Wisdom of the spider

The mornings have been cool and misty this week and I have noticed webs on the fence wires on more than one occasion. Within an hour or so the dew evaporates as the air warms. The breeze hastens and this dismantles the laborious work of the night before. I like the image below. I like the way in which the dark parts of each dew droplet are highlighted in the upper half of the photo and how the light parts of each droplet are highlighted in the lower part of the photo. I like the way in which the inner-most hub looks like a densely populated solar map, complete with sun and with six planetary objects and their associated moons. The business of constructing a web such as this is a fascinating one. It involves the formation of a simple infrastructure comprised of drop lines, a perimeter, and a series of spokes which radiate from the center. Once these elements are established the spider spins an auxiliary spiral of non-sticky threads from the inner hub to the perimeter of the web. The animal then turns and deposits a sticky, capture spiral, using the auxiliary spiral as scaffolding along which to negotiate the web and as a guide. Once the web is finished the spider travels about by moving along the radial threads and traversing the auxiliary spiral. Unwary prey are caught by the sticky elements of the capture spiral. As I thought about the cognitive power needed to carry out this sort of construction I wondered about the size and complexity of the brain of a spider. I was surprised to learn that, for their size, spiders have some of the largest brains of any organism we know. Workers at the Universidad de Costa Rica and at the Smithsonian Tropical Research Institute showed that the central nervous system of the smallest spiders occupy nearly 80% of their total body space, including 25% of the volume of the legs. They suspect that very little spiders might be mostly brain. Haller’s rule predicts that as body size goes down, the proportion of the body taken up by the brain increases. Human brains represent just 2-3% of body mass. The brains of some of the tiniest ants represent nearly 15% of their biomass, and some very small spiders are much smaller than ants. [The preceding facts were taken from a 2011 issue of Smithsonian Science.] Something called an encephalization quotient measures the ratio between actual brain mass and that predicted for an animal of a given size; it is thought by some to reflect cognitive ability or intelligence. By this measure, the Jumping Spider is recognized as having the highest EQ among invertebrate animals. Consider, for a moment, that the reason we are quick to marvel at the ability of a spider to create such a structure as intricate as a web is because we can’t imagine doing it ourselves, on whatever scale, within an hour, and at least once each day. Let alone creating the silk with which to build the construction, let alone determining whether a leaf or a tiny insect, or a dangerous wasp or a preferred prey item has encountered the web by sensing the vibrations which travel the signal line to highly sensitive legs. Marvel at that for a moment and then consider where you’d like to place the spider along the entirely fictitious Great Chain of Being!

web

A story of authenticity, in a nut shell

I think that what most kids know about where chicken comes from is that somehow it appears in the store wrapped in plastic. I wonder what kids know about where Chestnuts come from. Do they form naturally in cans, jars, or plastic sleeves? Do they simply arrive at the grocer’s to be nicely arranged alongside walnuts, pecans, and pistachios? The answer, of course, is that chestnuts grow on trees, they are nuts in both the culinary and botanical sense. Technically, a nut is a fruit composed of a hard shell and a seed. Botanists also require that a nut be indehiscent, meaning that the shell does not open to release the seed. But, you correctly point out, Chestnuts are released from the burr. I can only observe that this business of botanical labeling is a bit of a lawyer’s game. While reading up on the definition of nut I discovered that many culinary nuts are actually seeds (such that Brazil nuts are seeds of a capsule while Walnuts, Pecans, and Almonds are seeds of drupes). In any case, the photo below shows a burr of a Chinese Chestnut releasing its precious contents. You may know something of the history of the American Chestnut (Castanea dentata); it was all but eradicated from the eastern U.S. by chestnut blight (a fungus, Cryphonectria parasitica) which was accidentally introduced, from imported nursery stock, around 1900. By 1940 an estimated four billion trees had been lost. Resistant varieties of Chinese Chestnut (Castanea mollissima) were introduced and are now quite common. For nearly a century, scientists have applied the tenets of transmission genetics and of artificial selection to breed fungal resistance into stocks of remaining American Chestnut. You may check on the progress of the American Chestnut Restoration Project. By all accounts it has met with some success.

The blight resistant American Chestnuts are currently two years old and have survived their first growing season after being moved into the forest. They are approximately four feet tall. Two of the blight resistant trees flowered in this first year, a significant measure of advanced maturity. They were examined in September 2009 and the survival rate is above 90 percent. The trees appear to be healthy.

I wonder if any of you are asking Why should anyone care about a single tree species? Surely there are lots more out there. There are many answers to this question, I will offer three. The first is that the American Chestnut was here first and as such is entitled to exercise its privilege of squatter’s rights. It was not driven to the edge of extirpation by a natural infection, it was nearly lost due to the human importation of another species which harbored a deadly fungus. [Some would argue that humans are just as natural as fungi. I agree except for the little bits about ships capable of global navigation, the internal combustion engine and all the rest required to transport a pathogen across more than 5000 mile of open ocean from Asia to North America.] Through no fault of its own the endemic was attacked as a direct result of human activity. The second reason I can think of relates to the dynamics of ecosystems. I believe that we humans like to think that we know quite a bit about how ecosystems work and how they respond to perturbation. Although the science of Ecology has been recognized for more than a century, I do not believe that scientists, even those with supercomputers and algorithms, have come close to knowing how ecosystems respond when disrupted. This must be so because the lifetime of an ecosystem must be measured in thousands or even hundreds of thousands of years. What can we hope to learn about the response of an ecosystem over a span of even a century? Given the uncountable and unknowable number of organisms that were dependent upon the American Chestnut, its loss must have been, is still, and will continue to be significant in ways that we cannot know or measure. Rather than wait to learn of the consequences of its loss, I suggest we would be better advised to do what is required in support of its restoration. And, finally, I think it’s important to bring the American Chestnut back for the sake of authenticity. To simply supplant one species with another is not the answer because this does not restore the forest to its original state. S. J. Gould, when writing about the various guises of authenticity, wrote … The real and the replica are effectively alike in all but our abstract knowledge of authen­ticity, yet we feel awe in the presence of bone once truly clothed in dinosaur flesh and mere interest in fiberglass of identical appearance. So, yes, lots of us Tree Hugger Environmentalists worry about losing even a single species, for the loss lessens the authentic nature of our environment. A woodland landscape populated with a suitable replacement would be a lesser woodland indeed.

Nut

(50,000) Windows to the soul

One of the things I find most interesting about all insects, and not just this highly cooperative grasshopper that I happened upon while walking a tomato field a bit ago, is their compound eyes. We say that these are compound eyes because each is composed of thousands of photosensitive units called ommatidia (the diagram shows 15 of these forming part of the surface of the eye). Light enters each ommatidium through a cornea (labeled lens in the figure) and this is focused by the crystalline cone into a beam which enters a narrow tube called the rhabdom. The rhabdom is surrounded by retinula cells that generate electrochemical signals which pass along axons which are bundled to form the optic nerve, and this forms a direct connection to the brain. Contrary to popular belief, insects do not see a myriad of repeated images, akin to the wall of flat-screen televisions one encounters upon entering any well-supplied electronics store. Instead, each ommatidium forms an image of one tiny region of the animal’s visual field; all of these are then processed to represent the immediate visual environment. Because the cornea is fixed and cannot be focused, the resulting image isn’t highly resolved (the image of an insect’s view-of-the-world included below shows a stream, a near shore and a distant treeline). This arrangement is best suited for discerning movements as they occur across areas of contrast. The eyes of a horsefly, however, each with 50,000 ommatidia, can form a much more detailed picture of the world. Notice also that the grasshopper has a dark spot in the shallow depression between the antennae and also a spot between the right antenna and the right eye (there is a corresponding one on the animal’s left which is obscured by the antenna there). These are also organs of photoreception, ocelli, which are not as complex as the compound eyes and the function of which is limited to the discernment of light and dark. Finally, the title to this post begs the question of whether insects have a soul. I’ll get back to you on that one.

Bridges

I recently wrote about a walk we took the other day and mentioned that I had a bit of an adventure. The water surrounding the bridge support on the left (which I called an abutment but which I’m not sure isn’t more correctly a cutwater) doesn’t look all that deep, does it? I can tell you, from very personal experience, that it is. Or, at least it was deep enough to saturate me to the armpits as I made my way to the cutwater itself. Do not worry, my camera pack was well above my head during the traverse. At first I was going to post the image alone and then Joanna observed that the photo of the fallen log, taken just a few minutes after my swim, was also an image of a bridge. As part of the Pine Creek Rail Trail the steel truss crossing allows hikers, walkers, bicyclers, and runners to move from one side of the creek to the other. As for the bridge on the right, I can imagine any number of creatures, small and not-so-small, taking advantage of the placement of the log to negotiate the distance across the water. If you look closely, you may note that these images have something else in common. Both provide nice examples of specular reflection such that you can see the bridge, trees, and sky reflected in the water in the image on the left, and trees and sky in the image to the right. Interestingly, both also demonstrate what happens when the direct rays of the sun are blocked and objects are then illuminated by incidental light. This has a somewhat disorienting effect, making the viewer question points of spatial reference.

Peregrinations

Although the day was supposed to be showery, we woke to clear skies with but a few thin wisps of cloud; there was work to be done. You may remember a post which told about a clutch of eggs that our Speckled Sussex had hatched. Those birds are now grown and one of the harsh realities of farm life is that not all of the animals that arrive at Pairodox may stay. We let the hen set because the laying flock was aging a bit and, with winter coming on, it was a good time for one or two replacements. The hen managed to fledge eight peeps, four pullets and four cockerels. Four was a good number of girls but four boys was four too many. We discussed it over coffee and decided to conscript a back-up rooster. That meant we had three cockerels whose names instantly became surplus, supernumerary, and superfluous. Having emptied my cup I heated water to fill our largest kettle, sharpened two knives, and gave the dairy sink a good wash. Ten hours later I sat at the kitchen table, the rich aroma of chicken-at-a-boil suffused the first floor and was working its way upstairs. As a reward for our efforts we took to the creek at Ramsey. Joanna and Mr. Darcy hiked the trail to the south. My camera and I took to the creek bed. Because I thought I might do a bit of wading, I had worn shorts and sneakers. My point of entry was immediately adjacent to one of the steel truss bridges I have so often talked about. There were two anglers in the water, one was fly fishing and the other was using a worm-and-bobber. I asked how deep the water was between where they were standing and the near abutment. They did not know but agreed that I might be able to get to it over that way. Joanna walked back over the bridge about an hour later and shouted down, Decided to take a swim I see. Getting to the abutment turned out to be quite the adventure, suffice it to say everything was wet save my camera pack which I had held above my head during the traverse. Once out of the water and back on the trail Joanna showed me the way to a small pond. Although clouds were gathering and the understory was muted, the sun showed briefly to illuminate the shallows. I’m not often a fan of such photos but this one seemed to have a disorienting bit of depth, nice color, and a sense of movement that I liked. The Equinox will happen tomorrow and fall color is beginning to blush in the high hillsides. It will be breeding season soon and the sheep are restless. The Toms are maturing, awkward, strutting, gawky. The crops have dried down and await the pickers, choppers, balers, and combines. Evidences like these are bold and cry out the change; others are barely perceptible, but if you stop and listen you may note whispering among the trees. This is the time that things end their preparations and turn inward. Many would say autumn is the time that creatures prepare for winter. If things are not prepared now, the winter will be short, for they will not survive. These realities are not bad, or harsh, they are what they are. Why disparage the seasons and the challenges they represent? This Earth will continue to spin through its orbit, winter will come and it will go, and I will soon be writing about rain and about all good things green and growing.

What the nose knows

Here are a couple of images of a local tomato harvest that I thought you might enjoy. This field is across the street from tomatoes I showed you last week and immediately adjacent to sunflowers I featured here a month ago. The image of the harvester was taken as workers began to work the field a week ago and that of the bin was taken just the other day. I have often thought that it would be nice if someone would develop a technology that would allow you to smell aromas associated with pictures displayed on your computer monitor, tablet, or smartphone. If such a technology did exist and you were to click the image to the right, you would sense the rich aroma which emanated from the transport bin. The load was heavy and fruit at the bottom was getting a bit squashed. When I stood still I could hear the drip, drip, drip of sweet streams of fluid. Sweet, but not overpowering. The scent wafted up my nostrils and seemed to settle in that place, adjacent to the nose bridge and just below my eyes; that place where the pads of your glasses sit. As I continued to breath, the aroma matured as chemical signals steeped in the moistened walls of the sinus. Smell became taste as a cavalcade of electrical impulses traveled to my brain and from there to my parotid, submandibular, and sublingual glands. Almost instantly I was salivating. I shook off the sensory barrage and captured a few images. Forgive me for continuing with a comparatively unpleasant story, but I must report that I experienced a similar sensory phenomenon the other morning, though with a very different outcome. I was driving to town when I was assaulted by the odorous emanation of an as yet unseen, but well known, source. If you’ve ever wondered about such things you may be interested to know that the highly noxious smell produced by skunks may be sourced to a number of chemicals produced by the animal’s scent glands, mostly thiols (sulfurous mercaptans) and their thioacetate derivatives. The enclosed space of the cab filled with scent about a half-mile or so before I saw the offending (but unfortunately dead) animal in the middle of the road. Rather than causing me to salivate, the physiological cascade made my eyes water. I was just a bit disgusted when I realized that, in the same way that a sweet chemical mélange allowed me to taste tomatoes, this offending onslaught made me feel as though I was tasting the (literal) wretched secretion of the skunk. As soon as I was upwind, and though the morning was cold, I opened both windows to flush the cab. End of story.

Harvest2

Harvest

The pesticide and the honey bee

We’ve got several pear trees on the farm and the two oldest have very heavy fruit set this year. We had a peach tree that was similarly prolific and collapsed under its own weight. The ripening pears shown here are covered with what looks like a bit of rust, fungus; our apples are gnarly and nearly all sport one or a few holes, evidence of insect oviposition to provide newly hatched larvae a ready supply of nutrients. We could easily spray our trees with any of a variety of fungicides and pesticides but we do not, for a couple of reasons. First, we worry about chemical residues on the fruit that we eat and preserve. And second, although the matter has yet to be settled incontrovertibly, there is increasing evidence that fungicides and especially pesticides, most notably those called neonicotinoids, may contribute to Colony Collapse Disorder (CCD) which effects honey bees across the country and around the world. Honey bees are critically important pollinators of fruit and nut crops and it has been estimated that they are responsible for more than $15 billion in increased crop value each year here in the United States. That number increases by an order-of-magnitude when one considers potential global declines in crop productivity due to losses from CCD. The primary symptom of CCD is the nearly complete abandonment of hives by adult bees. What’s been so puzzling about this is that symptomatic hives have a live queen, plenty of capped brood (developing young), and lots of honey and pollen. Workers simply disappear. Where they go, nobody knows. Research to discover the cause or synergistic causes of CCD has been intensive. Possible primary culprits are fungal infection, mite parasitism, viral infection, immunosupression, and the toxic influences of both fungicides and pesticides. Several recent studies have shed light on the relationship between exposure to neonicotinoids (neuro-active insecticides like Imidacloprid and Clothianidin) and declines in managed bee populations. Based upon the strength of such studies the Canadian government announced a partial two-year ban on neonicotinoid pesticides in 2014. The year before the European Union adopted a two-year restriction on the use of neonicotinoids. There is a petition at Change.org which calls upon the Canadian government to ban these substances, outright. Here in the states beekeepers have allied with the Pesticide Action Network to petition the U.S. Environmental Protection Agency to suspend registration of neonicotinoids. To distill yet another of my very lengthy preambles, we have never sprayed our fruit trees, ever. Nearly all of our apples are scabby, the pears are scaly, and the peaches never, ever, look like anything you would want to pick from a supermarket shelf. If any particular piece of fruit is too-far-gone, we simply toss it for the deer and other visitors to the farm. Anything with a blemish or two, or three, finds its way to the kitchen where we have lots of very sharp knives. There are few imperfections which cannot be removed with a quick flick of the wrist. We do not care to produce pretty fruit, but we do care about the potential effects of toxins which would be released into the environment if we were to spray. In particular we worry about honey bees and the relationship between environmental toxins and CCD. We really do, and so should you. Is the cosmetic appeal of the fruits you purchase and consume really worth it?

Pear

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