil	Desmodium sp.
Camphorweed	Heterotheca subaxillaris
Tall Thistle	Cirsium altissimum
Clearwing Hummingbird Moth	Hemaris thysbe
Eastern Tiger Swallowtail (dark form female)	Papilio glaucus
Tall Ironweed	Vernonia altissima
White Morning Glory	Ipomoea lacunosa
Arrowleaf Tearthumb	Polygonum punctatum syn. Polygonum sagittatum
Dotted Smartweed	Persicaria punctatum syn. Polygonum punctatum
Pennsylvania Smartweed	Polygonum pensylvanicum syn. Persicaria pensylvanicum
Red-root Flatsedge	Cyperus erthrothizos
Carolina Horsenettle	Solanum carolinense
Dodder	Cuscuta sp.
Stout Wood Reed	Cinna arundinacea
Mikania/Climbing Hempweed	Mikania scandens
Virginia Dayflower	Commelina virginica
Yellow-necked Caterpillar	Datana ministra