January 26, 2014
DARK-WINGED FUNGUS GNAT
Several goldfish bowls stand on one of Juniper House's windowsills filled with water, mud, pebbles, decaying leaves and interesting blobs of algae and cyanobacteria from the little Dry Frio. When morning's sunlight slants through the window, the bowls' waters are thick with bright specks of microscopic critters swimming about. New things turn up constantly, snails hatching, planaria wandering across leaves, tiny aquatic insect larvae pulling themselves onto emerging vegetation, molting and flying away. Every day each bowl has new stories to tell.
The other day a tiny winged insect only about 1mm long (1/32 inch) -- what most people would call a gnat -- turned up in one of the bowls floating dead on its side at the water's surface. I didn't know what the gnat was doing there, but it seemed that here was a good chance to learn more about gnats. The little being was fished from the water, placed beneath the dissection scope, and you can see the resulting image at http://www.backyardnature.net/n/14/140126gn.jpg.
What encouraged the hope that this gnat might be identifiable was the way it lay on its side so clearly displaying the veins in a wing. In the world of insect identification, wing venation is like fingerprints for human identification. Surfaces between veins form "cells," and cell configuration is constant from species to species.
Mostly on the basis of wing venation, volunteer identifier Bea in Ontario figured out that we had a member of the insect family known as the Sciaridae, members of which often are called dark-winged fungus gnats, which commonly are found in moist environments. About 1700 species of dark-winged fungus gnats are known, but it's estimated that about 20,000 are awaiting discovery, mainly in the tropics. Among features making good field marks for recognizing dark-winged fungus gnats are the long legs, the long, slender abdomen, and the threadlike antennae consisting of several segments.
In the picture you might notice that behind the extended wing there's a small spoon-shaped object. That's a modified back wing known as a halter or haltere. Halteres function as gyroscopes, helping keep the insect's body from rotating during flight. Since halteres are modified back wings, they occur only on insects with one pair of wings. In fact, gnats belong to the Fly Order, the Diptera, containing species with only one pair of wings.
Though we don't hear much about "dark-winged fungus gnats," if we spend even a little time outdoors we're bound to have noticed them. Studies show that in many moist and shadowy areas, up to 70% of all two-winged species encountered can be members of this family, the Sciaridae. Though adult gnats flitting around eyes and ears can be a bother, we can be grateful to the larvae of many species for performing the important role of turning leaf litter into soil.
By no means are all gnats dark-winged fungus gnats. The word gnat is a general term applied to many different kinds of tiny fly-like or two-winged insects. About as technical as you can get in saying what a gnat is, is that it's a tiny flying insect in the Dipterid suborder Nematocera, especially in the families Mycetophilidae, Anisopodidae and Sciaridae. To confuse matters more, in British English even certain blood-sucking mosquitoes are called gnats.
Also in our goldfish bowls containing water, muck and debris from the Dry Frio, the most eye-catching occupant is a tiny animal only about 1mm long (1/16th inch). Though so small, it's conspicuous because of its bright red color. In the Dry Frio's shallow, clear waters you almost always spot one or more of these red specks swimming through the water (not atop it). The bottom side of one crawling up a fishbowl's inner surface is shown at http://www.backyardnature.net/n/14/140126mi.jpg.
In that picture, notice the long hairs, or setae, on the hind leg, helpful in swimming. A view of the same individual below a dissecting scope, showing eye spots, and dark spots inside the body that possibly are eggs, is at http://www.backyardnature.net/n/14/140126mj.jpg.
The inset in that image's upper, left corner shows the mouthparts from below, mouthparts that look more useful for piercing and sucking than for chewing.
This is a water mite, which technically can be referred to as a Hydracarina. The term Hydracarina doesn't apply to a species or even a genus; it's a general term for many families of water mites. About 5000 Hydracarina species are known, but it's assumed that many, many more are to be discovered, since they've been little studied in the tropics. Water mites are not insects of the class Insecta (with six legs), but rather are arachnids, like spiders, of the class Arachnida (with eight legs).
Nearly all water mites occur in freshwater habitats, not marine ones. Most species are carnivorous, seizing upon worms, small crustaceans and small insects, piercing the cuticle of their prey with their mouthparts, then sucking out the juices. Our individual is about normal in size, the smallest species being about half as large (0.5mm) while the largest reach 8mm (5/16ths inch). Like ours, many species are vividly colored, besides red also being yellow and orange. Apparently the bright colors warn fish of the mite's unpalatableness, which probably is due to noxious secretions from their skin glands.
The larval stage of many water mite species is parasitic, often on or inside winged insects, which transport the larvae far from home. I don't know whether our Dry Frio species has a parasitic larval stage or not.
Whatever the secret details of their life history, our brilliantly red water mites are a striking feature of the Dry Frio's shallow, clear water, if you but take the time to sit along the banks awhile, gazing into the water.
To discover uncommon plants, one approach is to seek out uncommon habitats. Along the little Dry Frio River, one such habitat is where water emerges from the base of gravel bars blocking the river's flow. Flowing water disappears into the gravel upstream, then issues from it downstream. It was in mud beside a spot where water trickled from the gravel that the flowering plant turned up shown at http://www.backyardnature.net/n/14/140126cc.jpg.
Finding this plant flowering here surprised me. It's not one of those perennial wildflowers or mixed-up invasive weeds that might turn up flowering anytime during the year after a week or two or warmness, or a good rain, but rather a spring-flowering annual herb. The little herb really figured that it was springy enough to flower! A close-up of a spray of its tiny flowers can be seen at http://www.backyardnature.net/n/14/140126ce.jpg.
Each flower's five petals is white tinged with pink, and only about 0.3mm long (1/100th inch). Notice how the petals arise atop the ovary, or future fruit, making these flowers part of that minority of blossoms with "inferior ovaries." Also, notice that the flowers are arrayed in "umbels" -- more-or-less flat-topped flower clusters with all the flowers' stems, or pedicels, arising from one point. Moreover, several umbels unite to form yet a larger umbel, a "compound umbel." Whenever you see a flower cluster with this structure, the best bet is that you're dealing with what used to be called the Umbelliferae, but now is named the Apiaceae, and know commonly as the Parsley Family.
Other important field marks for identification are shown at http://www.backyardnature.net/n/14/140126cd.jpg.
First, the umbels arise on the stem opposite the leaves, and not at stem ends as with many members of this family. Second, the leaves are twice-divided, or bipinnate, and leaf parts consist of threadlike lobes. Leaves of plants in this family often are divided into tiny leaflets or threadlike sections, but this plant carries the concept to an extreme.
With such distinctive field marks this early blooming little herb was easily identifiable as Marsh Parsley, also called Fine-leaved Celery, Slender Celery, Slim-lobe Celery and other names. It's CYCLOSPERMUM LEPTOPHYLLUM, and unlike the rare native wildflower I was hoping for, it occurs worldwide in warm to tropical zones, and is considered a noxious weed in many areas. It arises from a taproot and despite our young plant's small size, it can reach knee high in height. Native to South America, in the US it's found coast-to-coast in the southern states. It thrives along streams, roadsides and in wastelands.
Why is our Marsh Parsley flowering so early? Probably water issuing from the gravel bar has been warmed by the gravel. Also, the plant grew on a south-facing slope, and our recent weather has bee unusually warm and sunny.
Despite the "celery" part of some of its common names, it's not too closely related to Celery, though it's in the same family. Its leaves taste enough like parsley to be sprinkled in salads to add a little taste. I wouldn't use much, however, since the plant really isn't known as desirable for eating.
Some invasive weeds have bad reputations and almost universally are disliked, like crabgrass. Most don't draw attention to themselves and people have no opinions about them at all. A few are welcome immigrants. To me, Henbit has always been one of the latter, and this week one turned up in a corner of a raised bed of mustard greens, uninvited and overlooked until now, leaning against the south-facing wall of the bed. It benefited so greatly from the wall's daily reflected sunlight and nightly-reradiated solar energy that it was flowering, as shown at http://www.backyardnature.net/n/14/140126hb.jpg.
The plant's 5/8ths-inch long (15mm), purplish, bilaterally symmetrical corollas with their lower lips forming three-lobed landing pads for pollinators, the pads ornamented to draw attention, are shown at http://www.backyardnature.net/n/14/140126hc.jpg.
We've had a Henbit before, its page being at http://www.backyardnature.net/n/h/henbit.htm.
Still, just because it's such a welcome appearance, its flowering deserves special mention. Last year it didn't bloom here until March.
In the Texas Hill Country there's Oak Wilt and Oak Decline, two different things, and both are devastating our oaks. In our more arid southwestern corner of the region, we have Oak Decline but, so far, I don't see Oak Wilt. Oak Wilt is bad just to our east, for example in San Antonio, where it's killing many old street and park trees.
In our hilly area the forest is dominated by Ashe Junipers and Texas Live Oaks, with just a handful of other species sprinkled among them, especially Texas Red Oaks, which also are suffering from Oak Decline. Oaks are so dominant in our forests that if they disappear the very nature of our woodland ecology will be altered catastrophically.
You can see what Oak Decline looks like on trees beside Juniper House at http://www.backyardnature.net/n/14/140126ok.jpg.
Those are the tops of Texas Liveoaks, Quercus fusiformis, which are about 20 feet tall (6m). At this season healthy trees still bear their leaves; the leaves will fall in April as new ones emerge. The thing to notice is that major branches in the trees' crowns are leafless -- dead, in fact. They were dead this summer, and as time passes more limbs die in the trees' upper part. That's the main symptom of Oak Decline: Some branches dying while others don't, but the trend is toward all of them dying. Curiously, many oaks succumbing to Oak Decline also show what's seen at http://www.backyardnature.net/n/14/140126ol.jpg.
Those are new sprouts developing on the lower trunk of one of the trees shown above. As larger branches die above, new sprouts issue from the trunk close to the ground. Eventually even these will die, however. The amount of time taken for a tree to die completely depends on how much stress the tree is under, especially whether it's getting enough rain.
There's a disease organism involved, a fungus called Acremonium diospyri. However, this fungus is described as a "weak vascular pathogen," which means that it not very aggressively enters a tree's vascular system and clogs it so that water and nutrients can't get to where they're needed. The fungus becomes a serious problem only on trees already stressed, as our trees are by the drought experienced here during recent years. The disease caused by Acremonium diospyri is like measles among humans: Among healthy individuals it might be bothersome, but not deadly. Besides our Texas Live Oaks, other trees affected by Acremonium diospyri are Texas Red Oak, Post Oak, Water Oak, Willow Oak, Sycamore, Persimmon, Winged Elm, Hackberry, American Elm and Western Soapberry.
Every liveoak on our hill shows signs of Oak Decline, but those growing along the Dry Frio River are in good shape, apparently because they're getting adequate water. There's some indication that the fungus can be spread between trees by bark beetles. Confirming the presence of the fungus is hard, even for experts, so I'm only guessing that it's contributing to Oak Decline here.
Texas A&M University's Plant Disease Handbook suggests these steps for reducing die-back of liveoaks from Oak Decline: 1) Identify the problem; 2) Reduce stress on the trees; 3) Provide plenty of fertilizer and water; 4) Remove dead limbs on tree; 5) Don't import wood from areas with Oak Decline, and; 6)Plant trees other than those vulnerable to the Oak Decline fungus.
In our area of severe ongoing drought, on one hill among many with thousands of declining liveoaks, all we can do is to watch the decline take place, and hope for rain.
Each morning a little before dawn I run for half an hour along the little dead-end road in the valley. When I return the sky still is dark, but by the time I fix breakfast, tune in Public Radio's morning program and sit facing the wall-size window toward the east -- at about 6:30 -- the eastern horizon is turning pale, maybe with some color, silhouetting the trees outside my window and the hills across the valley. And, these days, there's a morning star, which you can see through my window at http://www.backyardnature.net/n/14/140126vs.jpg.
There's not always a morning star. This one just began appearing at my special time about a week ago. Each morning as light comes on, it stands a little higher in the sky, and eventually it'll drift elsewhere. This one will be our morning star for most of 2014, however. It'll be at its brightest on the morning of February 11, displaying a magnitude of -4.6. It's at -4.5 now, on January 26, so it'll grow yet a little brighter during the next few mornings. Remember that with regard to the magnitude of bright objects in the sky, the brighter something is, the lower its number of magnitude.
Of course, our morning star isn't a star at all, but rather Venus, second planet from the Sun.
Actually, this Sunday morning, January 26, Venus isn't the only astronomical entity orbiting the sun and occupying that patch of sky. A tiny bit south of Venus, if it were a bit brighter and the quarter Moon weren't bleaching the sky so, you might make out Pluto, glowing dimly with a magnitude of only 14.2. I was taught that Pluto was our Solar System's outermost planet, but in 2006 it was demoted from planet status to being only one of several large, icy bodies occupying the outer Solar System.
Unlike the large, bright planets of Jupiter and Saturn, you'll never see Venus on the opposite side of the sky from the Sun. Venus always remains near the Sun, whether as a morning star rising just before the Sun, or the evening star setting soon after the Sun, because Venus follows an orbit entirely within the Earth's larger orbit. In our morning sky, Venus will reach its maximum distance from the Sun in late March, then begin appearing nearer it each morning. Diagrams nicely showing how all this works can be studied at http://jeffreylhunt.wordpress.com/2013/11/27/venus-as-a-morning-star-2014/.
Having so few plants flowering nowadays I headed to a certain stretch of the little Dry Frio River where bare limestone exposed to full sunlight, and humidity from the nearby river, combine to provide a good place for lichens. Soon an interesting, new-to-me species turned up, the one at http://www.backyardnature.net/n/14/140126ps.jpg.
Forming a small patch on a horizontal bed of limestone, this lichen was of the foliose type -- leaflike. However, instead of its leafy body, or thallus, forming a ribbon inching across the rock and maybe forking here and there, the way so many foliose lichens do, its bodies were like brown, white-fringed fingernails stuck on the rocks. And the thalli were small, only about 4mm wide (7/32nds inch). Moreover, most thalli bore even smaller, even darker brown, disk-like growths atop them, which show up better at http://www.backyardnature.net/n/14/140126pt.jpg.
Lichens often bear on their upper surfaces cuplike growths known as apothecia, in which fungal spores are produced for reproduction. But these apothecia are not at all concave and don't have a rim the way the vast majority of others do.
With such distinctive color scheme, the small size, and the curious apothecia, this lichen was fairly easy to identify. It's PSORA PSEUDORUSSELLII, known at least by the USDA as the False Russell's Fishscale Lichen. Our lichen is "false" because it's similar to and closely related to Psora russellii, known as Russell's Fishscale, and because that lichen's binomial honors Russell, that's the "true" one.
Our False Russell's Fishscale is distributed mostly in southeastern North America but it extends west to Arizona, then south into arid northern Mexico, plus it turns up in Mediterranean Europe. Its habitat is described as "calciferous rock in open habitats," and of course limestone is the classic calciferous rock.
Several fishscale lichen species, genus Psora, are known, all displaying slight variations on the fingernail-like "theme" to which our False Russell's has introduced us. You might enjoy browsing "variations on the False Russells theme" at http://lichens.digitalmycology.com/macrolichens/Psora.html.
WHAT LICHENS TEACH
Nowadays with so few plants flowering it's worth paying special attention to lichens. Continually I'm surprised by lichen beauty and diversity, but maybe the most striking feature about them is something that's not immediately obvious: They're "composite organisms" consisting of two or three completely different species mingled together to form the single lichen species. It's like mixing a chicken with a dog to get a new, independent organism.
Every lichen is partly fungal. The fungus gives the lichen its form, helps it retain water and provides sexual reproduction of spores dispersed by wind and rain. Fungi don't photosynthesize, however, so a lichen's life cycle begins when the hypha from a lichen's fungus-produced spore finds cells of certain species of alga and/or cyanobacterium to wrap around or even penetrate, in order to take carbohydrates produced during photosynthesis. You could say that the fungus "parasitizes" the photosynthesizing species, except that the alga and/or cyanobacterium also benefit from the arrangement, so it's a close "symbiotic" relationship. The individual fungal, algal and/or cyanobacterial species constituting lichens often survive independently in Nature, but some species are known only as constituents of lichens.
Since the lichen-making partnership is so advantageous to everyone involved, it's easy to imagine how over time the original free-living species forming lichens could have evolved predispositions for entering the relationship,. However, why didn't evolution stop there, with lichen bodies never becoming more complex than simple crusts, like dried gravy smeared on rocks or tree stems? Once a fungus and its photosynthesizing partners have what they need in the relationship, what's the point in becoming more complex, more interesting, and more beautiful?
Lately we've seen that lichens go far beyond looking like dried, smeared-on gravy. We've seen the Sunburst Lichen's golden, leafy thalli branching and rebranching as they elegantly dispersed across twig bark; the Firedot Lichen's orangish fruiting bodies spectacularly ornamenting a white, crusty body; the Cartilage Lichen's gray-green ribbons strikingly dangling from branches like tattered lung tissue; Old-man's Beard's windblown threads really looking like an old man's white beard blowing in the wind... On and on, every new lichen species exposes us to something unexpected, maybe something bizarre, but always pleasing and beautiful.
In fact, among the lichens there's such gorgeousness and innovation of form and design that it's clear that something is going on far transcending the demands of mere functionality. Lichens are put together with flair, and passion, and maybe some kind of love.
But, once lichens start you thinking like this you realize that the same can be said of all of Nature. A commonplace tree is more of a wonder than any lichen. If we're not inspired and awed by simple walks through woods or across average fields or down regular beaches, it's because we've grown accustomed to what we're seeing. Familiarity has desensitized us, but that doesn't mean that mind-boggling gorgeousness and meaning isn't everywhere.
So, lichens remind us of at least two worthy insights. First, the Universal Creative Force not only is "productive" of diversity in the Universe, but also the Force creates with elegance, panache and maybe even humor. Second, lichens remind us that we can shake up our own lives simply by taking a fresh look at what's commonplace and normal.
FEATURED ESSAYS FROM THE PAST:
"Sitting in Sunlight" from the December 30, 2005 Newsletter, at http://www.backyardnature.net/n/p/051230.htm
"Wealth" from the March 14, 2010 Newsletter, at http://www.backyardnature.net/n/p/100314.htm
Best wishes to all Newsletter readers,
All previous Newsletters are archived at http://www.friocanyonnature.com/n/.