November 2, 2018
ARMY ANTS ATTACK TAILLESS WHIP-SCORPION
Masses of army ants marauding across the landscape have been turning up regularly lately. Our Army Ant page shows and tells plenty about them at https://www.backyardnature.net/mexnat/armyant.htm
This week just as the sun was setting a roving ink-stain of them passed the hut's porch, just grazing the entry area, and I felt lucky. However, at that moment Katrina the dog was returning from her sunset walk and pranced right into them. It was the first time in my life that I've seen a dog walk backwards.
As always, all kinds of insects, spiders and other invertebrates were either frantically fleeing the onslaught, or else being methodically dismembered, with legs, heads and other body parts being carried forward toward the ant-mass's front. The mass's edge did overlap the pillar-like stand made of adobe blocks where I keep a dishpan of water for washing things off, so ants swarmed up the stand and explored my bar of soap, scrub brush, washrag and dishpan.
To my astonishment, they drove from the washing spot something that in the early evening's dim light looked like a very big, heavily built spider, but a spider with spiny front claws like a scorpion, yet having no curled, stinger-tipped tail as scorpions do.
Immediately I knew that it was a tailless whip-scorpion, because several times empty exoskeletons shed by molting ones have turned up. You can see such an exoskeleton at https://www.backyardnature.net/chiapas/whipscrp.htm
However, this was the first time I'd seen a living one. The camera was lying nearby but the critter was moving so fast that I hardly had time to set up the flash and snap the picture at https://www.backyardnature.net/n/18/181102ws.jpg
There the fleeing arachnid is crossing an ashy area beside my porch-floor fireplace, so that's why everything is ashy gray. The reason the image include such a large expanse of ashes is that it had to be included to show the animal's remarkably long, slender, antennae-like front legs, technically referred to as "antenniform legs." In the picture, the antenniform legs extend to or beyond the image's left and bottom borders.
These super-long, slender legs are the "whips" in the common name "whip-scorpion," and they're used as if they were antennae, to locate prey. Once prey is located, the claws or pincers, or "pedipalps," take over. Below, an enlarged section of the above picture better showing the whip-scorpion's body reveals that this one's pedipalps are carrying an army ant -- or maybe the ant is trying to dismantle the whip-scorpion's mouthparts -- at https://www.backyardnature.net/n/18/181102wt.jpg
Tailless whip-scorpions occupy tropical and subtropical regions worldwide and mainly are found in warm, humid environments, such as leaf litter, caves and beneath tree bark. They feed mostly on many kinds of small invertebrates and possess no venomous fangs or scorpion-like stingers. They're hard to get to bite a finger, but if you persist in poking at them they might grab a finger with their pedipalps and possibly puncture the skin.
In talking about tailless whip-scorpions, we're not referring to any particular species or even a genus. Tailless whip-scorpions have their own taxonomic order. To put that into perspective, all primates from chimpanzees to humans belong to the Primate Order, while all songbirds from warblers to sparrows belong to the Passerine Order. All species of tailless whip-scorpions belong to the Amblypygi Order. In evolutionary terms, that order is considered an ancient one, fossils of them dating back to the Carboniferous Period -- ±359 to ±299 million years ago, well before the dinosaurs arose.
As of 2016, about 155 species of tailless whip-scorpions had been discovered and described. In the Yucatan Peninsula three species are listed, all in the genus Parraphrynus, and I can't say which species this is.
*****
BEAN SLUG
The dry season suddenly has begun, so in the garden I wanted to cover a newly sown bed of cilantro with a trashed plasticized tablecloth, to keep the soil from drying out. When I picked up the tablecloth, on the side that had lain against the earth, an oval, brown lump of flesh about the length of my thumb clung to it, exactly as shown at https://www.backyardnature.net/n/18/181102sl.jpg
Immediately I thought "slug," but slugs tend to have apparent front and rear ends. Here, which end is which? I couldn't find a hint of a front bearing eye spots or tentacles. Hoping to find a mouth I pried off the somewhat sticky-feeling feeling entity and turned it over, finding what's shown at https://www.backyardnature.net/n/18/181102sm.jpg
No mouth there, and what's that slender band of flesh running down the blob's center, like a squashed earthworm? This didn't seem slug-like at all, but then the creature began moving, curling one end around just like a slug.
Assuming that it was a gastropod-type mollusk -- class Gastropoda (snails & slugs) of the Mollusk phylum -- I checked out the various mollusk orders by doing a Google image-search on each order name. Soon a thumbnail image popped up showing a brown blob of flesh just like ours.
It's SARASINULA PLEBEIA, commonly known both as the Bean Slug and the Caribbean Leatherleaf Slug. It's native to tropical America but spreading and introduced in Australia and some Pacific islands, as well is the US deep south, where it's regarded as a potentially serious invasive species. Serious, because the slug eats a variety of important crop plants, including bean, chili, tomato, cucumber and, in Mexico, it's caused severe losses in vanilla plantations.
In our second picture showing the slug's underside, the narrow band down the body center is the foot, while the broader fleshy areas along the side are the mantle. That doesn't help us figure out which end is the front, but I think I got a picture of the anus at the rear end, shown at https://www.backyardnature.net/n/18/181102sn.jpg
Otherwise I never did see signs of a front end, but now that I know to be looking for a more outgoing individual, it's on my list of things to look for.
*****
"AUTOGRAPH TREE"
During my recent camping trip south to El Rosario National Park, on Sayaxaché's east side in northern Guatemala's Petén department, as I explored the park campground's perimeter on September 30, I came upon the pretty sight shown at https://www.backyardnature.net/n/18/181102cs.jpg For a split second I thought it was a flowering magnolia tree, for the thick, leathery, evergreen leaves were magnolia-like, as was the blossom. But, wait: Where are the flower's stamens, and it's stigma, style and ovary? There were none, as you can see closer up at https://www.backyardnature.net/n/18/181102cu.jpg
The "flower" is a mature fruit with its shell splitting into petal-like segments. The orange item made more sense when its top was broken off, shown at https://www.backyardnature.net/n/18/181102cv.jpg
Suspended within the orange matrix, the oblong, yellowish things are seeds; a seed parted from its orange matrix is stuck to my fingertip at the image's top, right. The orange matter surrounding the seeds consists of stuck-together "aril," an aril being a seed's outer covering. When arils are bright and positioned so conspicuously in a fruit, it's to be understood that they are providing a visual attractant to animals that will eat the aril, in the process ingesting the seeds, which the animal then will disseminate into new territory.
Knowing I'd need to "do the botany" later, I looked around for more field marks. Several branches of the 10-ft-high bush or small tree (3m) bore egglike objects that earlier I'd thought were magnolia flowers about to open, but which now I understood to be unopened fruits. One is shown at https://www.backyardnature.net/n/18/181102ct.jpg
Magnolia stems bear stipular rings -- scars left by large stipules that have fallen off -- surrounding the stem at each leaf. This tree's twigs also bore such rings, as shown at https://www.backyardnature.net/n/18/181102cw.jpg
But, these fruits and seeds are not even close to being like those of magnolias. What tricky things Nature can do...
It took awhile to figure out that the mysterious little tree was a member of the tropical Garcinia Family, the Clusiaceae, a family best known for being home to several species producing delicious fruits, especially the Mamey or Mammee-Apple native to and commonly grown in humid, tropical Mexico, and the southeast-Asian Mangosteen.
Our tree belongs to the genus Clusia, but without flowers I can't be sure which species it is. The most commonly occurring and best known species is Clusia rosea, known in English as the Autograph Tree, and our tree's fruits and leaves appear to match fruits and leaves of that species. The name Autograph Tree for Clusia rosea derives from the practice of people scratching their names with their thumbnails onto the leaves glossy surfaces. The damaged tissue whitens and the scar endures, the "autograph" plainly remaining visible
If this really is Clusia rosea, it's a Caribbean species, though because of its prettiness it's been introduced into Florida and other places. Possibly it was planted at the edge of the Rosario National Park campground, or has escaped. The species has become a serious invasive in Hawaii and some tropical countries, such as Sri Lanka. Its growth form is something like that of a strangler fig -- starting out growing on a tree or rock, then climbing into and rapidly overgrowing a tree, eventually killing it and taking its place.
*****
"BIG SENNA"
Also during my recent camping trip south to El Rosario National Park, on Sayaxaché's east side in northern Guatemala's Petén department, on October 1, a conspicuous tree in the park's campground turned out to be a species I've been wanting to see. You can see its substantial trunk and identification sign at https://www.backyardnature.net/n/18/181102cg.jpg
The sign gives its local names as Bucul and Carao, though in southern Mexico the name Cañadonga seems to be preferred. It's CASSIA GRANDIS, a member if the huge Bean Family, native from southern Mexico southward at least to Costa Rica. The grandis in the name hints at why I've wanted to see it. It means "big," yet all the Cassia species I know are small trees, bushes or even herbs. There's no good English name for Cassia, so my "Big Senna" is a made-up one. Often members of the genus Cassia are known as sennas. When you know a few Cassia species, seeing such a big one as this is a real surprise.
The tree's leaves, however, looked like you'd expect of a Cassia, as shown at https://www.backyardnature.net/n/18/181102ch.jpg
Cassia leaves are "even pinnate," meaning that they're once-compound, with an even number of leaflets on each side of the leaf axis, or rachis, with no lone leaflet at the rachis tip.
The campground's Cassia rosea trees were neither flowering nor fruiting, the literature indicating that in our area the species' pink, Redbud-like flowers appear mostly from late February to mid April. At the campground, the tree's huge legume-type fruits must have reached maturity in August or September, because several in various states of decay still lay on the ground on October 1. You can see a couple at https://www.backyardnature.net/n/18/181102ci.jpg
The fallen-away legume wall of the bottom fruit shows empty seed (bean) chambers. Numerous beans in the pod's crosswise partitions is a feature of many Cassia species. By the way, in the picture I'm wearing a jacket not because it was a cold day in Guatemala, but because it helped keep the mosquitoes off.
The sign at the tree's base also said that sometimes Cassia grandis wood is used in carpentry, cabinet-making, floors, posts, rustic furniture, tool handles, firewood, charcoal, for medicinal purposes, and something else I can't read. On the Internet I read that medicinally it's used to cause abortions, as a remedy for various chest problems, and also just as a drink.
*****
WHY SLUGS?
This week while checking out the Bean Slug, the first thought that came to mind was, "In Nature, what can be the use of such a creature?"
This is a sneaky question because the moment you agree to think about it already you've bought into the proposition that things have to be useful to have a right to exist. However, the "Nature as teacher," or "Nature as Bible" concept, with evolving Life on Earth serving as the teaching model, or paradigm, shows us that the question's premise is as senseless as "Why is blue crunchier than green?" The "use" question is as silly as the "crunchy" one because both questions are based on false premises.
The evolving-Life-on-Earth paradigm reminds us that when Earth developed dry land, new lifeforms from the marine environment moved onto the land and began evolving. When mountains appeared, certain creatures arose to occupy the sunny sides, others the shady sides. When trees came along, lichens arose adapted to live on tree bark. When there were lichens, tiny mites living amid lichens came into being. Then came invertebrates that fed on lichen mites, on and on.
The point is that Earthly life inexorably evolves toward ever-greater diversity, with ever-more sophisticated interrelationships developing among those diverse beings, the beings themselves often producing conditions leading to yet new forms of life. The Universal Creative Impulse simply has a passion for diversity and interconnectivity. It's what She "wants," what She "does." She wants it so badly that, in my way of thinking, Her desire is worth recognizing as a Law of Nature.
At this point, the question might arise, "Of what use is this kind of thinking?" This question, applying only to the subset of Nature known as human thought, is a good one. One answer is that such thinking might be "useful" if one day you get around to asking the question, "Really, of what use am I?
Interestingly, this week, the Bean Slug turned out to be useful, after all. That slimy, almost amorphous, garden-eating little brown blob usefully reminded me that we're all -- we stars, rocks, Bean Slugs and such -- part of the Universe's evolving diversity, and that whatever form we've taken, we should feel equally welcome in the sacred Grand Scheme of Things.
If we can accept the validity of mountains and orchids and singing birds, the Bean Slug teaches that very rightly we may accept ourselves with equal magnanimity.
*****
Best wishes to all Newsletter readers,
Jim
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