JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from the valley of the Dry Frio River on the
southern slope of the Edwards Plateau, northern
Uvalde County, southwestern Texas, USA

March 3, 2013

STRUTTING TURKEYS
Spring is in the air, a whole new season of baby-making is on hand for many creatures, and often on mornings when I jog in the predawn darkness it's with the accompaniment of Wild Turkeys calling from their tree roosts along the little Dry Frio River. They're not gobbling but rather making different sounds, sounds conveying a sense of excitement there among the trees, and you wonder just what is going on and what's on their minds.

Later in the morning after the sun comes up flocks of thirty to fifty or more turkeys can be found foraging along roads, in fields and even people's front yards. In this community they're not as wild as out in the ranchlands, but they still don't like for people to come too close, so when they see you coming they run away on their long legs, somehow ganglingly reminiscent of little feathered dinosaurs, which the fossil evidence and genetic sequencing tells us that all birds more or less are.

Typically in a flock of fifty or so they'll all be keeping in a loose flock, each bird busily foraging in the grass for seeds, grasshoppers, whatever, but at the edge of the flock and a little apart there will be two or three tom turkeys keeping close together, often fanning out their tail feathers, holding their wings out and fluffing their feathers, making themselves look larger, and the featherless skin on their heads and necks is very bright blue and red, all shown in the picture at http://www.backyardnature.net/n/13/130303tu.jpg.

The rest of the flock consists of rather slender, skittery females and "poults," a poult being an immature turkey, pheasant or similar kind of bird. Nowadays the few "toms," or males, strutting so splendiferously at the flock's edge are transformed by increasing daylight hours, which stimulate their sex hormones. As days become still longer and warmer, the hen population will fragment into small flocks and disperse widely to good nesting spots. Soon the strutting fraternity of toms will split up, too, each bird following hens around in the woods, gobbling lustily, trying to attract as many to his harem as possible.

On each puffed-out chest of these lumbering, strutting toms there's a conspicuous "beard," as you can see at http://www.backyardnature.net/n/13/130303tt.jpg.

The beard's stiff, featherlike “hairs” are called “bristles” or “mesofiloplumes.” The beard grows slowly, year after year, and can reach a foot long. Therefore, the longer a tom's beard, the older he is, and from the typical hen's perspective that's a desirable trait. Females prefer toms with long beards. It makes sense, evolutionarily, because a tom with a long beard is clearly one smart enough and powerful enough to survive to a long-bearded age, and therefore is more worthy to pass his genes along to the next generation.

*****

A WHITE BLACK VULTURE
Speaking of spectacular birds, my neighbor Fred sent me a picture he took over a year ago four or five miles south of here near Reagan Wells, in the valley of the Dry Frio River. It shows a bird unlike any he'd ever seen, and hasn't seen since. It's shown at http://www.backyardnature.net/n/13/130303vu.jpg.

That's a Black Vulture. The question arises as to whether he's an albino or a "leucistic" individual, the difference being that albino organisms are white or whitish because they lack the black pigment melanin, but still may produce pigments such as orangish carotenoids, while leucistic organisms lack all pigments. Albinos, therefore, often look yellowish or display some other light coloring, while leucistic birds are absolutely white. But, if a bird is naturally totally black, how do you know whether it's white because of lack of melanin, or because all pigments are missing?

Our white Black Vulture has pink eyes and pinkish skin, but that's blood coloring, not skin or feather pigment. Our bird's tail feathers are lightly stained but that may be from pooping.

Cornell University has a web page explaining the differences between albino and leucistic birds. There they say that "Solid white birds with pink eyes everyone agrees are albinistic, and pale birds with normally colored but pale plumage everyone agrees are leucistic."

Therefore, our white, pink-eyed bird must be an albino. And my neighbor Fred took an amazing picture, one that vindicates his practice of paying attention as he moves around, and carrying a camera with him wherever he goes.

*****

TEXAS PINE SILVERFISH
On a nearby rocky hillside my picking up a rock caused a half-inch long (11mm), slender, six-legged, stiff-bodied critter to skitter across the ground. You can see him at http://www.backyardnature.net/n/13/130303sv.jpg.

A fine view of the head showing the body heavily mantled with scales is at http://www.backyardnature.net/n/13/130303sw.jpg.

The arthropod was conspicuously segmented and grayish like a centipede but with six legs he had to be an insect, and centipedes with their many legs aren't insects. He was shaped like a silverfish but I think of silverfish as whitish and more soft-bodied than this one looked. Still, volunteer identifier Bea in Ontario was convinced it was a member of the Silverfish Family, the Lepismatidae, a family holding about 190 species of primitive, wingless insects. Therefore I was tickled to find on the Internet a freely available 1972 paper entitled A Review of the Silverfish of the United States and the Caribbean Area at http://digitallibrary.amnh.org/dspace/handle/2246/2689.

That paper led me to the name: ALLACROTELSA SPINULATA, sometimes known as the Texas Pine Silverfish, despite the fact that it occurs far beyond Texas -- throughout most of the western US and into Mexico. However, judging from the lack of pictures and information about the species on the Internet, it must be rarely noticed, maybe because normally it occurs beneath objects on the ground and under tree bark. You just have to blunder upon one, as I did.

So, this was a good find, a reminder that all silverfish aren't like the pale, flexible-bodied critters we see in basements and libraries with old books. The silverfish we normally see in our homes -- the Common Silverfish, Lepisma saccharina, and the Firebrat, Thermobia domestica -- are invasive species, but the Texas Pine Silverfish is a native species who politely stays in the woods not bothering humans at all. They are omnivorous scavengers, well-mannered little garbage collectors who unobtrusively work out of sight and out of mind.

And when we see them, taking into account their primitive roots, we can think of their winglessness as a feature of a time so long ago that insects hadn't yet settled on the notion that wings might be a good idea.

*****

APHID MUMMIES
During January's chilly days our pot of Calendulas became infested with aphids and the plants began looking droopy and anemic. But now that spring with warmer and longer days is arriving the Calendulas are perking up and the aphid population has diminished dramatically. I'd thought that maybe with more warmth and sunlight the Calendulas' immune system may have kicked in causing the aphids' decline, but after taking a closer look, I'm suspecting something else may be behind it.

First, at http://www.backyardnature.net/n/13/130303am.jpg you see a typical patch of Calendula leaf undersurface occupied with aphids. In the picture there's only one living aphid, the dark one at the image's bottom center. The white, papery items are exoskeletons shed by growing aphids. The four spherical, tan-colored forms are aphid mummies, and in that, there's a story. A close-up of two mummies hints at the story at http://www.backyardnature.net/n/13/130303aq.jpg.

One mummy's rear end has a circular hole in it and the other mummy's rear end has a hole with the lid still on it.

The story begins when a tiny wasp inserts an egg into the aphid. In about two days a wasp grub hatches and feeds on the living aphid by osmosis for about six to eight days, killing the aphid. During this time the larva expands in size so that the aphid's body swells, giving it a bloated appearance. The larva cuts a slit in the bottom of the aphid, and, working from inside the aphid, attaches the dead aphid to the leaf with silk and glue. Then the wasp grub still inside the mummy molts to the pupal stage as the dead aphid turns from green to brown, becoming a "mummy." After four or five days a wasp emerges from the pupa inside the mummy and exists the aphid by cutting a circular hole in the mummy's top. If you don't believe that, I actually observed a black wasp emerging from a mummy's rear end, shown at http://www.backyardnature.net/n/13/130303ap.jpg.

Wasp parasitization not only controls aphid populations by killing individual aphids, but also by reducing the living parasitized aphid's reproductive rate. Parasitized aphids stop reproducing within one to five days, while healthy aphids give birth to three or four live aphids each day for 25-30 days.

The control of aphids by introducing parasitic wasps into infested areas is an established procedure in the field of biological control. One website sells 500 wasps for US$43.00, or 10,000 wasps for $340. The wasps, whose name is Aphidius colemani, are shipped as parasitized aphid mummies from which adult wasps will emerge and theoretically parasitize many more than just one aphid. For control of aphids on an acre of land, it's suggested that 500-3,000 wasps be released two or three times, one week apart, depending on the extent of infestation.

*****

A MICROSCOPIC FRESHWATER WORM
At http://www.backyardnature.net/n/13/130303wm.jpg you see what turned up during this week's microscopic safari into a drop of water from an inch-deep (3cm) riffle in the little Dry Frio River behind the cabin. This wormy creature was much larger than most critters we've been identifying in the Dry Frio's waters, about 1mm long (1/32nd inch), but still small enough not to be noticed unless he's on a slide with good lighting.

In the above picture notice at the picture's lower, right corner the open mouth funneling into a narrow esophagus leading to the dark, well filled stomach and intestines. Also note along the animal's lower surface the presence of short, needle-thin bristles, or setae, which appear to be serving as legs as the creature maneuvers through his jungle of filamentous algae. These setae provide an important clue as to the being's identity.

For, it's what we sometimes call a "bristle worm," a name applied to a class of segmented worms that in biology class students learn to call "polychaetes," the Class Polychaete. Polychaetes are annelids, so our aquatic, microscopic little worm is a member of the same phylum as the earthworm, the Phylum Annelida.

In general, polychaetes are thought of as typically marine, with each body segment bearing fleshy, leglike protrusions called parapodia, from which the bristles or setae arise. Therefore, our bristle worm from the Dry Frio is a little unusual for the class, since it lives in freshwater and its parapodia aren't very noticeable unless you look for them. Of the 10,000 or so polychaete species known to science, Only 168 species -- less than 2% of all polychaetes -- dwell in freshwater.

Our tiny polychaete seems to belong to the genus AEOLOSOMA, a genus whose members specialize in freshwater habitats. Several species of Aeolosoma are known, but I can't say which we have. It seems to be fairly common in the Dry Frio's shallow spots where running water passes over mossy limestone cobbles.

*****

CREEPING WOODSORREL FLOWERING
Though a few hundred feet lower in elevation just south of us spring is well advanced with green lawns, leafed-out trees and irises flowering, here along the Dry Frio River partway up the Edwards Plateau it's hard to find newly flowering plants. However, at the base of the sunny side of the cabin this week a certain little yellow-flowered and very welcome weed was good enough to blossom, as you can see at http://www.backyardnature.net/n/13/130303ox.jpg.

A close-up of the hairy, clover-like leaves is shown at http://www.backyardnature.net/n/13/130303oz.jpg.

Anyone familiar with his or her local wildflowers knows that a herbaceous plant bearing trifoliate, clover-like leaves but regular, un-clover-like flowers that usually are yellow or pink, is one of the woodsorrels, genus Oxalis. As a group, woodsorrels are among the easiest to recognize wildflowers, but figuring out which woodsorrel you have can be a challenge, for about 800 species are recognized. The easiest way to confirm that you have a woodsorrel is to nibble a leaf, because woodsorrel leaves are very acidic. Sometimes woodsorrels are called sourgrasses, though of course they have nothing to do with the Grass Family.

At http://www.backyardnature.net/n/13/130303oy.jpg you see features of the Oxalis flower making it an Oxalis: Five sepals and five petals, but ten stamens, five of the stamens with long filaments, five with short ones, and the stamens are joined at their filament bases into a cylinder surrounding the female pistil. Atop the pistil are five styles.

The species in the picture, OXALIS CORNICULATA, is often called Creeping Woodsorrel because its shoots tend to sprawl or creep across the ground, often rooting at the nodes. The species is so commonly found throughout the world that it's hard to say where it originated, though it's not regarded as North American.

Some literature says that Creeping Woodsorrel's leaves are tinged with reddish purple, but our plant is entirely green, and it's known that sometimes the species' leaves display no purplish at all.

In North America we have another widely distributed, very common, weedy woodsorrel species looking more or less like our Creeping Woodsorrel -- it's the Common or Yellow-flowered Woodsorrel, Oxalis stricta, a native species -- so it's good to know the secret that easily distinguishes them. You can see the secret proof that our cabin-side plant is the Creeping Woodsorrel at http://www.backyardnature.net/n/13/130303ow.jpg.

That picture shows a part of the Creeping Woodsorrel's stem where several slender leaf petioles join the much thicker, vertical stem. Notice that at the base of each petiole there are rectangular flanges with hairs arising along their edges. These flanges are stipules, the main purpose of which usually is to protect emerging tissue until it's mature enough to withstand the elements. The nice thing is that the other very similar species, the Common Woodsorrel, doesn't have such stipules. It's a neat trick to know.

Woodsorrels are so acidy that you can pick whole plants, brew them in hot water, let the water chill, add sweetener, and you get a pretty nice drink.

*****

AN UNUSUAL ALGA
Lately an unusual and distinctive alga has been showing up in microscopically examined water from the little Dry Frio River behind the cabin. You can see what's so interesting about it at http://www.backyardnature.net/n/13/130303ag.jpg.

Unlike most of the algae we've looked at, this one is not filamentous -- not composed of elongate cells attached end to end. Here solitary, spherical algal cells, each cell containing one photosynthesizing chloroplast, are clustered into small, more or less geometrical groupings about 0.5mm across (1/64th inch) and evenly spaced from one another as if held in place by unseen forces. If you look closely you can see that the individual cells are embedded in what appears to be thick, transparent coverings of a jelly-like substance -- referred to as their "mucilaginous sheaths."

Not many algae species look like this, so it was easy to narrow our specimen's identity down quite a bit. The excellent, illustrated but not-yet-finished "web key" to algae genera at http://www.algalweb.net/search1.htm led me to the genus SPHAEROCYSTIS. The four or so species in that genus are described as freely floating -- or planktonic -- inhabitants of freshwater found in Europe, North America and South Africa. Other genera with very similar if not identical species are recognized, since the taxonomy of this group of algae is poorly understood.

Therefore "Sphaerocystis" is just an educated guess, the name we'll file our picture under on the Internet to let the world know that the species resides here in Uvalde County's Dry Frio River in southwestern Texas. I'll bet that some later student of the group one day will be tickled to see it.

*****

FEATURED ESSAYS FROM THE PAST:

"Three Perfect Poles," from the February 25, 2008 Newsletter, at http://www.backyardnature.net/n/p/080225.htm

"Three Ways to See Beauty," from the January 1, 2012 Newsletter, at http://www.backyardnature.net/n/p/120101.htm

*****

Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at http://www.backyardnature.net/n/.

Visit Jim's backyard nature site at http://www.backyardnature.net