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

November 17, 2013

BLISTER SPIDER
Two fellows were lowering a submersible pump 300 feet down the well recently dug beside Juniper House, and they had stories to tell. What a world of inexplicable events, conspiracies, and hypocrisies we live in! On the side of our 1100 gallon water tank one of the men spotted a dark little spider about the size of a fingernail, and with awe announced that it was the Blister Spider. Blister Spiders spit venom at you causing big blisters all up your arms and on your face, blisters that are surpassingly painful and don't heal well. While describing the horror of the blisters, the man's hands pantomimed venom arcing through the air and descending all over a victim. Once Blister Spider stories were exhausted, talk drifted to a certain black-and-white, very hairy spider around here that if you touch it shocks you with high-voltage jolts of electricity.

People standing around the well may have had doubts about the electricity spider, but that dark little spider on the tank had been identified by someone who knows his spiders, so people stayed well away from it. Except me; I got so close that more than once the spider jumped onto my camera lens, and onto me. Despite the spider's curiosity, I got the great picture shown at http://www.backyardnature.net/n/13/131117sp.jpg.

A view from the top showing striking patterns on the abdomen and cephalothorax is at http://www.backyardnature.net/n/13/131117so.jpg.

I didn't notice any spigots for spurting venom onto people, but I didn't look too hard because to me this looked like an ordinary jumping spider. But there are lots of jumping spider species, so the picture was sent to volunteer identifier Bea in Ontario, who quickly decided we probably had a female Carolina Jumping Spider, PHIDIPPUS CAROLINENSIS. Despite the "carolinensis" in its name, it occurs in Texas and parts of Oklahoma and Kansas, and Mexico. To confirm the name the pictures were uploaded to the Arachnoboards.com spider-ID forum where we asked if anyone disagreed, and no one did.

It's true that jumping spider venom is powerful stuff; often you see them subduing surprisingly large prey. However, they're so small and their mouthparts are so miniscule that they're no problem for humans, plus they show no interest in attacking us -- though if you get as close as my camera lens did, just an inch or two away, they might jump on you, maybe just for fun. Jumping spiders don't produce webs but they do use silk to build cocoon-like retreats for themselves and egg casings, and as they wander about they leave behind silken safety lines.

*****

HARVESTER ANTS
A common and conspicuous feature of our local landscape is a spot of bare ground about the size of a small bathroom surrounded by normal vegetation, with a single hole in the center of the bare ground wide enough to poke a finger into. You find these in the middle of seldom used gravel roads, abandoned lots, lawns, city parks, in pastures, grassy areas along cliffs -- just about any open, dry area. You can see such a barren spot in the middle of a large field of invasive King Ranch Bluestem near Juniper House at http://www.backyardnature.net/n/13/131117an.jpg.

This is the entrance to a colony of harvester ants. You can see the large (ΒΌ-inch, 6mm), reddish ants entering and leaving the hole at http://www.backyardnature.net/n/13/131117ao.jpg.

In that picture notice that a little away from the hole the ground is littered with husks of grass grains and other dry plant material. A close-up showing ants at the hole is at http://www.backyardnature.net/n/13/131117aq.jpg.

A close-up of an individual ant appears at http://www.backyardnature.net/n/13/131117ap.jpg.

One feature distinguishing this species from some others -- Bea in Ontario says that we have ten harvest ant species in Texas -- is the pair of small spines at the rear of the large body segment (thorax) immediately behind the head. We're assuming that this is the common species in our area, the Red Harvester Ant, POGONOMYRME BARBATUS.

As with most ant species, winged male and female harvester ants live in the nest until weather permits them to fly away and mate. After that, usually the male dies, but the newly-fertilized queen flies away and chooses a spot for her new colony. She sheds her wings, digs a hole and begins producing all-female "worker ants." She keeps at this for up to twenty years until her death; some queens have been known to live up to 30 years in the wild.

Workers forage around the nest for seeds, which they store in the nest's underground chambers. One nest has been reported to extend 15 feet deep (4.5m) and contain 436 chambers. Three to eight trails typically lead away from the mound. Scout ants are the first to leave the nest each morning. When they find food they mark their return path to the mound so that workers can follow the scout's scent to the food. Other worker ants clean, extend and generally tend to the mound, the queen and the brood.

If you've every had a commercially supplied ant farm there's a good chance that your ants were Red Harvester Ants, who are considered ideal for the purpose because of their large size, the interesting way they store seeds in chambers, as well as their inability to climb the farm's glass walls.

Though folks around here don't seem too concerned about their presence -- while photographing them I got them all over my body and camera without being stung or bitten -- I read that harvester ant workers of the genus Pogonomyrmex (ours) possess the most toxic venom to mice documented in any insect tested so far, comparable to cobra venom. Since we don't hear of people succumbing to harvester ant stings, the ants must rarely bite, and not inject much venom when they do.

Red Harvester Ants are found in the US Southwest, from Oklahoma, Kansas, New Mexico and Arizona south into Mexico.

*****

COCHINEAL
Pricklypear cacti are abundant here and occasionally you spot a plant whose spiny, green pads are spotted with small tufts of white, cottony fuzz, as shown on a Texas Pricklypear, Opuntia engelmannii var. lindheimeri, at http://www.backyardnature.net/n/13/131117ch.jpg.

If you look closely at an individual tuft, often you see that the white cotton is stained here and there with red, as you see at http://www.backyardnature.net/n/13/131117ci.jpg.

If you carefully remove a tuft and pick apart the cottony fibers, inside you may discover a tiny insect like the one shown at http://www.backyardnature.net/n/13/131117cg.jpg.

In that picture notice the blood-red stain on the tip of my thumb at the lower left. That resulted from a previous attempt to tease the insect from its cotton, when I was not careful enough, and the insect got a little squished. A bright red liquid issued from it.

All these details bring up a good story.

First of all, the insect is one of several species of the scale-insect genus Dactylopius. Probably it's the common species, DACTYLOPIUS COCCUS, but it's hard to distinguish the species, and other species also occur here. Scale insects in general vary dramatically in appearance; some hide beneath oyster-shell-like wax scales, and some others form cottony tufts like ours. Those with cottony coverings often are called mealybugs. The various coverings protect the insect from detection by predators, temperature extremes and, if they are on a plant in a garden or greenhouse, from insecticides sprayed on them.

I'm unsure whether the insect shown in our last picture is a larva or an adult female. That's because among scale insects the adult females continue to look as they did when they were larvae, a condition known as "neoteny." Adult males of most scale species have wings but they never feed, just try to have sex with a female, then die within a day or two. An upshot of neoteny among females is that females are immobile because they have no typical insect legs -- or eyes or antennae, for that matter. Being immobile must add some complications with regard to reproduction because often, especially late in the season, their offspring are parthenogenetically produced without the help of males. Their offspring are genetic replications of themselves.

So, an egg is deposited on a pricklypear, the egg hatches very quickly, and the first-instar, grub-like larva emerges. These first-instar larvae bear rudimentary legs and can crawl about; they're called "crawlers." On their heads they also bear long wax filaments that, when caught in the wind, enable the larvae to be blown to other cacti. Once they find a good place, they begin sucking the pricklypear's sap. After the first instar they lose their rudimentary legs and become fixed in their location for life -- throughout both their larval and adult stages -- and they develop the cottony material that covers them.

Certain mealybugs of the genus Dactylopius are famous less for their interesting life cycle than for the red juice they're filled with. Long before Europeans arrived, indigenous American cultures were using the red juice from Dactylopius mealybugs as a spectacularly red dye. The juice contains carminic acid which when mixed with aluminum or calcium salts make an exceptionally vibrant carmine dye known as cochineal.

During the early days of the conquest, Europeans paid high prices for cochineal dye; by 1600, cochineal had becom Mexico's second most valued export after silver. The dazzling splashes of red in paintings at that time by such artists as Rembrandt consist largely of smashed female Dactylopius mealybugs and eggs. Wikipedia's interesting page on cochineal dye is at http://en.wikipedia.org/wiki/Cochineal.

The main Dactylopius species producing cochineal is our Dactylopius coccus. Curiously, one population of this species occurs in South America while another is in Mexico. Recent genetic studies indicate that D. coccus originated in South America, but presumably was carried to Mexico by humans who valued it as a source of red dye.

*****

PALLID-WINGED GRASSHOPPER
There's a huge world of grasshoppers, and they can be hard to identify. For example, the other day after a night when it nearly frosted a smallish grasshopper turned up basking in early morning sunlight. Usually when I try to get close enough to a grasshopper for a close-up they jump, but this one didn't. I figured he'd gotten cold in the night and maybe was stunned. The resulting picture is at http://www.backyardnature.net/n/13/131117gh.jpg.

As that picture was snapped, the poor grasshopper fell over. He wasn't dead because his legs had been moving, so I figured maybe the night's cold had numbed him more than I'd thought. I further thought that with such an immobile grasshopper, maybe I could get a picture of the wing color, for that's often an important field mark. Picking up the critter and spreading his wings, I got the picture appearing at http://www.backyardnature.net/n/13/131117gj.jpg.

With such a cooperative subject, it was also easy to snap the fine face picture at http://www.backyardnature.net/n/13/131117gi.jpg.

It was clear that with such short antennae our friend was a member of the Short-horned Grasshopper Family, the Acrididae, and with the colored bands on the back wings he further belonged to the Band-winged Grasshopper Subfamily, the Oedipodinae. However, at that point identification gets sticky. Bea in Ontario and I thought it might be a Threebanded Grasshopper, genus Hadrotettix, but we were so uncertain that we uploaded the pictures to BugGuide.Net's ID forum, where eventually an expert let us know how wrong we were. We had the Pallid-winged Grasshopper, TRIMEROTROPIS PALLIDIPENNIS, commonly occurring from British Columbia, Canada south through the western half of the US, to Argentina in South America. Pallid-winged Grasshoppers are the most widely distributed band-winged grasshopper in the New World.

By the way, one feature that with my blurry vision I hadn't even noticed until he was on the laptop screen was that our grasshopper was missing his back jumping leg. No wonder he fell over!

Pallid-winged Grasshoppers eat many kinds of herbs, grasses and shrubs, especially in places where there's plenty of bare ground on which to bask and rest. Often they turn up in weedy city lots. Sometimes their numbers suddenly skyrocket, creating grasshopper plagues of biblical dimensions. In huge numbers they can defoliate nearly all wheat plants in a field, and nibble off their heads. They can consume a cotton field to ground level. They've invaded and damaged fields of safflower and grapes as well as cotton, sugarbeets, barley, and corn.

In April of 1998, in west-central Arizona, during the night swarms of Pallid-winged Grasshoppers were attracted to city lights, where street traffic crushed them, causing such a mess that cars and trucks skidded and slid. Accumulations of grasshoppers around buildings reached a depth of two inches (5cm).

You can read much more about this interesting grasshopper on their USDA page at http://www.sidney.ars.usda.gov/grasshopper/ID_Tools/F_Sheets/pallidwg.htm.

*****

TRIDENS GRASS
Here at the edge of the prairie grasses are abundant and diverse. It's easy to start overlooking them, hoping to see herbaceous wildflowers. Still, from time to time a unique grass catches the eye, and that's what happened this week with the grass shown along a seldom used road, at http://www.backyardnature.net/n/13/131117tr.jpg.

Admittedly, in the picture it's not so spectacular, but if you draw close and look at the spikelets you'll see unexpected elegance, shown at http://www.backyardnature.net/n/13/131117ts.jpg.

The spikelets are very flatly compressed, with the backs of the scales, or lemmas, of individual florets forming sharp ridges. Each lemma bears three well defined veins -- one vein on each side of the sharp-backed midrib -- and a hint of raspberry color. A close-up of individual florets -- the lemmas up to 5mm long -- can be admired at http://www.backyardnature.net/n/13/131117tt.jpg.

I'd never seen this grass, so to identify it its ligule -- the flange-like affair at the blade's bottom where it meets the stem -- had to be photographed, and it turned out to be an interesting one, shown at http://www.backyardnature.net/n/13/131117tu.jpg.

The ligule is a very hairy, collar-like membrane. That's unusual, because many grasses have no ligule at all, and those that do usually produce ligules that either are membranous or consist of a wall of hairs, but this one is both membranous and hairy. Also, a good field mark for this species is the narrowness of the blade -- only about 2mm wide (1/16th inch) -- and how the blade tends to curl in on itself, forming a cylinder, as it dries. Also, notice that, except for the ligule hairs, other parts of the blade and sheath below the blade are hairless.

Originally I keyed out this grass to Buckley's Tridens, Tridens buckleyanus, endemic just to Texas's southern Edwards Plateau area. However, Bill Carr, who knows the Texas flora much better than I, wrote saying that to him it looked like Wilman Lovegrass, ERAGROSTIS SUPERBA. Bill writes:

Wilman lovegrass (Eragrostis superba), an Old World grass that was introduced to Texas a few decades ago for the usual reasons -- erosion control, etc. It was widely planted by the Lower Colorado River Authority in its projects in that watershed, and it's now fairly common on sandier soils of river terraces. On one hand, it's not native to Texas (though not the most aggressive exotic grass in the state), but on the other hand I have to admit that it is a beautiful grass.

*****

BELIEVING IN BLISTER SPIDERS
Before the water pump fellows told their blister spider stories, no one standing around the wellhead would have said that in our area it's possible for a spider to exist capable of splattering blister-causing venom onto people's arms and faces, else we would have heard of it by now. Moreover, they'd have agreed that common sense says that such a small spider as the one on the water tank couldn't possibly expel such large amounts of venom over such long distances.

Yet, the blister spider stories were believed. Even the story about the black-and-white, fuzzy spider that delivers electrical jolts left everyone wide-eyed, at least at first.

Maybe our gullibility for such stories was hardwired into us, in our genes. Children believe most anything told to them by adults, and you can see how this would be adaptive for our species, and normally desirable. We all know that sometimes adults need a break from acting like adults all the time, so, at the wellhead, believing in blister spiders was like learning about the Tooth Fairy.

Since normally people don't like to be ignorant about the world around them, in general humans are predisposed to enjoy learning new things -- even if the learning comes from a doubtful source. Scott Lilienfeld, assistant professor of psychology at Emory University, says that "We have an adaptive reflex to make sense of the world... We need this ability, because the world is such a complex and chaotic place... "

Moreover, even if what we learn comes from a shady source, sometimes we use mind tricks to help us keep believing what we want to believe. Tory Higgins, chair of the psychology department at Columbia, says, "Once you have a belief, the way you look at evidence changes. When you search your memory, you are more likely to retrieve information that will support it and avoid exposure to information that will disconfirm it."

So, several guys standing around a wellhead were naturally disposed to believe stories about blister spiders and spiders that produced electrical jolts. There's an innocence about it that's almost touching. Yet, there's also danger in this kind of thing.

For, now that it's clear that we humans can destroy Life on Earth, it's fair to ask whether we still have the luxury of being so gullible about things others tell us. For the first time in human history we realize that we're living on a tiny, isolated and fragile planet suspended in an awful expanse of hostile space, so do we keep living our individual lives like always, doing what everyone else is doing, doing what everyone else says we need to do?

It seems like the smart thing for each of us to do is to reassess what we eat, where we set the thermostat, how far from work we live, etc. in terms of whether they're sustainable or not. And this rethinking process should not admit wishful thinking or fantasies of any given political faction, religion or fad belief.

The world is thick with folks talking about blister spiders and the like. To save Life on Earth we listeners have to keep in mind our own naturally gullible natures, turn away from the story tellers, and act instead on what we see with our own eyes, understand with our own minds, and feel deep within ourselves.

*****

FEATURED ESSAYS FROM THE PAST:

"The Meaning of Life" from the May 11, 2003 Newsletter, at http://www.backyardnature.net/n/p/030511.htm

"Wendell Berry & the Maya" from the October 31, 2010 Newsletter, at http://www.backyardnature.net/n/p/101031.htm

*****

Best wishes to all Newsletter readers,

Jim

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