February 16, 2014
BLACK FLY LARVAE AT A CULVERT
Even after so many months of drought, water flowed in a clear stream about half an inch deep (13mm) from a corrugated metal culvert where the road dipped into the little Dry Frio River at one of our famous "low-water crossings." A buttonbush shaded the trickling water and algae or cyanobacteria formed a spongy, green carpet over the culvert's outflow lip.
Up close, the greenish carpet was speckled with black, oblong items, like a submerged moss colony issuing black capsules. I'd never seen such a thing so I pinched some "black capsules" from the water, which you can see squirming on my fingertip at http://www.backyardnature.net/n/14/140216gb.jpg.
About 3/16ths inch long (5mm), they're aquatic insect larvae with curiously big bottoms! You can see them up close at http://www.backyardnature.net/n/14/140216gc.jpg.
What's missing in that picture is the animation, for though the flow was a mere trickle, in this tiny ecosystem the water's rippling surface sparkled and the black larvae oscillated back and forth almost violently, like small flags in a stiff breeze. Closer up still the individual larvae displayed not only big bottoms but also their segmented bodies and antenna-like appendages on their heads, shown at http://www.backyardnature.net/n/14/140216gd.jpg.
Later that day, on another project I stumbled upon a picture of exactly what's shown in our pictures. It was labeled "Aquatic Black Fly Larvae, Simulium species." Other pictures of aquatic black fly larvae also matched our pictures. A University of Florida webpage on black flies says that black fly larvae live only in well oxygenated, flowing water, and further remarks that "They will be particularly abundant near culverts under roads, attached to plants trailing in the water." Moreover, entomologists have collected black flies of the genus Simulium in Uvalde County.
So, our pictures show aquatic larvae of the black fly genus SIMULIUM, of which several hundred species are known. Knowing the genus, now we can look up what those antenna-like things are on the larvae's heads. It turns out that they're "cephalic fans" used for filtering food such as minute organisms and debris, which is snared by sticky material on the fans. Our pictures show that the fans can be withdrawn. I read that the larvae's mouthparts -- "mandibular brushes" and "labral bristles" -- comb what adheres to the fans into the mouth. The larvae of many black flies also are able to scrape the substrate they're attached to.
The University of Florida sees fit to offer a page on black flies because females of the species, needing protein for their eggs, take blood from a wide range of host species, including cattle, horses, sheep, goats, poultry, other livestock and wild mammals, birds, and humans, depending on the black fly species. And the bites can hurt, and sometimes transfer diseases. The flies cut into the skin, feed on the resulting pool of blood, and inject anticoagulants to keep the blood flowing. The anticoagulants can cause mild to severe allergic reactions in sensitive individuals, and the bites can itch for days. In large enough numbers, black flies can cause anemia in a host.
So, the adults can be disagreeable, but those larvae so busily filtering sparkling water flowing over their undulating green pasture creates such a pretty scene that you just can't help but wish them every success.
RED-SHOULDERED HAWK ON A POLE
In late afternoon I was lying in a large field of windblown King Ranch Bluestem when a broad-winged, short-tailed, buteo-type hawk came flying in a straight line low over the grass. He alighted on a nearby power pole, bent forward and began staring hard into the undulating grass below, searching for his usual prey of rodents, insects and small birds. You can see his stance at http://www.backyardnature.net/n/14/140216hk.jpg.
It was a Red-shouldered Hawk, and in the picture you can see that not only is his shoulder a dark, rusty color, but also his head and chest. And the chest is horizontally barred, not vertically as with some other species.
Red-shouldered Hawks are mostly an eastern species, so we're at its western limit of distribution, except for a disjunct population in California. In the northernmost part of its distribution the birds are migratory, but here they stay year round.
BARK BEETLES ON ASHE JUNIPER
Our forests here on the southern slope of the Edwards Plateau are dominated by two main native trees, the Texas Live Oak and the Ashe Juniper. In an earlier Newsletter we saw that our liveoaks are suffering from "Oak Decline," at the root of which is the severe stress brought on by our multi-year drought. The stress makes trees vulnerable to a wide range of disease organisms that in normal times wouldn't amount to much. Nowadays bark beetle holes are showing up in our second dominant tree species, the Ashe Juniper, two resin-oozing holes of which are shown at http://www.backyardnature.net/n/14/140216ju.jpg.
Normally a few bark beetles won't imperil a tree, but when trees are weakened by long-term droughts and other stresses, the beetles can attack en masse, ultimately killing the tree.
COMMON THELIA MOSS
It's so arid here that you don't see many mosses, but when you do it's something special needing a closer look. And the first thing you check for is whether they have capsules, for normally they're needed for a good identification.
The other day, however, a species came along that just from its general growth patter it was recognizable as a species I've seen a lot of in the East. With tough, vertically climbing stems issuing many upward-curving side stems, the plant formed a dense, coarse, yellowish green mat on a liveoak trunk leaning across an arroyo. It was a good place for absorbing humidity from wind streaming down the rarely flowing stream. You can see it at http://www.backyardnature.net/n/14/140216ms.jpg.
Though it was an extensive patch, it bore only a few capsules, and they were somewhat immature, but at least you could determine that they arose from the moss's stems and not from the stem tips as in many moss species. Capsules are shown at http://www.backyardnature.net/n/14/140216mt.jpg.
Having snipped off a branch, back home under the microscope the tiny leaves showed themselves as broad-based but coming to a slender, sharp tip, and with leaf margins bearing low teeth, as shown at http://www.backyardnature.net/n/14/140216mu.jpg.
Leaf cells were very distinctly thick-walled and diamond-shaped, as shown at http://www.backyardnature.net/n/14/140216mv.jpg.
Back East this well known moss is called the Common Thelia. It's THELIA HIRTELLA, in North America distributed from Nova Scotia to Kansas, and south through Florida and Texas into northeastern Mexico and the Dominican Republic. We're on the extreme western limit of distribution, which may explain why our moss's leaves aren't as hairy-margined as the literature says they usually are; individuals at distribution fringes often differ a little from those in the population's center.
An interesting word turning up in descriptions of the Common Thelia is "julaceous." It means "like an ament," or "bearing aments," an ament being a spike-like cluster of flowers without petals, with each flower associated with a scale. Ament scales normally are so close-packed and overlapping that the exposed tips of the aments give the stem a cylindrical and coarse look. Leaves on the Common Thelia are similarly close-packed and overlapping, creating tough, cylindrical stems.
On the hard Edwards Limestone of early Cretaceous age capping our hill, covering a hand-high vertical face beneath a little overhang facing eastward, a new lichen turned up, a foliose one looking like lots of little gray fingernails of various sizes all crammed together as shown at http://www.backyardnature.net/n/14/140216dm.jpg.
Something unusual about this lichen gave me hopes of being able to identify it, despite there being no cuplike, spore producing apothecia, which normally are needed for identification. The atypical feature was that the lichen's smooth thallus surfaces were dotted with tiny, brownish spots, as shown at http://www.backyardnature.net/n/14/140216dn.jpg.
Even the thalli's pale brown undersurfaces were speckled with dots, seen at http://www.backyardnature.net/n/14/140216do.jpg.
Since in the Northern Hemisphere this is a widespread species and in some places is fairly common, it was easy to find labeled pictures of it. It's DERMATOCARPON MINIATUM -- not so common as to have a common name -- and lichenologists already have collected it on limestone in Lost Maples State Natural Area in the neighboring county to the north of here. This is the first time I've noticed it in our canyon, though.
Experts refer to the conspicuous brown dots on the thallus surface as "ostioles of perithecia." Ostioles are small pores on the body's surface, and perithecia are spherical, cylindrical, or flask-shaped hollow fruiting bodies of certain fungi containing the microscopic, spore-producing structures known as "asci."
Our Dermatocarpon lichen didn't have the usual apothecia because the species doesn't produce them. It issues its spores from its ascus-coated ostioles instead. In fact, certain old literature refers to the ostioles of Dermatocarpon as apothecia, but I don't find that usage in modern works.
FIREDOT LICHEN #2
A jaggedly eroded, matchbox-size rock lying loose atop the Edwards Limestone capping our hill bore a tiny, yellow-orange smudge that needed looking at. Up close, the smudge turned out to be a very small lichen. You can see it, just below a similarly miniscule grayish lichen, and with the tip of one of my fingers nudging in from the right to show how very small all this lichen is, at http://www.backyardnature.net/n/14/140216fd.jpg.
Carrying the rock home to look at it below the dissecting scope, the orangish lichen displayed cuplike, spore-producing apothecia like most lichens, but only about half a millimeter across (±1/30th inch). You can see some at http://www.backyardnature.net/n/14/140216fe.jpg.
We've encountered a similarly structured but larger lichen on limestone, one with bright, reddish-orange apothecia, not far from here, the "Firedot" shown at http://www.backyardnature.net/n/x/firedot.htm.
Our hilltop lichen also was a firedot, meaning that it was a member of the genus Caloplaca. Depending on your expert, about 88 Caloplaca species are listed for North America. There's even a Caloplaca obamae named for President Obama, discovered in 2007 in California. The best I can tell, this one is CALOPLACA SUBSOLUTA, which occurs worldwide and is found only on rocks, both limestone and other kinds.
In Biology 100 we learn that lichens come in three types: crustose, foliose and fruticose. This Firedot doesn't fit neatly any of those categories. The LichenPortal.Org website describes it as "squamulose, areolate or subsquamulose." Squamulose refers to scales, and areolate means having its parts separated by small spaces -- a cracked appearance.
NITELLA WITH OOGONIA
In December we looked at a large, pretty alga in the Dry Frio known as Nitella. You can review what Nitella looks like at http://www.backyardnature.net/n/x/nitella.htm.
Algae don't produce flowers, fruits and seeds, but nowadays our Nitella is loaded with reproductive structures that any honest student might look at and call fruits or seeds. At least call them that if seen under a dissecting scope, for they are so small that otherwise they're hardly visible. You can see how crowded they are among Nitella's branches at http://www.backyardnature.net/n/14/140216oo.jpg.
The dark, spherical items are the fruitlike things. In daylight they are tan colored and the Nitella stems are green. They are antheridia, which contain sperm, so they're analagous to male flowers on flowering plants. On Nitella, antheridia are more or less spherical and ornamented with various patterns that vary from species to species, and so are very important in identifying Nitella to species level. The female parts, called oogonia, contain eggs, are a little larger and are crowned with noticible rings of cells.
The species of our Nitella remains unknown, so in the hope that later someone can identify our species, I overexposed an antheridium to show its ornamentation, which is shown at http://www.backyardnature.net/n/14/140216op.jpg.
NOSTOC UNDER THE MICROSCOPE
Last winter we looked at the strange, gelatinous, irregular ribbons of greenish-to-brownish "Witch's Butter" that emerges from our ground here and there. Witch's Butter is a remarkable and ecologically important cyanobacterium of the genus Nostoc. You can see it emerging from the soil on our Nostoc page at http://www.backyardnature.net/n/x/nostoc.htm.
Textbooks often show Nostoc cells, which look like long, twisting strands of beads that don't look the least like our Witch's Butter. I've never reconciled the appearance of Witch's Butter with those snaky filaments, so this week when I found some littering very thin soil atop our limestone hill I took a sample and back at Juniper House looked at a thin sheet of it beneath the microscope. At lower magnifications all I saw was brown, jelly-like stuff, but finally at the highest power I saw what's shown at http://www.backyardnature.net/n/14/140216no.jpg.
So, the gelatinous material we call Witch's Butter is mostly mucilage in which long, curving filaments of connected cells are embedded. I read that Nostoc colonies take on a variety of macroscopic appearances, depending on the species, including for that are smooth or warty in texture, loose or dense, spherical, flat, gelatinous, or in irregular mats.
More information about Nostoc is available on our Nostoc page linked to above.
A BEAKFUL OF FEATHERS
During the couple of months the birdfeeder has been up maybe 95% of my visitors have been Black-crested Titmice and Chipping Sparrows, with the sparrows forming a slight majority. You think of titmice as tiny, cute birds, but they're larger than the sparrows and likely to dominate in a confrontation over feeding rights; they loom over the sparrows like centurions in black-plumed helmets. Watching through the window, I've grown to think of Chipping Sparrows as peaceful and timid.
A couple of weeks ago, however, among the sparrows little spats involving pecking began breaking out over who might have this or that seed. Before long real conflicts arose between pairs who suddenly couldn't endure one another's presence. Sometimes they'd fly at one another, rising into the air as if both were climbing an invisible ladder between them, showering one another with pecks and wing flaps. Finally this week one went berserk when another landed on his side of the feeder, stabbed his beak into the interloper's chest, and plucked out a large tuft of feathers, while other feathers drifted to the ground. It was a savage attack that a month ago would have been impossible to imagine.
But, of course, spring is coming. Hormones are flowing. It's long been known that as days grow longer -- as the photoperiod increases -- the sexual organs swell, secrete more hormones, and birds just can't avoid undergoing many kinds of behavioral changes. Nowadays Cardinals and Bewick's Wrens have begun singing and fights are even breaking out among Mourning Doves gleaning seeds below the feeder. Throughout the night Axis Deer whistle-snort, and all across the early morning, moonlit landscape flocks of Wild Turkeys erupt in gobbling. And you've seen the emerging insect larvae we've documented. These longer days are causing a revolution in the whole natural world here.
So, none of this big change in behavior is a mystery, but, still, the feeder fighting raises an interesting question. That is, what does it say about the Creator's manner of being that She's designed things so that a bird's spring courtship period must involve such pecking, hurt feelings and outright pain as is on display every day at the feeder? Why couldn't the surge of hormones simply dispose the birds to drift away from their wintertime communities, establish territories and acquire mates, simply forgoing all that rage, pecking and feather plucking?
Actually, philosophers and behavioralists have looked at that question for a long time. In general, the deal is that aggression is adaptive, because those who get away with it on the average end up getting more food, claiming the best homes, getting the sexiest partners, producing the most offspring, and in the long run creating a more dynamic and successful species. Greed, jealousy and general cantankerousness in a given season are tools the genes employ to fine tune the species.
So, I've come to accept that it's OK for my sparrows to be ornery with one another, at least when the photoperiod is increasing. There's not much a sparrow can do about it, anyway.
But, that still doesn't answer the question of what it means that things are organized this feather-pulling way to begin with. Nor does it address the matter of whether we humans, with our big brains and our ability to countermand many of the dictates of our genes, might learn to handle certain of our own urges a bit more elegantly and causing less pain than the sparrows.
FEATURED ESSAYS FROM THE PAST:
"Iguana Fights, Money & Enlightenment" from the March 18, 2006 Newsletter, at http://www.backyardnature.net/n/p/060318.htm
"Toad-Squashing Morality" from the September 7 2007 Newsletter, at http://www.backyardnature.net/n/p/070907.htm
Best wishes to all Newsletter readers,
All previous Newsletters are archived at http://www.backyardnature.net/n/.