Saturday, August 20, 2016

Ramble Report August 18 2016



Today's Ramble was lead 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.



No. Attendees: 22

Today's reading was supplied by Rosemary. She intends to ramble in England in the near future, so she read a short history of the British Ramblers Association, followed by Bill Bryson's account of the famous (in Great Britain) Kinder Scout civil disobedience in his book, The Road to Little Dribbling:


 Kinder (it rhymes with "cinder") Scout isn't a peak, but a grassy plateau, visible in clear weather from Manchester and Sheffield, both about twenty miles away. That was the root of the problem, it seems. Workers in Manchester and Sheffield gazed dreamily upon Kinder Scout from their gritty neighborhoods and thought of it as their hill, the place where they could go for fresh air and spiritual refreshment at weekends, and for years they did. But in the 1920s, the Duke of Devonshire closed Kinder Scout to the public for the sake of his grouse shooting. This naturally bred resentment, and in April 1932 five hundred people, mostly factory workers, gathered at Bowden Bridge to undertake a protest walk across the duke's land.

Tipped off about the hike, the duke's gamekeepers were waiting and ordered the hikers to turn back. The result was a brief and rather endearingly ineffectual scuffle. One gamekeeper was knocked unconscious, probably accidentally, but there were no other injuries and the walkers swept past the gamekeepers and completed their march to the summit. The authorities, overreacting, arrested the group's leaders and charged them with criminal trespass. Five men were sent to prison for up to five months - an outrageously disproportionate punishment. The result was a wave of anger and resentment that went well beyond Derbyshire. The Mass Trespass (as it is now invariably written) became an iconic moment in the history of both class struggle and the British countryside. In other countries they fight over politics and religion. In Britain, it is over who gets to walk on a windswept moor. I think that's rather splendid.

Dale followed Rosemary's reading with a brief history of the origins of our Nature Ramblers; details can be read here.



Don took a minute to thank Rosemary for the fine job she did as Ramble photographer in the five weeks he was away.

Today's route: Due to the heavy rains last night (4.05 inches in the last 24 hours) there were several trees and a powerline downed in the Garden, making the natural areas a little hazardous. Because of these problems we repeated the route from two weeks ago (August 4), staying in the formal gardens. The morning sky was clear, so we hoped for butterflies and other flying insects.



At the first junction of the American South Garden we spotted two large orb webs, one high up between two trees, the other about shoulder level. These spiders, plus another seen later this morning, are Triangulate Orbweavers, named for the triangular mark on the back of the abdomen. This spider is frequently encountered in the garden and toward the end of summer they are large enough to produce very conspicuous webs. 
Triangulate orbweaver
The triangular mark can also be yellow


Web of the Triangulate orbweaver
One question that always arises when a web is seen stretching between to two trees is how did it get there? Did the spider start spinning a strand of silk up high and then walk down the tree to the ground and up the next ree, spinning a length of silk as she went? That seems unlikely, and it is, but the truth is even a little more surprising. The spider begins by moving to the end of a branch that is open to the surroundings. She lifts her abdomen and releases a strand of silk from her spinnerettes, letting the breeze pull it out of her body. The end is sticky and when (or if) it contacts a nearby object, like another tree branch, it will adhere to it. When that happens the spider attaches her end of the silk to her branch and walks along the newly established silken bridge line, spinning out another thread, and anchoring it to the other end. She then walks back on the double line to the center, attaches another strand of silk to one of the bridge strands and drops down the earth below, releasing another strand of silk as she goes. When she reaches the bottom she pulls down the descending strand, creating a triangle in the air. (The triangle is formed from the original bridge and the two sides of the second strand that was pulled downward.) The point where the single, vertical strand meets the apex of the silken triangle will be the hub of her web. She now climbs back up to the future hub and uses this scaffold to spin and attach additional radial anchoring strands. When there are enough anchoring strands she moves back to the hub and begins to spin the orb of sticky capture silk, moving from the hub in an ever increasing spiral until she is finished. She then carefully walks back to the hub, touching only the non-sticky anchor strands, and sits, waiting for her prey to blunder into and become stuck in the web.

By the way, these webs must have been spun after last night's rains stopped. An unprotected spider web can't withstand heavy rains like those that fell last night.



As we walked past the flower beds the most obvious thing we noticed was that there weren't any bumble bees. In fact, we only sighted one lonely honey bee visiting the blue Salvias, quite a change from two weeks ago when there were dozens of bumble bees all over the Salvia.



Some Ramblers saw hummingbirds visiting the hanging baskets on the walls of the conservatory.



Cypress vine; note the long, tubular corolla and lacy foliage
Linda pointed out a Cypress Vine with brilliant red, tubular flowers. This flower color and shape is typical of hummingbird pollinated flowers. It is in the Morning Glory family and has leaves that are pinnately divided into very fine segments, creating a fern-like impression.



We saw two lizards this morning, a Green anole and an immature skink (more about the skink later). Because there were a lot of questions about anoles I'm repeating a section of my post from August 4.



Common Green anole in its brown coloration

Common Green anole in its green coloration
The Green anole is sometimes called the Carolina anole or the American chameleon. All these common names, especially the last one, have been applied to the small, green or brown lizards (Anolis carolinensis) we saw today. It is not a true chameleon; they are lizards found principally in sub-Saharan Africa, Madagascar, southern India and Sri Lanka. They are much more adept at changing their color than our little anole. Our anole is limited to changing its color between green and brown and does not change color to match its background. Mature males have an extensible throat fan, called a dewlap, that is colored pink or red. It is usually displayed when another anole is entering the owner's territory and is thought to function as both a territorial and sexual signal. It's used to attract lady anoles and frighten away male trespassers. The dewlap display is usually accompanied by a series of jerky pushups, in which the front of the body is elevated and lowered several times in rapid succession. If the encroaching lizard is a male it may flee or engage in a fight that the territory owner usually wins, if they are evenly matched.



The pronunciation of "anole" is often a source of disagreement. I have heard many variations: 1) "uh-KNOLL," 2) "AN-ol," 3) "uh-KNOLL-ee," and 4)"AN-ol-ee." In fact, five years ago I asked an anole expert for the proper pronunciation. You can read the replies, mixed in with the origins of the word, here and here. The short version is simply this: you can pronounce it however you wish – there is no preferred pronunciation.



How Green anoles change color

The skin of anoles contains four layers of pigment cells. The lowest layer consists of cells that contain the dark pigment melanin. (Melanin is the pigment that produces a tan in human skin.) These cells, called melanocytes or melanophores, have numerous lengthy extensions that reach through the pigment cell layers above them. The melanin granules in the melanocyte can either be huddled together in the cell body below the top layers of pigment cells or dispersed into the long branches above the other pigment cells. In the first case the color of the anole is green; in the second, brown, the melanin pigment granules effectively covering the underlying pigment cells. The change in color is controlled by hormones, especially adrenalin and MSH (Melanocyte Stimulating Hormone). When excited or stressed the anole produces adrenalin and the melanocytes concentrate their melanin in the cell body, revealing the underlying green color. MSH has the opposite effect, causing the melanin to disperse into the cell branches, covering up the green color.



Why do Green anoles change color?

The conditions that cause Green anoles to change from green to brown and vice versa are complicated and not well understood. This post provides a summary of some of the studies that suggest how different social and ecological factors affect the color of Green anoles.



Immature skink; perhaps a Five-lined skink
but it could also be a Broad-headed skink or a Southeastern five-lined skink
We found a juvenile skink basking on the brickwork in the Herb & Physic gardens. A skink is a type of lizard that has smooth, overlapping scales that gives it a slick, shiny appearance. We can tell that this one was a juvenile because it had a dark body with five yellow lines and a bright blue tail. All the common skink species in the area look like this when they are immature. There are three skink species found in this area: 1) the Five-lined skink, 2) the Southeastern Five-lined skink or 3) the Broadheaded skink. The young of all three species look almost identical – they can only be told apart by looking at certain details of their scalation. To do that you need to capture the animal. As these skinks mature they gradually lose their yellow lines and the blue color on the tail. When they are mature the Broad-headed skink is larger than the others. The head of the sexually mature male is very broad and has a rusty orange color on its head at the back of the jaw. They are also more arboreal (tree-loving) than either of the other two skinks. The Five-lined and Southeastern five-lined are so similar at all ages that you have to have the animal in hand to identify them.

All skinks share an unusual characteristic: they can spontaneously drop their tail. The do this when they are threatened by a predator. The tail vertebrae have a fracture plane and special muscles that, when contracted, break the vertebra along that plane. The tail falls off, twitching violently, which attracts attention away from its owner. Muscles in the stub left on the lizard contract and reduce or prevent the loss of blood. The tail can regenerate but the new growth differs in appearance, so you can tell when a skink has experienced previous attacks by would-be predators.


Butterflies were in short supply today, probably because of last night's heavy rainfall. It may have caused heavy mortality or the butterflies were still chilled from the low temperature following the thunderstorms. We did see a Silvery Checkerspot, Eastern Tiger Swallowtail and Giant Swallowtail.


Silvery Checkerspot upper surface; at the edge of the hind wings is a row of black dots,
some of which have open centers -- a character that separates the Silvery Checkerspot
from the Pearl Crescent.


This Silvery Checkerspot shows the lower surface of the hing wing;
notice the rows of whitish to silver marks characteristic of this species.
(photo by Dale Hoyt)
The Silvery Checkerspot is hard to distinguish from a smaller butterfly called the Pearl Crescent. The under surface of the hind wings has a series of spots that are buff to silver in the Checkerspot. It is also larger in size, but that does not help if you're inexperienced or don't have the two sitting side by side. If all you can see is the upper surface of the wings the best character is the row of black dots on the margin of the hind wing upper surface. That row is surrounded by an orange field and at least one of the dots within the field will have an open center; i.e., it will be a tiny circle instead of a solid dot.

Giant Swallowtail nectaring on Mexican Sunflower


Other organisms:

Paw Paw fruits
The Paw Paw fruits are still intact but haven't changed color since the last time we checked. They are usually eaten by critters unknown (probably possums or raccoons) just before they ripen.


Long-legged fly (Dipter: family Dolichopodidae)
While looking for the Paw Paw fruits we noticed a tiny fly sitting on one of the leaves. This turned out to be a Long-legged fly (family Dolichopodidae, if you're interested). The larvae of the flies in this family feed on aphids, so, if you're not an aphid, you could consider them a "beneficial" insect.


Black-eyed susan vine (Thunbergia sp.)
Everyone was taken by the Black-eyed susan vine with its black centered tubular yellow flowers. It is unrelated to the "real" Black-eyed susan, which is in the sunflower family. The namesake vine is in the plant family Acanthaceae and is native to Africa, Madagascar and Asia.

Trifoliate orange -- wicked thorns!
Another Asian introduced species, Trifoliate orange, impressed everyone with its compound leaves consisting of three leaflets (hence the trifoliate name) and wicked, wicked thorns. The plant is cold hardy so the root stock has been used in grafting other citrus family plants that are more sensitive to low temperatures. While we were looking at this plant as passerby told us that in Africa people use it has a hedge to keep hippopotamus out of their gardens. I've been unable to corroborate this information, but it is plausible. The fruit of the plant is extremely bitter.

We visited the Sorghum patch again, but the heavy rains washed all the honeydew off the leaves so the hundreds of bees and wasps we saw two weeks again were all absent. Lacking this focus for our attention someone pointed out that the next row over consisted of corn. which gave us a chance to compare these two similar plants.
The most obvious difference between the two is that Sorgum does not produce "ears" like corn where the leaves meet the stem. Corn ears are really inflorescences of female flowers, each flower giving rise to a single kernel of corn. Remember your botany? The female part of a flower is the pistil, which consists of an ovary, a style and a stigma. The ovary contains the egg cell(s), the stigma is the surface where pollen lands and germinates and the style is the part of the pistil that the pollen tube grows through to get to the egg. What do these part correspond to when you get an ear of corn to eat: the ovary develops into the fruit we call the kernel of corn, the silk is the style and the stigma is at the end of each silk. A pollen tube has to grow through the silk in order to fertilize the egg cell and initiate the development of the kernel. The silk can be 6 inches long, a tremendous distance for the microscopic pollen to have to grow. 

Speaking of corn pollen, where does it com from? At the top of each corn plant a structure called the tassel develops. The tassel is an inflorescence of male flowers that produce the pollen. Corn is wind pollinated and the tassels have to produce a lot of pollen to guarantee that all the silks get at least one successful pollen tube.

The Sorghum plant has all its flowers at the top of the plant. It will produce seeds, but they will not be in ears. Unlike corn, Sorghum flowers have both male and female parts.

Growing on the benches by the Sorghum are a number of different lichens.  A lichen is a symbiotic association between a fungus and a unicellular photosynthetic organism, either a blue-green bacteria or a green algal cells. The fungal part wraps around the photobionts and protects them and supplies them with water and mineral nutrients. The photobionts supply the fungus with sugars that they make by photosynthesis. The lichens grow on surfaces, but are not parasites. They simply use the surface as a place to grow. For over one hundred years it was known that lichens consisted of these two components but very recently it was discovered that some lichens incorporate a third entity, a kind of yeast. How widespread this is remains to be seen.

Foliose, fruticose and crustose lichens
Lichens exhibit several kinds of growth forms. The three commonest are called crustose, fruticose or foliose. Crustose lichens are like crusts, growing flat against a surface; foliose lichens have a leafy structure, i.e., parts that are elevated and not in contact with the surface they grow on. Fruticose lichens resemble bushy or shrubby plants. The lichens growing on the benches exhibit all three growth forms.


SUMMARY OF OBSERVED SPECIES:

Triangulate orbweaver spider Verrucosa arenata
Ruby throated hummingbird  Archilochus colubris
Salvia Salvia sp.
Honey bee Apis mellifera.
Eastern carpenter bee Xylocopa virginica
Cypress vine Ipomea quamoclit
Hops Humulus lupulus
Carolina anole Anolis carolinensis
Silvery checkerspot Chlosyne nycteis
Black-eyed Susan vine Thunbergia alata
Common evening primrose Oenothera biennis
Tall ironweed Vernonia altissima
Paw paw Asimina triloba
Tiny golden fly Diptera: Dolichopodidae
Ginger lily Hedychium coronarium
Spiked wild indigo Baptisia albescens
Confederate rose Hibiscus mutabilis
Spiked wild indigo Baptisia albescens
Skink Plestiodon sp.
Trifoliate orange Poncinus trifoliata
Castor bean plant Ricinus communis
Sorghum Sorghum sp.
Corn Zea mays
Multicolored Asian lady bettle Harmonia axyridis
Various lichen species ?
Sourwood Oxydendron arboreum
Eastern tiger swallowtail Papilio glaucus
Giant swallowtail Papilio cresphontes
Mexican sunflower Tithonia rotundifolia
Rose of Sharon Hibiscus syriacus
 


 

4 comments:

  1. Excellently written and chock-full of interesting science.

    ReplyDelete
  2. Since I am unable to arrive at 8:00, I always miss the first 20 to 30 minutes of the ramble. I really appreciate the reports. They enable me to catch up on the readings and the first batch of interesting things the group comes upon. Thanks, always, "y'all" for leading the group and writing the report.

    ReplyDelete
    Replies
    1. In September we will resume starting at 8:30AM. I hope that will make it easier for you to attend. We always enjoy your presence!

      Delete

Post a comment