Today's Ramble was led by Dale Hoyt.
All the photographs of today’s ramble, except where otherwise
credited, were taken by Ted LaMontagne; they can be seen on the SBG Nature
Rambling Facebook album.
Today's post was written by Dale Hoyt.
11 Ramblers met today.
Today's reading:
None today.
Show & Tell:
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| Pink-Striped Oakworm Moth |
Richard brought a female Pink-Striped Oakworm moth, Anisota
virginiensis. This beautiful moth had already laid a few yellow eggs in its
container. Richard, you can feed the caterpillars Oak leaves and raise a new
generation.
In many moths the males and females have distinctly different
antennae. The male antennae are feathery whereas the females are threadlike.
This difference reflects the use of the antennae as organs of smell. Virgin
female moths typically emit a chemical substance called a pheromone, which is a
sexual attractant. The males, with their well-developed antennae are able to
detect the faintest concentrations of the pheromone in the air. They then fly
toward the highest concentration until they locate the female and mate with
her.
As their name implies, the Oakworm caterpillars eat Oak leaves.
The Oakworm moths are in the silkmoth family, Saturniidae,
and the moths of this family have vestigial mouthparts. The males die soon
after mating and the females die after laying their eggs, never having eaten as
an adult.
I brought in some branches I clipped from a Scarlet Oak, Quercus coccinea, and a White
Oak, Q. alba to demonstrate how
trees grow and how long it takes some oaks to produce acorns.
Growth in trees
is from the buds at the ends of twigs, called terminal buds. These buds contain
embryonic shoots. (The other buds are found where leaf stalks join the twigs or
branches; they contain embryonic shoots, flowers or leaves. They are called
lateral or axillary buds) In most trees the terminal buds are protected by a cluster
of overlapping scales. In the spring the bud scales fall off as the shoot inside
starts to elongate. They leave a scar where they were attached to the twig and
this mark persists for several years, enabling us to see how much a twig has
grown by looking for the bud scars. Each scar surrounds the twig and the
distance between bud scars is the amount that the twig grew during one year. The
current years spring growth is usually a light shade of green in the early
weeks, gradually darkening to brown as spring progresses. This makes it easy to
see which branches are growing the most. In the trees around my house the
longest new growths are seen in branches that get the most sunlight. The new
growth on one branch of a White Oak I measured was already 19 inches. Other
branches on the same tree were in shaded locations and had less growth.
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| Scarlet Oak leaf Note bristle tips of the lobes, characteristic of the red oak group. The deep sinuses are characteristic of Scarlet Oak. |
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| White Oak leaf Note the rounded lobes and absence of bristle tips, characteristic of the white oak group. |
Oak species are subdivided into several different groups.
In our area there are just two of these groupings: Red oaks and White oaks. Scarlet
Oak is in the Red oak group of species. This oak group usually has lobed
leaves, each lobe being pointed and ending in a bristle tip. (The lobes of the White oak group
are rounded and lack the bristle.) Scarlet Oak leaves can be told from other
Red oak group species by their deep sinuses (the space between adjacent lobes).
They reach almost to the midvein in Scarlet Oak. In Northern Red Oaks the
sinuses are much shallower.
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| Developing Scarlet Oak acorns (photo by Dale Hoyt) |
The acorns of trees in the Red oak group take two years
to mature, so you will find them developing on last years growth, which is just
inside the green shoots of this year’s new spring growth. In contrast, White
oak acorns develop in less than one year, maturing and falling to the ground in
the same year as they begin development.
As we walked down the access road we noticed several
plants in the Dunson Native Flora Garden growing next to the deer fence. Silky Dogwood, Cornus amomum, is producing clusters of tiny buds that have not
opened yet. A single example of Southern
Sundrops, Oenothera fruticosa, a
yellow flowered plant in the Evening Primrose family, also growing by the fence.
The Purple Passionflower, Passiflora incarnata, vines that cover
the deer fence later in the year are about a foot high. These are the food plant
for the caterpillars of the Gulf Fritillary butterfly. Come late summer they
will be stripped of their leaves by all the caterpillars.
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| A group of Curly-Leaf Yucca at the bottom of the Dunson Native Flora Garden |
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| A yucca flower, petals peeled back to expose the pistil, in the center, surrounded by the stamens. |
The Curly-leaf Yucca,
Yucca filamentosa, at the bottom of
the Dunson Garden is producing large inflorescences, but no buds are open yet.
I brought some yucca flowers for ramblers to look at. The stigma, the part that
receives pollen, is recessed in the tip of the pistil. It is here that the
yucca moth tamps in a ball of pollen to fertilize the ovules in the ovary. The
moth then lays eggs in the ovary wall. The eggs will hatch into caterpillars
that will begin to eat the developing seeds in the yucca ovary, seeds that
would not appear if the mother moth had not pollinated the plant. If there are
a small number of caterpillars in the ovary not all of the developing seeds
will be eaten. When too many caterpillars are present, as when several moths lay
their eggs in the same ovary, the plant will abort the fruit. How the yucca
knows how many caterpillars there are in a developing fruit is one of those
mysteries of biology.
The High Bush
Blueberries, Vaccinium corymbosum,
just outside the deer fence at the bottom of the Dunson Garden are laden with
lots fruit. Where the power line right-of-way crosses the road there is a
grassy area at the base of the hill that is protected from mowing. It has numerous
plants of Butterfly milkweed, Asclepias tuberosa, currently about a
foot tall at the bottom of the hill to the north of the road. Unopened flower
buds are present in most of the plants. This species of Milkweed is used as a
food source for the caterpillars of Monarch butterflies.
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| Hairy Cat's Ear (photo by Don Hunter) |
An occasional Hairy
Cat’s Ear, Hypochaeris radicata,
is blooming now here and in lawns all over Athens. It’s often mistaken for
Dandelion, but Cat’s Ear has solid, green flower stems that bear more than a
single flower. Dandelion flowers are born on hollow, tan flower stems that
always have a single flower.
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| Spittle bug "nest" |
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| Spittle removed to show the guilty party -- a spittle bug nymph. The dark structures are developing wings, they get a little larger each time the spittle bug sheds its skin. At the last molt they are fully developed and the adult jumps and flies away. |
We found a drop of spittle on one of the Hairy Cat’s Ear.
This is the protective home for the immature stage of a spittlebug. It’s not a
true bug – it’s a leaf hopper, a group of insects that are related to aphids, cicadas
and other similar sap sucking insects. Inside the spittle you will find the
small, wingless nymph of the adult leaf hopper. The frothy, sticky spittle
protects it from attack by predators and parasites. The spittle is a mixture of
spittlebug poo that has been kicked into a frothy bubble, surrounding the
nymph.
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| Unoccupied Martin house with Bat house on the pole beneath. |
Further up the hillside there is a Martin house, not yet
occupied. It is located in a test plot, started 3-4 years ago. In the past this
part of the Garden was originally a lawn of Bermuda grass.
The Garden recently started
a project to convert this hillside into a Piedmont Prairie, an endangered type
of habitat that was formerly more common in Georgia. In order to do this the
Bermuda grass must killed and replaced with native herbs and grasses. Since
Bermuda is notoriously difficult to eradicate several test plots were created
to test different removal methods. The grass was successfully eliminated on one
plot which was then planted with a variety of plants typical of the Piedmont Prairie.
Keep your eye on this plot and see what herbs bloom here. Already one of the Beebalms, Monarda sp., has flowers.
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| Piedmont Prairie test plot |
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| An old Cedar Apple Rust fungus |
At the White Trail we turned right and searched the
Eastern Red Cedar to see if the recent rains had allowed the Cedar Apple Rust to disperse its
spores. We only found the remains of last year’s galls.
In addition to the rust
galls we were pleased to find two Praying
Mantis egg cases, one of which looked like it had been nibbled on. Each egg
case was deposited last fall by a female Mantis. As the eggs are laid they are
covered with additional secretions that waterproof and insulate them. There may
be 50-100 eggs in each case and they will hatch in late spring, early summer.
The young disperse after hatching, preying on smaller insects. They ultimately
reach a size of four to six inches in length, depending on species. The larger individuals
are capable of killing hummingbirds, but that happens only very rarely.
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| Praying Mantis egg case, part on right has been nibbled away. |
What is a gall?
A gall is an abnormal growth on a plant. A variety of things can cause galls:
insects, mites, fungi of various types. Some galls are misshapen, amorphous,
irregular. Others are species specific and have a consistent appearance. An
example is the gall caused by an aphid and commonly found on Witch Hazel leaves.
We have seen this gall on many previous rambles.
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| Winged Elm branch with leaves; note the corky ridges on the branch. |
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| Hophornbeam leaves. The red object on the leaf below the thumb is a gall. |
Nearby we had an opportunity to compare Winged Elm, Ulmus alata, with Hophornbeam,
Ostrya virginiana. Many ramblers have
trouble telling the difference between these trees. Maybe this will help: First
look at the leaves. Winged Elm leaves are almond shaped, widest at the middle and
symmetrical about the middle. (Some people think they are eye-shaped.) In contrast,
Hophornbeam leaves are broadest closer to the base and they taper to a point at
the far end, while the end near the leaf stalk is more rounded. Now look at the
edge of the leaf. Both trees have jagged edges, like the teeth of a saw blade, a
condition called “serrate.” But the serrations are larger in Winged Elm and the
Hophornbeam leaf is doubly serrate, i.e., the serrations also are serrate.
Finally look at the base of the leaf blade where it meets the leaf stalk. It is
asymmetrical in Winged Elm and symmetrical in Hophornbeam. Another difference
is unrelated to the leaves. The branches and twigs of Winged Elm sometimes have
ridges of corky tissue. Unfortunately, the number of wings varies considerably among
plants, so it is not very reliable. When present it is proof, but when absent
you need to look carefully at other characteristics.
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| Possibly an ant foraging trail. These appear after rains. |
No ramble would be complete without a mystery. After rains we often find the trails of fresh earth piled up in a line across the path. I suspect this is the top of a tunnel made by ants to allow them to travel to foraging areas without being exposed to predators. At least that is my hypothesis. You are welcome to speculate, too. Biology is full of the unexplained.
And, with our heads spinning over the subtle distinctions
between Hophornbeam and Winged Elm, we ran the gauntlet of mosquitoes back to
the Visitor Center.
