Today's Ramble was led by Dale Hoyt.
Here's the link
to Don's Facebook album for today's Ramble. (All the photos in this post are
compliments of Don, unless otherwise credited.)
Today's post was written by Dale Hoyt.
Today’s Focus:
Seeking what we find in the formal gardens.
25 Ramblers met today.
Announcements:
1.
On November 6, 2019, the First Wednesday
Guided Walk at SCNC, will be lead by Dan Williams. Many Ramblers know Dan
from the tree ID walks he led in the Oconee Forest before retiring from UGA. He
also taught a course in Georgia geology for the Botanical Garden.
2.
The Native Plant Sale is ongoing, Thursday, Friday, Saturday next weekend.
Today's reading: Dale read the September 25 entry
from
Donald Culross Peattie’s An Almanac for Moderns:
Now is that opulent moment in the year, the
harvest, a time of cream in old crocks in cool, newt-haunted spring- houses, of
pears at the hour of perfection on old trees bent like women that, as the Bible
says, bow down with child. In this field the grain stands, a harsh forest of
golden straw nodding under the weight of the bearded spikes, and in that, it
has been swept and all its fruitfulness carried off to fill the barns.
One will not see here, save in the steep
tilted Blue Ridge farms, the man reaping by sickle in his solitary field, while
his daughters bind the sheaves, nor the bouquet of wheat and pine boughs hung
above the grange gable that is crammed to the doors. But we have our own sights
and sounds at harvest time. There is the roar and the amber dust of the
threshing machines, the laughter of the children riding home on the hayricks,
the warfare of the crows and grackles in the painted woods, and the seething of
juice in the apple presses. Then night falls and the workers sleep. The fields
are stripped, and only the crickets chant in the midnight chill of the naked
meadow.
Today's
Route: We went
through the Visitor Center to the Herb Garden, then through the Heritage Garden
to the Flower Garden where we stopped at one of the lantana beds then returned
back to the Visitor Center, through the Heritage Garden and assorted flower
beds. Many of us then retired to the Café Botanica for refreshments and
conversation.
===== Note: to enlarge a photo, click on it
===== A second click returns you to the blog post.
Plaza Fountain:
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| Long-jawed Orbweaver spider |
A Long-Jawed Orbweaver Spider was suspended on a single
web strung between two pitcher plants. These spiders are commonly found in
grasses or sedges near water. They hide by aligning themselves on a stem with
their legs stretched out, fore and aft, making them almost undetectable.
Herb Garden:
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| Cloudless Sulfurs visiting Pineapple Sage flowers. |
As we saw last week, Cloudless Sulfur butterflies were
swarming about all the Pineapple Sage. (Previously we misidentified this
red-flowered plant as either Scarlet Salvia or Red Sage or Scarlet Sage.)
Reviewing why these butterflies are called “cloudless”:
Look at the two photos that follow. The first shows a Cloudless Sulfur, upper
surface of the wings on the left, lower surface of the wings on the right.
Notice that neither the upper or lower surface has an extensive black area.
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Photo of Cloudless Sulfur upper (L) & lower (R) wing surface
Credit:Geoff Gallice [Wikipedia CC BY 2.0]
|
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| A Clouded Sulfur, back lighted to show the dark border of the wings. Credit: Wikipedia: Paul Stein from New Jersey, USA [CC BY-SA 2.0] |
The Clouded Sulfur is uncommon in the south (it is more common
in the Midwest). It breeds on clover.
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| We noticed an ant, a fly and a yellow jacket consuming a dead grasshopper on the paver path |
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| Eastern Black Swallowtail caterpillars feeding on Parsley. Near the center is a younger, smaller, darker caterpillar with the "bird dropping" pattern. Which one would you eat? |
Eastern Black Swallowtail caterpillars have
decimated the parsley plants. Their appetites are ravenous and, as they
increase in size with each molt, the amount they eat increases exponentially. Most
of the older, larger caterpillars are green with a black band across the middle
of each body segment. The black band has six yellow or orange spots. The
coloration of the earlier, smaller, caterpillars is brown or black with a white
“saddle”. This pattern resembles a bird dropping.
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| Monarch caterpillars Notice there are no green bands, the black bands lack yellow or orange spots and the caterpillars have black filament both fore and aft. |
Sometimes people mistake the Black Swallowtail
caterpillar for a Monarch caterpillar, but the two are very different. The Monarch
caterpillar has black, white and yellow bands and a pair of black filaments on
segments near the front and on the back. They feed on milkweeds. Black
Swallowtail caterpillars feed on plants in the carrot family: parsley, fennel,
dill and carrots.
Heritage
garden
A spider web was attached to one of the posts by the
walkway, but no spider was visible. Some spiders don’t sit on their webs during
the day, only at night. They usually build a retreat nearby – a cluster of leaves
or even a single leaf that is curled up to form a hide-away in which the spider
rests. One of the support lines of the web will lead to this shelter. All you
have to do is carefully examine the silk lines outside of the sticky center of
the web. Eventually, you’ll find one that leads to a shelter made of one or
more leaves.
We were successful in finding this spider’s retreat in a curled
Ginkgo leaf.
Hidden inside the leaf was a large, yellow, round and orange-legged
spider: A Marbled Orbweaver.
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| A curled Ginkgo leaf. Guess what's inside! |
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| Marbled Orbweaver spider inside its Ginkgo leaf retreat. |
Ramblers had many questions about the web construction.
Answers to some of them follow.
How the web is built
The following illustration shows, in diagrammatic form,
the step by step process of web construction. It begins with a horizontal line
of silk, the bridge line or thread, at the top of the diagram.
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| Diagram showing the steps in construction of an orb web Credit: Wikipedia: Dav92ide (CC BY-SA 4.0] |
Forming the bridge thread
The spider selects a spot and sits with its abdomen
elevated. It secretes a thread of silk from its spinnerets. This thread has a
sticky end. The silk is very fine and light and is easily swept away by the
slightest of breezes. When the sticky end hits a structure it adheres to it and
the spider senses when that happens. A tug on the silk line reveals if it is
attached or not. If it’s attached she anchors her end of the line and scrambles
across the bridge to the other end, producing another silk line as she goes.
This bridge line will ultimately consist of two or more strands of silk bundled
into a single line.
Next another thread is attached to both ends of the
bridge line but kept separate from it. The spider walks to the approximate
center of this loose line, attaches the end of a silk line at that point and
then drops to the ground. The loose line stretches from the weight of the
spider and she, simultaneously, secretes more silk to lengthen the line from
the middle of the loose line. When she reaches the ground or another object she
glues the silk like to it. This creates a Y-shaped framework for the beginning
of her orb web.
The diagram shows the completion of an idealized web and
you should be able to follow it to completion, if you’re still interested.
Also, if you’re interested, Wikipedia has a very
in-depth summary of the properties of different spider silks.
The Marbled Orbweaver web appears empty while the spider
hides in its retreat during the day. At night it occupies the center of the
web. Other species occupy the web continuously and have no shelter. When a web
becomes damaged it is repaired or rebuilt. The existing web is eaten first and
then remade. Silk is made of protein and eating the web allows the protein to
be recycled into the new web construction.
Capturing prey
When the spider is hiding in its retreat it has a silk
signal line attached to one of its feet. The other end of the line is attached
to the orb. When an insect hits the orb the spider feels the disturbance via its
signal line and rushes out of its retreat to the point where the struggling
prey is located. If the prey item is small it is wrapped in silk immediately.
Larger prey are bitten first, injecting a venom that paralyzes them. This
allows the spider to more easily wrap them up. All this action takes but a few
seconds.
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| Spider wrapping prey in thick bands of silk. |
The prey is simultaneously revolved by the spider’s feet
as it ensheaths its victim with silk
from its spinnerets. In just a few more seconds the entire prey is completely
covered by silk and the spider either hangs it on the web or carries it to its
retreat and hangs it there.
It’s like a sack lunch on your desk – you can get a
snack anytime you’re hungry.
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| Spider carrying wrapped prey back to its retreat. |
How spiders eat
Spiders “spit” a mixture of digestive enzymes on their
captured prey and then begin to chewing at that point, which mixes that part of
the victim with the digestive juices. The liquid slurry is then swallowed and
further digested. The process is repeated until only the indigestible parts,
mostly fragments of the victim’s exoskeleton, remain. They are merely dropped
to the ground.
The mouthparts that do the chewing of the prey also bear
the fangs through which the spider’s venom is injected. The base of these structures
do the mincing and chopping of the prey.
Most of the spiders you see on large webs are female. In
spiders the males are smaller than the females, sometimes much smaller. They build
small, inconspicuous webs lower in the vegetation. If they are interested in
mating they often lurk about the web of a female, waiting for an opportunity to
court her. They need to be cautious because she will often treat them as prey
and eat them.
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| Spinyback Orbweaver Notice the "fuzzy" parts of the silk strands. Their function, if any, is unknown. |
Another common spider we often see this time of year is
the Spinyback Orbweaver that looks like a colorful crab in the middle of
the web. The web anchor lines of this species have alternating smooth and fuzzy
segments. I’ve been unable to find out how the fuzzy parts are formed. It’s been
suggested that the fuzzy part makes the web more conspicuous to birds, allowing
them to avoid flying into it. Or, it could attract insect prey toward the web.
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| A Mantis (Chinese or European) |
We noticed a large Mantis clinging motionless on the
flowers of a Cleome. These insects are frequently called “praying” mantises
because when the forelegs are folded up and held against the body the mantis
resembles a supplicant in prayer. A better descriptive name would be “preying”
mantis, because these insects are sit-and-wait predators. The forelegs are
modified for the capture of prey. They are so effective in holding their prey that
they are called “raptorial,” a reference to the clawed feet of hawks or owls.
The last two parts of the leg, the tibia and tarsus, are covered with sharp
pointed projections that securely hold whatever is grasped between them. The
strike is also very rapid, taking only a fraction of a second. Check out this video of
mantids to see how fast their strike is.
I forgot that there are two possible species of large,
green, non-native mantis here: the European Mantis and the Chinese Mantis. The
European Mantis has a black-ringed white spot on the inside of the foreleg; the
Chinese Mantis lacks that spot. On Thursday I forgot about the difference and
didn’t look, so I don’t know which of the two we observed. Mea culpa.
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| A Mantid egg case. The coating is waterproof and protects the developing eggs during the winter. |
Mantids grow rapidly in just a few months to reach the
size of the female mantid we saw. Thursday. Her abdomen was distended with eggs
that she will lay soon. Instead of dribbling them out, one by one, she will
deposit them in a single mass of about 50 to 100 eggs. As she lays them, she
produces a frothy substance that surrounds each egg and hardens into a
waterproof covering. The mass of eggs is a little smaller than a golf ball and
is cemented around a weed stalk. It will survive through the winter and all the
baby mantids will hatch at about the same time next spring.
Flowering plants have little control over who they mate
with. They depend on the wind or animals to carry pollen to fertilize their
seeds. But this runs the risk of being fertilized by their own pollen,
resulting in self-fertilization. Flowers that self-fertilize produce fewer
seeds and seeds that produce weaker plants. The solution to this problem is to
promote out-crossing, mating with unrelated individuals.
One way to promote out crossing is to separate the sexes.
Instead of having flowers with both pollen and seed producing structures
(stamens and pistils), make unisexual flowers. This is the solution adopted by
the cucurbits (gourds, melons, squash, pumpkins, family Cucurbitaceae) and
other plants like corn. In corn all the pollen producing flowers are gathered
together in the “tassels” at the top of the plant. All the seed producing
flowers are gathered together in the “ears.” In the cucurbits, like the Loofah
gourds we saw, the male flowers tend to be found at the ends of the shoots and
the female flowers further toward the shoot base.
This condition, where the unisexual flowers of both sexes
are on the same plant, is called monoecious. Approximately 5% of
flowering plants are monoecious.
Being monoecious doesn’t eliminate the possibility of self-fertilization,
it just reduces it. Since each plant bears both sexes of flower pollen transfer
can occur between the male and female flowers of the same plant. This problem
is eliminated in plants that are unisexual – all the flower on a single plant
are either male or female, but never a mixture. This condition is called dioecious.
Roughly 5% of flowering plant species are dioecious. Examples include Hollies,
Persimmons and Wax Myrtles. If you want the fruits of these plants you will
need to make sure that you plant both sexes near each other.
Why these mating systems are in such a minority is still
not known, but may involve a third method of avoiding self-fertilization:
self-incompatibility. When a plant is self-incompatible pollen from the same
plant is unable to fertilize the ovules of flowers on that plant. How that
works is a story for another time.
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| A female Loofah gourd flower; the stalk between the petals and my fingers is the enlarged ovary. Such as swollen structure is not found in male flowers. |
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| A developing Loofah gourd; when ripe it can be dried and the skin removed and the fibers cleared of seeds to make an exfoliating sponge. |
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| A male Loofah flower. |
[male and female loofah flowers
The Loofah gourd is a monoicous plant with flowers
of two types: pollen producers or seed producers. Being able to identify which
is which is easy if you look for the ovary. It is a swollen part of the stem
just below the petals. No swelling, it’s a male; swelling, a female.
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| The wicked thorns and ripening fruit of Trifoliate Orange. |
Trifoliate Orange has intimidating large thorns seemingly
everywhere. Native to China, they have been planted in many other parts of the
world as hedges. The fruit is so bitter that it is considered inedible, but has
been made into marmalade. This plant is more cold-hardy than most other citrus
varieties and, for that reason, has often been used as the root stock for
grafting less hardy citrus varieties. The downside is that when abandoned citrus
orchards have been cut down, the root stock survives and regrows the Trifoliate
Orange tree. It was also used as an impenetrable hedge. But in some areas it has
rapidly expanded it distribution. The fact that is not eaten by deer also gives
in an advantage. It is currently considered an invasive species.
Root grafting is used for a variety of purposes in
addition to improving cold hardiness. Nurseries use it to more rapidly propagate
their stock and to increase the rate of growth newly developed plant varieties.
One of the most famous cases involving root grafting
happened to the French wine industry in the mid-19th century. An
aphid began to destroy the grape plants in the French wine vineyards. An
American entomologist, Charles V. Riley, identified the aphid as American in
origin and suggested that the French graft their varietal grapes to the roots
of American grapes that were resistant to the aphid. His suggestion saved the
French wine industry and he was awarded a medal and named a Chevalier of the
Legion of Honor.
Bald Cypress is a coniferous plant related to
pines, but, unlike the pines, it drops all its leaves in the winter and
replaces all of them in the spring.
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| Long tassels of Bald Cypress male cones. |
The male cones develop on long tassels, separately from
the female cones.
Female cones are spherical and look like small golf balls.
They are made of about a dozen, swollen scales. Pollination is by the wind.
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| Linda cut off a piece of this Bald Cypress female cone. It clearly shows the large, crowed cone scales. The brown objects are developing seeds. |
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Bald Cypress ripe cone
Credit: Sheryl Pollock
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When
the female cones mature they change color from green to brown and fall apart,
releasing the seeds.
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Bald Cypress seeds
Credit: Steve Hurst, USDA-NRCS PLANTS Database
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SUMMARY OF OBSERVED SPECIES:
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Long-jawed Orbweaver
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Family Tetragnathidae
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Cloudless Sulphur
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Phoebis sennae
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Pineapple Sage
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Salvia elegans
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Grasshoppers
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Order Orthoptera: Acrididae
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Eastern Yellow Jacket
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Vespula maculifrons
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Ants
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Family Formicidae
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Fly
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Order Diptera
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Eastern Black Swallowtail
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Papilio polyxenes asterius
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Marbled Orbweaver
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Araneus marmoreus
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Mantis
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Tenodera sinensis or
Mantis religiosa
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Cleome/Spider Flower
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Cleome sp.
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Gulf Fritillary
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Agraulis vanillae
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Lantana
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Lantana camara
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Spiny-backed Orbweaver
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Gasteracantha cancriformis
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Loofah (or Luffa)
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Luffa aegypitiaca
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Carpenter Bee
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Xylocopa virginica
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Bumblebee
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Bombus sp.
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Syrphid Fly
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Family Syrphidae
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Trifoliate Orange
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Poncirus trifoliata (= Citrus
trifoliata)
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Bald Cypress
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Taxodium distichum
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