from the woods near Natchez, Mississippi, USA
August 1, 2004
The annual or "dog-day" cicadas have begun droning high in the trees lately and that's as good a sign as any that summer is getting on. Leona in the Missouri hill country tells me that walnut leaves up there are turning yellow. Around here the lower leaves of Winged Sumac are crimson red, though everything else, including the walnuts, remain lush and deep-summer green.
However, if you look closely at tree leaves you'll see that they're starting to show their age. Just about every one is splotched with fungal infections and has been nibbled on by bugs.
On the one hand it's astonishing that leaves have so many enemies beating up on them all summer, yet, on the other hand, you wonder what's to keep the fungi and bugs from just eating up everything. If a bug can eat leaf material, then why doesn't it eat the whole thing, or why aren't there so many bugs that all the leaves get eaten?
Of course sometimes that does happen. This spring a Black Cherry tree next to the barn had every single one of its newly emerged leaves eaten by tent caterpillars, and sometimes fungi do kill weakened trees. However, that isn't the way it commonly is. Usually fungi and insects are evident, but they don't overwhelm their host.
All plants, not just trees, have evolved ways to defend themselves. Among higher plants the main defense is often provided by chemicals inside the plants.
Buttercups with their pretty yellow blossoms in spring contain ranunculin, a toxin causing diarrhea and vomiting. Lily of the Valley contains convallarin, which causes irregular heartbeat. Leaves of the common yew planted around many suburban houses contain taxine, which can cause sudden death. For many other examples like this you can review the lecture notes for a class at the University of Maryland on "Poisonous & Allergenic Plants" at www.life.umd.edu/classroom/BSCI124/lec30.html
So, the forest with its current moist shadowiness appears to be enjoying a gentle repose, but in reality the woods is nothing but a war zone in which every organism is fighting for its life, and no one species can get the upper hand for long. If a plant evolves a toxin that succeeds in keeping all insects from eating on it, it won't be long (in the evolutionary context, maybe a few centuries) until an insect evolves a biochemical pathway enabling it to get around the new chemical defense, maybe even thrive on it, the way Monarch Butterfly caterpillars crave the otherwise poisonous alkaloid in milkweeds.
RECORD-MAKING COLD FRONT
Enhancing the feeling that fall is in the air, earlier this week a cold front stalled right atop us, making it feel more like October here than July, and it was wonderful. The National Weather Service in Jackson issued this special bulletin on Tuesday, the 27th: "The record low maximum temperature was broken today with a temperature of 79 (26° C) at Thompson Field. The previous record was 82 set in 1994."
I'm sure glad this cold front arrived in July and not in January.
GOURDS ON THE GARDEN FENCE
Each morning I can't wait to walk around barefooted in the chilly dew seeing how things have grown during the night. I'm always surprised by how big the eggplants have become, how high into the Loblollies my Moonflowers and Hummingbird Vines have twined, how many big, purple Morning-glory flowers are blossoming, etc.
The stars nowadays are the gourds. Last September on my yearly trip back to Kentucky a cousin with many kinds of gourd growing along a fence gave me some seeds, so this year I have a similar display. There are several kinds, some of them pretty strange looking. It's easy for a gardener to get hooked on growing novelty gourds.
The question arises as to whether all these fancy gourds are just different varieties of the same species, as with the cabbages (Cabbage, kale, Brussels sprouts, cauliflower and broccoli are all just horticultural varieties of a common wild ancestor, Brassica oleracea), or whether each gourd is a distinct, true-breeding species.
With gourds it's a mixed bag. In most of our North American gardens, our gourds arise from three species:
Yellow-flowered Gourds include a large number of vines producing small, colorful, ornamental fruits, including the ones known as Apple, Bell, Bicolor, Egg, Orange and Pear Gourds. The edible fruits of bush squashes and pumpkins are derived from the same species but from a different variety. The flowers of this kind of gourd, besides being orange-yellow, are large and funnel-shaped, and the vine stems bear sharp, scratchy, translucent hairs. The gourds are mostly less than 4 or 5 inches thick or long, and are typically unicolored or striped. You can see a variety of yellow-flowered Gourds at www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Cucurbita/b1261tx.html
Bottle Gourds produce fruits much larger than the above type, and the fruits mature to pale, tan hues. Instead of being mainly ornamental, Bottle Gourds were developed mainly to serve utilitarian purposes. Among my own Bottle Gourds is a long one with a constricted middle. In the old days people made bird boxes from them. Another is very large, probably developed for holding stuff. Among "Bottle Gourds" are those known as Dipper, Cannon Ball, and Bushel Basket. These are also known as "White-flowered Gourds." Besides having white flowers their vines are softly hairy, plus they have a musky odor. An identification chart showing the shapes of 23 kinds of Bottle Gourd can be seen at www.americangourdsociety.org/FAQ/types/chart.html
Luffa Gourds, whose dried, fibrous interiors can be used as sponges, have either yellow or whitish flowers. If you're not sure whether your gourd is a luffa, a technical way to distinguish it is that the luffa vine's male flowers appear in clusters (in racemes), not alone, as with the other groups.
Lots of other kinds of gourds exist, plus there are many of which you can't decide whether they're more gourd, pumpkin or squash. A huge amount of information and lots of pictures of gourds of all types is at the "Wide & Wonderful World of Gourds" page at http://waynesword.palomar.edu/ww0503.htm
A GOOD TIME FOR APHIDS
Right now many weeds have well developed roots and bodies, but haven't yet begun producing fall flowers. This means that toward the tops of the plants rapidly growing sprouts are succulent and full of sap. In other words, those new sprouts make perfect grazing grounds for insects such as aphids who insert their strawlike beaks into the plants and just sit there sucking up plant juices. Around the barn nowadays many horseweeds and goldenrods, standing about head high, have their tender shoots absolutely covered with aphids, sometimes known as plant lice.
On my aphid page (www.backyardnature.net/aphid_lc.htm) I make the point that each wingless adult female aphid can produce 50 to 100 offspring. A newly born aphid becomes a reproducing adult within about a week, and then can produce up to five offspring per day for up to 30 days! The French naturalist Reaumur during the late eighteenth century calculated that if all the descendants of a single aphid survived during the summer and were arranged into a French military formation, four abreast, their line would extend for 27,950 miles, which exceeds the circumference of the Earth at the Equator!
Aphids have very complex life cycles, some of which are described on my web page. These days the aphids on our horseweeds and goldenrods are all wingless females and they are all prodigiously producing babies which also are all wingless females. This baby-producing is all being done without the help of males -- no sex involved. It's a kind of asexual reproduction known as parthenogenesis. When cooler, shorter days arrive the wingless females will begin producing winged offspring, who will fly to another plant and eventually begin producing both males and females, who will then reproduce the usual way.
The ones having babies now are doing it in the most nonchalant manner. If you look closely you'll probably see some of them quietly sucking through their proboscis on one end, while a baby is being extruded from the other end.
Many of these aphid cities are also attended by ants who gather droplets of "honeydew" extruded from the aphids' rear ends. The aphids filter nutrients from their plant sap and constantly must rid themselves of the surplus liquid. Not all nutrients are filtered from the excreted liquid, however, and ants are glad to have it. In fact, sometimes the ants carry aphids to new places, and protect them from predators.
GREEN LYNX ON A RAGWEED
This spring when I saw that a Giant Ragweed was coming up next to the barn door I decided to not hack it down because I knew just how interesting Giant Ragweeds can be. Now the plant stands eight feet tall (2.4 m), grows inches every day, and hasn't even begun producing flowers. I like Giant Ragweeds for two main reasons: First, their vigor and simplicity of form please me aesthetically, and, second, every Giant Ragweed hosts a city of interacting organisms. Each morning with my magnifying glass I scan the big plant's leaves and stems, and always there's something new and interesting to see.
One of the most eye-catching discoveries this week was a fairly large, green spider (front feet to back feet 1¼ inches, 3.2 cm) known as the Green Lynx, PEUCETIA VIRIDANS. A page with several very fine pictures of a Green Lynx, including ones showing the large female eating a smaller male, the female guarding its egg sac, and masses of recently hatched spiderlings, is at http://mamba.bio.uci.edu/~pjbryant/biodiv/spiders/Peucetia%20viridans.htm
Green Lynxes, instead of producing webs, roam over vegetation or lie in wait and leap on prey. Technically they're not wolf spiders. Wolf spiders are members of the Wolf Spider family, the Lycosidae, and mostly hunt on the ground, though some may go into vegetation. Lynx spiders have their own family, the Oxyopidae, and typically hunt in vegetation. The 350 or so species in the Lynx Spider Family are mostly tropical but about 20 species occur north of Mexico. Among the northern species our Green Lynx is the most conspicuous and best known, though it's found only in the southern states. This is such a spectacular spider that hobbyists often keep them in terrariums. A Swede describes how to put together a spider terrarium at http://hem.spray.se/minax/skotsel/terrarie_e.html
Despite not building webs, Green Lynxes do produce silk, but they use it as draglines as they hunt -- so that if they fall from a leaf, they'll end up dangling at the end of their dragline and can quickly return to their position. Also their egg sacs are made of silk, and silk is used to anchor the egg sacs to plants. The female then guards the egg sac.
My Green Lynx stayed on the same ragweed leaf for three days, then disappeared. That clump of ragweeds also is home for two rapidly growing baby Green Anoles, so maybe that explains the spider's disappearance. You really deny yourself a good bit of drama in your life when you cut down a ragweed!
Back in the 80s, while wandering through the highlands of southern Mexico, I stumbled upon a small, backwoods hospital-clinic providing free or very inexpensive service to desperately poor Tzotzil-speaking Indians. The clinic, known as Yerba Buena, was operated by Seventh-Day Adventists. I wanted to support the clinic so I wrote a book about it, its staff and the Indians, and gave it to the Adventists. The understanding was that proceeds from the book would go to supporting the clinic, not proselytizing. The book was published and I'm told that some benefits arose from it. One benefit was that I got to know some really wonderful people, both among the missionaries and the local folks, and they are still among my closest friends.
I've now placed most of that book on the Internet, along with some interesting pictures. If you are curious about what it's like in very isolated Indian communities in extreme southern Mexico, please take a look at the site. I think you'd be especially interested in a trip I took with some student nurses and a tooth-pulling preacher to the Tzotzil-speaking village of San Lorenzo, a full day of hard hiking off any paved road. That story is told in Chapter 48.
The new Yerba Buena site is at www.mexicanmercados.com/yb/index.htm
CONSERVATISM & LIBERALISM IN NATURE
This week's thinking about the conflict between trees who use chemical warfare to protect their leaves, and the bugs and fungi who attack those leaves, got me thinking about conservatism and liberalism in nature. Here's how that thinking went:
All of nature flows in a great river of ever-evolving, profoundly experimental and somewhat romantic liberalism, yet within this river of liberalism occur innumerable eddies in which the local status quo is more or less conserved, and, when people are involved, mythologized.
For example, the flow of evolution of life on Earth toward ever greater complexity and interconnectedness is quintessentially liberal, but the species themselves represent conservative, fairly static expressions of local ecological niches (Species evolution appears to proceed in "jerks," not gradually, as Darwin originally supposed). Similarly, the lifespan of an individual human can be seen as a liberalistic gushing forward, beginning in a self- absorbed, ignorant state and maturing into ever more broad-mindedness, and concern for the larger community. However, the society-imposed routines, prejudices, and unquestioning allegiances to established power structures, which basically define a person's identity and facilitate the accumulation of material wealth, are fundamentally conservative in nature.
You can see that I'm thinking in terms of classical conservatism (the idea of conserving the status quo, of being traditional) and of classical liberalism (embracing change, diversity and experimentation). Politicians often depart from these ideals for their own short-term gain, and this is never pretty. For instance, there's nothing conservative about Bush's deficit spending, and there's nothing liberal about Kerry's voting to make war in Iraq.
I am convinced that in the broad scheme of things conservatism and liberalism are of equal importance. In the absence of liberality anything becomes like a crystal: Comfortable and beautiful, maybe, but forever stuck being the way it is right now. There are no currents of creativity, no blossomings, no births and rebirths, no magic anywhere. Yet, without conservatism, chaos reins. There's such roiling, undisciplined confusion that nothing can take hold, nothing substantial can ever be produced, and there's no stable perch from which to admire the rest of Creation.
Therefore, as always, the trick is to follow The Middle Path. Do as Nature does, and artfully and lovingly mingle the two opposing inclinations. The forest follows the Middle Path when its liberal impulses send forth a great diversity of highly mobile, fast-reproducing and thus fast evolving bugs and fungi to consume the leaves of firmly rooted, slow-changing, trees. But nature protects its conservative components by granting them powerful defenses of their own. Because of this Middle-Path approach, the forest survives and itself continues to evolve and grow.
Battle-worn, fungus-splotched, tattered leaves are expressions of an ongoing, very messy but very beautiful working-out of the Creator's ever-contending conservative and liberal impulses.