Showing posts with label damselfly. Show all posts

End of October

Late October, 2015

The year that our sixteen year old Henry David Thoreau entered Harvard College, the German explorer and naturalist Prince Alexander Philipp Maximilian zu Wied-Neuwied worked his way to the edge of the American frontier, studying Indians, plants, animals, geology, and just about anything else he came near. Maximilian concluded his American explorations a year later and eventually published the account of his travels (the London edition came out in 1843, two years before Thoreau went to live at Walden Pond).

While Thoreau was still at the Pond, he began studying Indians as, perhaps, a way to connect to his idea of The Wild. This was his primary interest for the rest of his life. And as he poured over the Harvard library’s collection of books on native Americans, Thoreau kept detailed notes (his twelve Indian notebooks run somewhere around 3000 to 4000 pages). One of the books he eventually found was Philipp Maximilian’s. And I can’t help but imagine Thoreau’s heightened interest in this intelligent explorer’s account of all things Indian and all things Nature.

All of this is a dreadfully boring lead-up to our observation last week of what is for us here at The Creek a new flower: Helianthus maximiliani, the Maximilian Sunflower. Right. The idea is that our German friend encountered this native to the Great Plains on his explorations, and so he gets his name attached to the plant’s binomial name (along with several other plants and animals).

The generous Project Gutenberg has put online some of the writings of Maximilian. For those at all interested in early 19th Century naturalist writing or amazingly detailed firsthand accounts of Indians, these links would be hard to beat:

https://www.gutenberg.org/files/38784/38784-h/38784-h.htm

https://www.gutenberg.org/files/48235/48235-h/48235-h.htm

Helianthus maximiliani,
Maximilian Sunflower

A few days back (Oct 21), I squatted near the shallow yet quickly running piece of Creek about 30m upstream of the Pool. There, on a foot-wide stone half-submerged, loads of damselflies were perched or hovering in their famous reproductive posture known at the wheel or the heart. The male has sought out his mate and, perhaps while in-flight, grabbed her thorax right behind her head with the clasping structures of his tail-end. She then swings her tail-end back under herself and forward to a segment of the male’s tail where he has prepared his sperm for her taking. The pair will remain attached as the female deposits her eggs, generally into plant material under water or near the water surface. The whole time, the male (still grabbing her thorax with his tail claspers) is guarding the process from rivals, helping the pair to fly here and there (freeing up female energy so she can focus on egg-laying), and sometimes balancing himself at the water’s edge while his mate remains underwater to deposit eggs.

Depending on the anthropomorphic bent of the human observer, it’s a process that involves beauty and ugliness. And absurdity. Three days ago, healthy damselfly eggs by the hundreds were inserted into Creek plants with the hope of filling this stream with larvae and other flying generations. But last night the rains began in earnest. When I looked out the windows this morning, I could not even see the Creek, it was still so low from our drought. But no less than ten minutes later, it was churning with white foam and tree limbs, spanning almost a hundred feet in width. Flash. Flood. And all those countless damselfly eggs somewhere down in the Colorado River and on the way to the Gulf. Many of the larvae that have attached themselves to the bottom of larger stones will emerge here again in a few days. Those that attached themselves to stones smaller than a boulder will also find themselves in the bellies of River fish soon.

But when I think of what a single damselfly of a mated pair had to go through just to be washed away, my anthropomorphic mind cannot un-conclude that the whole show is absurd. The female herself had to feed and fight underwater for a year to three years as a nymph. Then she emerged one sunny morning and pulsed fluids through her newly expanding wings, morphing into the flying wonder we associate with these and similar waters. And then the quickly maturing process, the formation of eggs, the mate-clasping, the air-borne copulation, and the final and unlikely placement of tiny eggs into calm waters beneath my gaze. Now, though. The torrential loss just seems absurd.

And other images...

Praise

Don't think of it.

Vanity is absence.

Be here. Here

is the root and stem

unappraisable

on whose life

your life depends.

Be here

like the water

of the hill

that fills each

opening it

comes to, to leave

with a sound

that is a part

of local speech.

(Wendell Berry, The Country of Marriage)

Early May

Constant birdsong, summer tanagers unafraid of our presence in their woods, cool rains, smell of distant burning juniper, giant walking sticks preying on others within the orchard trees, and a Creek that changes daily. Waters are pulled by gravity, ever shifting shapes and humbly re-forming their ways according to the most immediate environments: faultline, hillside, boulder-face, fallen limb, fish scale, strider-leg, or crystal-housed diatom. The waters' devotion to impermanence is reflected in the effect it has on all else, as well, for the humility of waters is balanced by the unrivaled strength of its substance.

Under heaven nothing is more soft and yielding than water.
Yet for attacking the solid and strong, nothing is better;
It has no equal.
The weak can overcome the strong;
The supple can overcome the stiff.
Under heaven everyone knows this,
Yet no one puts it into practice.

(Lao Tzu, Tao Teh Ching, Chapter 78)

Insex

. . . and so it goes.

Back to the Creek as it looked the first week of May (2012). Since then, we have felt several inches of rain, and the waters have turned a muddy torrent.

Waters

School of carp

Fearless jumping squirrel

Disintegration

Decomposing shale on the banks of the Creek

My Favorite Tree (with chomped leaf, here)
American Sycamore (Platanus occidentalis)

Our Creek represents the "frontier" for the American Sycamore

Andrew Wyeth's depiction of the tree

Hunger

Cultivated blackberries

Light of Wing

Gray Hairstreak (Strymon melinus)

Great purple hairstreak butterfly (Atlides halesus)

One species of sphinx moth (family Sphingidae)
feeding on horsemint (genus Monarda)

More nearly resembling a hummingbird than our usual image of a moth, this family of insects feeds on nectar by hovering at one flower and then quickly darting off to the next (they can fly up to thirty miles per hour, faster than nearly all other insects). Such behavior (hovering in front of a flower to draw upon its nectar) is known to exist in only three groups of animals: bats, hummingbirds, and this family of moths. Notice the extremely long probosces of our species here.

Life is short. Only ten to thirty days long. Fly fast, sweet-tongued sphinx of our creek-side flower meadows.

And rains.

Gay Damselflies and Hoses Up a Hillside

From out of the Pond, water pumps up the hillside.

Three (3 1/2?) pairs of damselfly doing their thing near our submerged water pipe.

So the following excerpt was too good not to reproduce again here:

Damselfly Mating Game Turns Some Males Gay

James Owen
for National Geographic News

June 21, 2005

Disguises used by female damselflies to avoid unwanted sexual advances can cause males to seek out their own sex, a new study suggests.

Belgian researchers investigated why male damselflies often try to mate with each other. The scientists say the reason could lie with females that adopt a range of appearances to throw potential mates off their scent. In an evolutionary battle of the sexes, males become attracted to a range of different looks, with some actually preferring a more masculine appearance.

The study, published recently in the journal Biology Letters, says such evolutionary selection pressures could also explain homosexual behavior seen in males of other animals whose females assume a variety of guises. Such "polymorphic" species are seen in dragonflies, butterflies, hummingbirds, and lizards.

Female blue-tailed damselflies (Ischnura elegans) assume different color forms, or morphs, in adulthood: green-brown, yellow-brown, and blue. The blue form closely matches the male in both body coloration and pattern.

The study team found the sexual preference of male damselflies was influenced by the company they keep. Males that were housed together before being introduced to females tended to seek out their own gender afterward. But males kept in mixed-sex living quarters later preferred all three female forms when choosing a mate.

This suggests male damselflies are likely to become attracted to other males only when females are absent or scarce. Yet a minority of males still showed an innate preference for male mates.

The team's findings were reflected in mating behavior observed in the wild, says study author Hans Van Gossum, an evolutionary biologist at the University of Antwerp, Belgium.

Van Gossum says around 17 percent of males in wild populations appear to favor same-sex pairings, while about one in six males in the lab experiments showed the same tendency despite exposure to females. "This behavior can be considered homosexual," he said.

Sexual Selection

But why should any males choose to mate with each other instead of with females? Such behavior apparently goes against theories of sexual selection, which predicts the optimization of reproductive success. Homosexual damselflies, however, aren't going to sire too many babies.

Homosexuality has been recorded in a wide range of animals, including beetles, sheep, fruit bats, dolphins, and monkeys. In many such cases explanations have been put forward to explain this behavior.

Consider, for example, the beetle known as the sugarcane rootstalk borer weevil. U.S. and Israeli researchers suggest the reason why females of the species mount other females is that the behavior attracts big males with good genes. Puny males seem to shy away from such antics.

Female Japanese macaques also engage in intimate sexual acts with one another. U.S. primatologist Amy Parish and other researchers say female macaques may enhance their social position and form alliance partners through such intimacy which in turn can boost breeding success.

Van Gossum and his colleagues propose a new explanation for homosexuality in animals like the blue-tailed damselfly. When males face strong evolutionary pressures to be flexible about their idea of what a female should look like, males may end up also fancying their own sex.

Males damselflies need to be adaptable because their female counterparts are adaptable. Numbers of the three main female color forms, or morphs, fluctuate over time.

Van Gossum, the study author, says most researchers agree such polymorphism most likely results from sexual conflict, with females evolving traits to avoid excessive harassment. While plenty of sex might suit male damselflies, this isn't the case for females.

Joan Roughgarden is a professor of biological sciences at Stanford University in California. She writes, "Copulation ranges from over one hour to over six hours, averaging three hours. While a long copulation might seem like great fun, this can waste a whole day and be too much of a good thing, especially if carried out day after day over a life span that is only a few days long."

Roughgarden adds that female damselflies collect all the sperm they need to reproduce from a single mating.

Aviodance Tactics

"Males go for quantity and females for quality," Van Gossum said. "As a consequence, females may wish to avoid excessive male attention. One way of doing so is by looking different from what a male thinks a female to be."

The blue female form may accomplish this by mimicking the appearance of males. But Van Gossum says an alternative theory is that male harassment also leads to other morphs.

"The minority female morph in a population"—whether blue or another form—"is the one that benefits, by receiving less male harassment," he added.

In turn, it's likely that males have developed a flexible "search-image" that matches the majority female fashion of the day. This boosts a male's chances of finding a mate.

"Males with a search-image that can be changed if the minority female morph becomes the majority morph are probably out-competing males that are less flexible," Van Gossum said.

Such flexibility may also lead to genuinely homosexual damselflies.

Van Gossum says such behavior could arise when a male is still young. A preference developed in male damselflies before reaching maturity, he says, is probably less prone to change in later life.

The Belgian researcher adds that evolutionary pressures that shape damselfly mating behavior may also explain homosexuality seen in other male animals, including butterflies and hummingbirds, whose females similarly adopt a range of colorful guises.
http://news.nationalgeographic.com/news/pf/48026386.html

This excerpt is also too good not to copy and paste:

"Damselflies, like all odonates, have a very interesting breeding system. Before they actually copulate, males and females of many groups spend some considerable time in physical contact with one another, presumably in an effort to assess their potential mate. . . . This physical contact is made by the male clasping the female's thorax with the four terminal appendages on the end of his abdomen. [Note in our photograph above each male holding its potential mate with its terminal appendage (and in the one somewhat more interesting case, the male holding the other male's abdomen.]

"The male's terminal abdominal appendages consist of two superior cerci and two inferior paraprocts. The [left] figure [below] is a computer generated model of the tenth abdominal segment of a male E. ebrium viewed from the posterior. These four appendages grasp the female's thorax while they are in tandem. The [right] figure is a computer generated model of the females thorax viewed from above. The male's paraprocts contact her prothorax and the male's cerci fit into the two plates on the anterior surface of her mesothorax - the mesothoracic plates. These mesothoracic plates are thought to be used by the female to assess the species identity and potentially the suitability of the male that is grasping her in tandem.

"Field studies have shown that females discriminate among males based on cerci shape (Paulson 1974, Robertson and Paterson 1982, Fincke et al. 2006). Also, males with experimentally altered cerci are rejected by conspecific females (Robertson and Paterson 1982). Thus, the morphologies of these male and female structures seem to be critical for mate recognition, and so the evolution of these structures may play a vital role in speciation in Enallagma. These structures are akin to a lock-and-key mechanism, with each sex potenitially evaluating the fit between the male's cerci with the contours of the female's mesothoracic plates."

http://www.enallagma.com/cerci/damselflyMating.html

Immature damselflies (known as naiads), live in the stream for a year or so until one emerges into the world of air and becomes the light-weight flying thing that resembles a dragonfly. The adult version will live for a few weeks to a few months, during which time its only real purpose is to mate. The articles above tell the first part of this story. The other part begins with the male arching his long abdomen over to his own abdomen where he will deposit sperm on the underside of about the second segment. (Some sources say that the male deposits his sperm onto this accessory sex organ before searching for a female.) He then clasps onto the female behind her head and she arches her abdomen under and around to retrieve the sperm. She, then, will lay her fertilized eggs on the surface of waters, bits of plant emerging from the water, in the mud, drilled into plant stems, or let go in the warm summer or autumn air itself .

Here's a drawing of part of the Act:

From the Pond, past the 3 1/2 pairs of damselflies, across the Stonefield,
and to the old Ruth Berry pressure pump.

And then up Whitman's Rough.

I focused mainly on the cedar elms along the east slope of Whitman's Rough above the home site. Buckeyes, junipers, persimmons, and other trees are dying, too. While I was sitting in a thin patch of shade beside the hose, a three-inch long lizard appeared on a water-spattered boulder. He went from one wet spot to the next, "lapping" up moisture as if in a frenzy. I don't know where he and other animals could possibly be getting enough water to survive.

With no creek flowing into it, the Pool warms and evaporates,
shrinking the universe for dozens of fish, tens of thousands of insects,
and gazillions of smaller invertebrates.

Oasis

Blotched Water Snake

(Nerodia erythrogaster transversa)

This particular snake was filmed swimming in the north end of The Pool. After watching it for a few minutes, I went around to the other end of the pool, sat on a broad stone, and spent the next hour watching four such blotched water snakes swim around the pool's edges and back and forth across the small waters. Once, a Nerodia swam to the center of the pool and floated still. Then another swam out to it and immediately the two of them splashed the water about and then swam off in different directions.

I should admit that the species named here may or may not fit the actual snake seen here. The genus is right on, but Nerodia includes a number of snakes. They all live a semi-aquatic life, though, and all of them can be aggressive (an evolutionary piece of mimicry from living near poisonous cottonmouths?). Fish, amphibians, and rodents are not safe around Nerodia.

Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Colubridae
Subfamily:	Natricinae
Genus:	Nerodia

For more information on snakes and reptiles of our area: http://www.austinreptileservice.net.

Exuvia of a dragonfly.

The exuvia is the remains of the insect's exoskeleton.

For more information on dragonflies and damselflies, here's a nice site: http://odonatacentral.org.

Red-eared Turtle (Trachemys scripta)

Notice the strong "keel" on the carapace of this young specimen. As it ages, the ridge on its back will weaken out more. This one was resting quietly on the edge of the very small stream emerging from stones about eighty feet south of the lower end of The Pond. I saw no others nearby.