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.)
Today's post was written
by Dale Hoyt.
Today’s Focus: Passion
vines on the deer fence and the fall flowers still blooming in the power line
right-of-way.
21 Ramblers met today.
Announcements:
1. Linda announced an organizational meeting for those
Ramblers interested in forming a book club devoted to reading “nature” books,
both fiction and non-fiction. This meeting will take place next Thursday after
the Ramble in the adult education room at the Garden. Those interested should
come with ideas for how often we should meet, when and for how long, what their
expectations are and what kinds of books to read.
3. Dale reminded us of the upcoming talk by Andrea
Wulf, noted historian and award winning author will be speaking at the Chapel
on the UGA campus at 4 pm on October 18th. Some Ramblers may
remember her appearance here a few years ago. If you missed that presentation
this will be your chance to see what a brilliant speaker she is! For
more information visit this website.
4. Next Wednesday, Oct. 3, there will be a guided tree
walk at Sandy Creek Nature Center. The walk meets at 9:00 am and refreshments
will be served afterwards.
Today's readings: Kathy
read “One Who Teaches” by the English theologian Isaac Watts (1674-1748):
“He should have so much of a
natural candour and sweetness mixed with all the improvements of learning, as
might convey knowledge into the minds of his disciples with a sort of gentle
insinuation and sovereign delight, and may temp them into the highest
improvements of their reason by a resistless and insensible force.”
Dale read Donald Culross
Peattie’s tribute to the Harvest Moon:
I
TRY each year to disbelieve what my senses tell me, arid
to look at the harvest moon in a cold and
astronomical light.
I know that it is a small cold sphere of rock,
airless, jagged
and without activity.
But the harvest moon is not an
astronomical fact. It is a knowing thing, lifting
its ruddy face
above the rim of the world. Even to the
thoroughly civilized mind, where caution for
the future is supposed to rule all impulse,
the orange moon of autumn invites the senses
to some saturnalia,
yet no festival of merriment. The harvest moon has no innocence, like the slim quarter moon of a spring twilight,
nor has it the silver penny brilliance of the moon that looks down upon the
resorts of summertime. Wise, ripe, and portly, like
an old Bacchus, it waxes night after night.
Show & Tell: Richard
brought a large Black Walnut fruit and cut it open, revealing dozens of fly
maggots consuming the husk.
The actual nut, inside the husk appeared to be
untouched.
 |
| Walnut Husk fly maggots feeding on the husk of a Black Walnut |
Today's route: From the
Entrance Plaza we walked down the road to the deer fence and the power line. We
returned through the woods via the White Trail spur to the Café Botanica for
conversation and beverages.
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| Two Salvia flower with the base cut open by Bumblebees to access nectar at the bottom of the blossom. |
Nectar Robbing: At the
Entrance Plaza there are pots planted with red and white Salvia and most of the
blossoms have been robbed of nectar. Bumblebees are the principal thieves.
Salvia has a tubular corolla with the nectar glands located at the base. The
male and female structures are located at the other end and arranged so that a
pollinator entering the flower will pick up and deposit pollen. Bumblebees find
it simpler to bite a hole at the base of the flower and sip the nectar
directly, by passing the “legitimate” entrance.
Rough Green Snake: Our
first surprise was a Rough Green Snake (RGS), dead in the road, run over by a
car. The RGS is very innocuous and never bites, even when roughly handled. Their
solid green coloration makes them perfectly camouflaged when climbing in
vegetation. Contributing to their concealment is their habit of ceasing
movement when disturbed, which makes them even harder to see. That behavior was
probably what doomed this snake. It was crossing the road and the approaching
car must have caused it to freeze. Sometimes behavior patterns that are
adaptive in one context are not in a different one.
Many Ramblers wanted to
know why it is called the Rough Green
Snake.
It’s because each scale on its body has a narrow ridge, called a keel, that
runs down the center of each scale, parallel to the body axis. This makes the
texture of the skin rougher in comparison to snakes with smooth scales. Some
Ramblers didn’t think it felt rough to their touch, but they never compared it
to the Smooth Green Snake, which is not found in this area. The keel can easily
be seen with a hand lens or felt by sensitive fingers.
 |
| The keeled scales of a Rough Green Snake. |
Caterpillars: The deer
fence is an easy place to find caterpillars that have finished eating and are
wandering about, looking for a place to pupate. (Pupate means to form a pupa,
the stage of insect development between the larva and the adult. In butterflies
the pupal stage is called a chrysalis; in moths, the pupa is usually formed
inside a silk cocoon.)
Today we found caterpillars of the Fall Webworm moth and
a White-marked Tussock Moth on the deer fence, plus a Yellow-striped Army Worm on
Dog Fennel in the power line ROW.
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| Fall Webworm caterpillar |
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| White-marked Tussock moth caterpillar; note the four tussocks of white bristles |
Tussock moth caterpillars
get their name from the tufts of white bristles that are gathered into dense clumps
at several places on the caterpillar. (The dictionary definition of a tussock
is an area of tall grass surrounded by shorter grasses.) It has been suggested
that the tussocks on the body of the caterpillar resemble the cocoons of
parasitoid wasps and serve to ward off further attacks by the wasps. This idea
has never, to my knowledge, been tested, but it is an interesting speculation. Here’s
a photo of the cocoons on a tussock moth caterpillar from last week’s Ramble.
Apparently the wasps are unable to read our books.
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| The parasitiod wasp that laid eggs in this Tussock Moth wasn't fooled. The things that look like rice grains are the cocoons of the larvae that ate the internal organs of the caterpillar. |
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| Yellow-lined Army Worm caterpillar |
The Army Worm is another
moth caterpillar; its name refers to the habit of some species of crawling in
large aggregation to new food plants.
 | |
| Yellow Bear caterpillar of the Virginian Tiger Moth |
A Yellow Bear
caterpillar was found on Wingstem in the power line RoW. The common name is
unfortunate because the caterpillar is quite variable in color. This individual
was a dark reddish brown.
Some caterpillars with
dense bristles will cause itching or actual stings, like nettles, if they are
handled. Many are harmless, though. To be safe, you should avoid touching them
unless you know what kind they are.
Passionflower vines: The
passionflower vines we periodically visit are still showing very few signs of
attack by Gulf Fritillary caterpillars and we only found two caterpillars and one
chrysalis.
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| Gulf Fritillary caterpillar |
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| Gulf Fritillary chrysalis |
The Gulf Fritillary is not
a resident species in our area. None of its life stages (egg, caterpillar,
chrysalis, butterfly) can survive our winters, mild as they are. The
butterflies must recolonize this area each year from populations living in
peninsular Florida. This takes time and depends on weather conditions. Timing
with the growth of the host plant, Purple Passionflower, is also important. In
our area passion vines start growth in late spring, early summer. If the
butterflies arrive earlier they will have no foodplants to lay eggs on. Linda
suggested that the butterflies were later arriving because of the cooler
weather and heavy rains we had during spring this year.
Ramblers always want to
know how you can tell when passion vine fruits are ripe. The answer is: when
they turn yellow. The day before today’s Ramble I found two ripe fruits and
placed them out of the way, but visible, on the other side of the deer fencing.
Today both fruits were gone.
Ghosts of Evolution: The
disappearance of ripe passion flower fruit has bearing on an idea mentioned in
previous Rambles: the Ghosts of Evolution hypothesis. First proposed by
biologists Paul Martin and Dan Janzen and later popularized by Connie Barlow in
her book, The Ghosts Of Evolution:
Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms, a
ghost of evolution is a plant that produces fruit for which there is no living
dispersal agent. An example is the softball sized fruit of Osage Orange trees. Giant
ground sloths or mastodons may have been the primary dispersers of the seeds in
this large fruit. They were big enough to eat the fruit with a single mouthful
and later defecate the seeds elsewhere. Both of these large herbivores became
extinct when humans arrived in the North America after the retreat of the
Pleistocene glaciers.
Barlow also suggested that passion flower fruit was a ghost of evolution. But the vanish of those passion fruits I put behind the
fence suggests that there are still animals around that can serve as seed
dispersers.
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| Blue Mistflower |
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| A Dirt-colored Seed Bug hiding among the flower heads of Blue Mistflower. |
Blue Mistflowers are a
good late season nectar source for many smaller butterflies, like the Skippers.
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| White Crownbeard |
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| Wingstem flowers |
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| Yellow Crownbeard Note the opposite leaf arrangement |
Identifying the wingstems:
The wingstems are the most abundant plant in the lower part of the power line ROW. All the wingstems are in the genus Verbesina
and can be recognized by the several thin, projecting ridges that run the length of the stem. In the southeast
there are three species of wingstems:
1. Wingstem (V.
alternifolia) with alternate leaves and yellow flowers;
2. Yellow Crownbeard (V. occidentalis) with opposite leaves and yellow flowers;
3. White Crownbeard (V. virginica) with alternate leaves and white flowers.
What keeps different species from interbreeding? To produce seeds most flowering plants need to be
pollinated. That can be done by using either the wind or an animal agent to
carry pollen from one plant to another. Most of the plants that have showy
flowers use insects to carry their pollen. But how can they make sure their
pollen gets to the correct destination? Obviously, other members of the same
species need to flower at the same time. Conversely, other species may be flowering at the same time, which risks wasting pollen by sending it to the wrong kind of plant.. But to minimize the chance of receiving
pollen from a different species, or wasting it on a different species flowering
schedules need to be different. For example, one species could flower in the
spring and another could flower in summer. Evolution has a hand in making this
happen.
When plants of different
species cross pollinate (hybridize) a range of things can happen. If they are
distantly related no viable seed is usually produced. The closer they are
related the greater the likelihood of seed being produced. Hybridization may result in fewer seeds being produced and/or the hybrid plants may grow poorly. In other words, the
hybrids may be less fit than either parent.
Now imagine two plant
species growing together in the same habitat with their flowering schedules
overlapping, one flowering a little earlier and one flowering a little later. When
each plant is flowering with just its own species it produces purebred seed. But
the plants that flower at the same time as the other species may produce hybrid
seed. If that hybrid seed doesn’t do as well as purebred seed natural selection
favors the plants that produce purebred seed. So the earlier-flowering
individuals of the early species will produce relatively more seed than the early flowers
that bloom later in the year. And selection also favors the later blooming plants of
the later blooming species Other things being equal, the flowering times will
diverge and, after many generations, the overlap in the flowering schedules
will be reduced.
Speculation: Something
like the hypothetical situation above may be operating among the wingstems.
Each of the three wingstem species begins flowering at a different time. The first to
flower is White Crownbeard, followed by Yellow Crownbeard and then Wingstem. By
the time that Wingstem begins flowering the White Crownbeard is finished and setting
seed.
Of course, there are
other ways that plants can solve the flowering time problem. For example,
they could share their pollinators by offering nectar at different times of the
day. You can probably think of other ways two species could come to share a
common habitat without producing a lot of poorly adapted hybrid seed.
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| Tick-trefoil fruits (AKA Beggar's Lice or Beggar's Ticks) |
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| Tick-trefoil flower; the large petal is the "standard" Note the nectar guide marking at the base of the standard. |
Tick-trefoil (Beggar’s Lice) is a member of the bean family (Fabaceae) and has three features that
indicate this membership. Each leaf is composed of three leaflets, the seed
capsule is shaped like a pea pod, but with constrictions between the places
where the seeds are held, and the flower has five petals, one of which, called
the standard, is large and conspicuous. The other four petals are smaller and
project forward, covering the stamens and pistil. Together, they are called the "keel." The nectary is at the base of
all the petals and there are two marks at the base of the standard petal that
point to its location. These marks are called “nectar guides” and it is thought
that they direct pollinators to the location of nectar. Additional marks,
invisible to the human eye, are found in the nectar guide. These are
ultraviolet marking and are visible to bees. They can be seen by humans only
with UV-sensitive film or cameras.
The other common name
for these plants, “Beggar’s Lice,” refers to a property of the seed
capsule. It is covered with microscopic hooks that adhere to clothing or hair
of passing animals. Avis told us that these seed capsules were the inspiration
for the development of Velcro.
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| Goldenrod |
Goldenrod and its galls
have fascinated biologists for years. A gall is an abnormal formation that
forms on a plant in response to the presence of another organism. The burls that
were seen on the Winged Elm in last week’s ramble could be considered a type of gall.
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| Goldenrod bunch gall (AKA apical rosette gall) |
The commonest gall
affecting Goldenrod plants in the power line ROW is a bunch gall, sometimes called an apical rosette gall. It is a cluster of tightly packed leaves at the top of a plant and is caused by a fly, a type of midge, that
resembles a mosquito but does not bite. Earlier in the year, when the goldenrod
is three to four feet tall, the midges emerge, mate and the females search for goldenrods. The female then lays an egg in the growing tip of the
goldenrod plant. Something in the fluid she injects with her egg or produced by the
larva when the egg hatches inhibits the elongation of the growing goldenrod stem, but
not its ability to produce leaves. The result is a plant that is capped by a
rosette of dozens of leaves about ½ inch high. The midge larva inside feeds on
this plant tissue, protected by the tight cluster of leaves. But the plant
doesn’t grow any taller. When infected with a bunch
gall the plant responds by activating adventitious buds lower on the stem.
These will develop into weaker side branches that ultimately bear flowers, but
not as many as an ungalled plant would have.
Researchers at Bucknell
University in Pennsylvania has revealed a clever behavior on the part of the
goldenrod. When the goldenrod reaches a height that will be attacked by the
gall-making midge it ducks! The top of the plant bends over like an inverted
“J,” effectively hiding the growing tip of the plant. These ducking goldenrods
avoid becoming hosts to the gall-making midge. Midges don’t live very long and,
after a week or so, all the ducked goldenrods straighten up and proceed to
develop normally.
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| Goldenrod spherical stem gall |
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| The fly maggot inside the Goldenrod spherical stem gall |
The spherical stem gall
is another gall sometimes seen in the garden, but it is less common than the
bunch gall. This gall is caused by a fly unrelated to the bunch gall and
develops as a spherical swelling in the stem of the goldenrod. The fly larva
overwinters inside the gall and then emerges in the spring. The size of the
gall influences the fate of the developing insect inside. If the ball is too
small parasitic wasps can drill through the wall and lay eggs on the larva
inside. So there is selection for the gall maker to make a larger gall. But the
galls are very conspicuous during the winter and are pecked open by chickadees
and downy woodpeckers to get the grub inside. These birds selectively choose
larger galls, producing a selective force for smaller gall size. Sometimes you
can’t win! The result appears to be the Goldilocks solution: the gall should be
neither to small nor too big, but just right.
(Note: in addition to
the birds, small boys named Jeff were in the habit of extracting grubs from
galls for fish bait in the winter. Ask him if he preferred the larger or
smaller galls.)
If you find goldenrod
galls interesting this web resource will
astonish you with the amazing number and diversity of goldenrod gall makers and
their parasites.
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| Velvet Ant female |
When we find Velvet
Ants it is usually in the power line ROW,
but that’s probably because they are more visible in the mowed grass paths. A
Velvet Ant is not an ant, it is a parasitic wasp. The females are wingless; the
males have wings but the color pattern is often very different from the
females. For many years the females and males were given different species
names for this reason.
The female wanders about
seeking the burrows of solitary bees and wasps. When she finds one she enters
it and lays an egg in each cocoon she finds. When the egg hatches the Velvet
Ant larva devours the host pupa. Entering a burrow where a wasp or bee might be
present could be dangerous work, but never fear – she has a thick, tough
exoskeleton that resists stingers. In fact, velvet ants are notoriously
difficult to pin for insect collections. Insect pins are very sharp but even
they have difficulty penetrating the exoskeleton.
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| Ants on the underside of a Rough-leaved Sunflower leaf. The two black insects (one in the center, one to the left side) appear to have been attacked. |
Ants: Another curious
find was a small group of ants on the underside of a Rough Sunflower leaf.
Usually ants will cluster around extrafloral nectaries but none were
seen on this leaf. Another common sight is ants tending aphids. They protect
the aphids from parasitic insects and consume the honeydew that the aphids
excrete. I didn’t see any aphids on the leaf. We saw nothing else until Don
zoomed in on his photograph which revealed two unidentifiable insects that
looked to me like they had been partially eaten. They were likely some kind of
sap feeding insect like aphids, but we couldn’t determine what they were.
Speaking of ants, Rambler Rich Kimmich
developed this topical spray to ease the effects of fire
ant stings and mosquito bites. He had this with him on the Sept. 13 Ramble and had
at least three opportunities to try it out on Ramblers who
stepped into fire ant nests. It seemed to give relief and is available in the
Gift Shop if you want to try it out.
Speaking of ants, Rambler Rich Kimmich
SUMMARY OF OBSERVED
SPECIES:
Bumblebee
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Bombus sp.
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White and Red Salvia
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Salvia sp.
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Marsh Ladies' Tresses
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Spiranthes odorta
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White Marked Tussock
Moth caterpillar
|
Orgyia leucostigma
|
Fall Webworm Moth
caterpillar
|
Hyphantria cunea
|
Rough Green Snake
|
Opheodrys aestivus
|
Gulf Fritillary
(caterpillar and chrysalis)
|
Agraulis vanillae
|
Blue Mistflower
|
Conoclinium
coelestinum
|
Dirt-colored Seed Bug
|
Family
Rhyparochromidae
|
Purple Passionflower
(vine and fruit)
|
Passiflora incarnata
|
Yellow Crownbeard
|
Verbesina occidentalis
|
Wingstem
|
Verbesina alternifolia
|
Virginia Buttonweed
|
Diodia virginiana
|
Tall Goldenrod
|
Solidago altissima
|
Yellow-striped
Armyworm
|
Spodoptera
ornithogalli
|
Dog Fennel
|
Eupatorium
capillifolium
|
Tall (Smooth) Beggar
Lice
|
Desmodium glabellum
|
Eastern Velvet Ant
|
Dasymutilla
occidentalis
|
Yellow-bear
caterpillar
|
Spilosoma virginica
|
Rough-leaf (Woodland)
Sunflower
|
Helianthus strumosus
|
Spiny-backed Orbweaver
|
Gasteracantha
cancriformis
|
Box Elder
|
Acer negundo
|
Maryland Wild Senna
|
Senna marilandica
|
White
Crownbeard/Frostweed
|
Verbesina virginica
|
Tall Thistle
|
Cirsium altissimum
|
