"Shinnery oak" is one of those words that seem to have two meanings. Originally it was from the French words chene (properly written with a circumflex accent), an oak tree, cheniere (properly written with a back-slanted accent over the second E), an oak grove. Shinnery oak is a scrubby little shrub, similar in some ways to the big oak and beech trees, but much smaller. Its name sounds as if it meant something that would skin your shins if you walked or rode a horse through it.
In fact some people use "shin" and "shinnery" in English just like chene and cheniere in French when they talk about this species. "One or two shins in the shinnery seemed completely defoliated."
Photo from the Morton Arboretum.
Not only would these "shins" skin your shins; in spring they might be infested with large bristly caterpillars, each bristle tip on each of which contains about as much venom as a bee sting.
Shinnery oak grows where not much else will grow; it can be good ground cover. It becomes toxic to animals that eat very much of it, though. In addition to harboring stingingworms in summer, its leaf litter shelters cotton boll weevils in winter. If the shinnery oak has reclaimed enough soil that grass will grow, and you want to raise cattle on the land, you want the shinnery oak gone. It's woody and would make good fuel, but in the twentieth century people in Texas and Louisiana had more fuel than they knew what to do with. They'd set fires to burn the shinnery oak out of a field, then sow grass and hope the grass would hold down the soil. Shinnery oak is tough stuff and evolved naturally in an area that sees lots of brush fires. The farmers tried spraying herbicides on it. That created a Vicious Spray Cycle. They tried defoliants. Shinnery oak is normally defoliated by H. slosseri, and survives. At the most recent report the farmers were trying running the brushes through shredding machines. That helps to thin it down, but the wood of even scrubby bushes in the oak and beech family is hard on blades.
There was a problem. Well, actually, there were problems, plural, but the problem that relates to our subject today is that Hemileuca slosseri lives in symbiosis with shinnery oak. Burning the shinnery oak was killing a moth, which looks almost exactly like Hemileuca maia, and its caterpillars, which look different from maia but are still unmistakably stingingworms. Getting rid of one nuisance species gets rid of another nuisance species? That's a problem?
Assuming that it wants to live--and at no stage of its life does the moth show enough intelligence to prove that it has a real preference in the matter--Hemileuca slosseri may thank religious people. Humans living in places where the local stingingworm population has died out do not miss stingingworms at all. Humans who care about keeping this species alive are likely to be people who believe that, as God's stewards, we should not allow any of God's other creatures to go extinct.
I believe that, when we encounter stingingworms, our natural instincts are generally healthy. We should try to avoid stepping on them. Bristle tips can stick in shoes, from which they might get into cars or even houses. We should use sticks or stones. Thinning nuisance species--without starting a Vicious Poison Cycle--helps them evolve healthier tendencies to avoid humans.
However, there is concern about the possible extinction of Hemileuca chinatiensis, H. peigleri, and H. slosseri. In some parts of Texas these species are protected, as are two of the western Automeris species. So far nobody seems to have tested whether, if ordnary H. maia were raised on shinnery oak, they would look and behave just like slosseri. Once grown up, they are unlikely to crossbreed, since their reproductive parts develop different sizes and shapes, but whether this is determined by diet or by heredity seems uncertain.
The State of Oklahoma has listed both H. slosseri and the shinnery oak as species of great ecological concern. Neither was ever abundant in Oklahoma, for which one might have thought the people would have had enough sense to give thanks, but...
Nor has adequate research been done on whether, if the federal government takes a firm line on its having no constitutional authority to meddle in what takes place within a State, the farmers can reach a sensible agreement about their nuisance species. Without asking anyone else's help or permission farmers might be able to work out, like adults, where to allow shinnery oak to reclaim otherwise useless land for a few years at a time, and where to grub it out, turn the wood into chipboard, and plant grass and clover. They might even be able to avoid the monocropping that allows the boll weevil to become such a menace. Many human beings, even if male, are capable of making responsible choices if they are allowed to take responsibility. When other people are drawn into the matter, and compromises are made, they go wrong.
Of those who believe that every species has a right to exist, it took no less a name than Roger Peterson's to plead the case for shinnery oak. In this monograph Peterson described the birds and small animals that benefit from this nuisance plant, presumably as shade and/or cover in which to hide from predators.
He did not mention glyphosate among the herbicides people have tried to use to get rid of shinnery oak. They have tried it. In 1985 J.E. Slosser reported that, although glyphosate appeared to have killed the plant, shinnery oak grew back fast enough that glyphosate spraying did not affect the number of boll weevils using the shinnery. It took a nastier poison called tebuthurion to slow down the growth of shinnery oak enough to reduce the number of boll weevils crawling out of it in spring. Tebuthurion remained the chemical most often used on shinnery oak, starting a Vicious Poison Cycle that drove ignorant people to look for even deadlier combinations. Combinations of highly concentrated glyphosate with tebuthurion have been tried, too, but no other way to get rid of unwanted plants has ever been found to be more effective than digging out the roots. Which, in shinnery oak country, is not only hard labor, but also likely, if done on the scale cotton farmers might prefer, to make coastal Texas another "dust bowl."
Peigler and Stone, when they registered Hemileuca slosseri as a distinct species, named it after J.E. Slosser in 1989.
Slosser was still alive and wrote the definitive study of "his" moth in 2001. By that time it should have been published online, and so it was, but neither of the two science sites that have copies will let you read or download it free of charge. A search for Slosser's Biology of Hemileuca slosseri will yield a list of other documents that cite it as a reference.
Back to the moths. Hemileuca slosseri is classified as a Saturnid, a member of the Giant Silk Moth family. In that family it's very far from being the biggest and showiest member--in fact it's near the opposite end of the scale--but it's a fairly noticeable moth. Wingspans average about three inches, give or take a half-inch. The wings get their shades-of-gray coloring from tiny scales. The scales wear off more easily than most moths' wing scales do, so the moth can look translucent or even transparent.
Photo from naturalista.uy. Hind wings showing through fore wings is typical for Hemileucas.
Actually the moths not only look very similar to H. maia, but also to H. artemis, H. nevadensis, H. lucina, or why not just say the majority of all Hemileucas. Peigler and Stone described typical differences in a definitive paper about H. slosseri, but these differences are slight in the most typical individuals and leave many individual moths in the "too close to call" category. H. slosseri tends to have somewhat longer, narrower, more transparent wings.
Photo by Erin_millican. This one's wings do look longer and narrower than H. maia's normally look, to me. Many individuals photographed online do not show this distinction.
Though the wings are often pale and drab, the body fur may show vivid warning colors. If this moth thinks her antennae and front leg may look like the jaws of something that can bite predators back, she's probably pleased.
Photo by Geraniumsmile.
However, DNA studies find differences between some Hemileucas that look and behave alike, greater than the differences between some that seem consistently different. Hemileuca slosseri seems to be a similar-looking yet distinct species from H. maia, but the genetic differences are small:
"The Saturniid moth genus Hemileuca (Walker)," Daniel Rubinoff asserted confidently in 2002, "represents an excellent system for examining character evolution." Even then, in his confidence that a study of the Hemileucas would yield a clear Darwinian progression, perhaps from H. oliviae to H. hera, Rubinoff refused to consider H. slosseri, H. sororia, or H. lucina. What he found was so different from what he seems to have expected as to support the hypothesis I find so easy to imagine--that the Hemileucas were Intelligently Designed by an intelligence that looked forward to a good laugh at Daniel Rubinoff's expense. That the Hemileucas have evolved, perhaps from half a dozen ancestral species, I can believe. That they or anything else evolved as facilely as the fossils Darwin arranged in an order that supports his theories, I'd need to be convinced. Why slosseri don't thrive on the big oak trees maia eat, but only on these oaklike bushes that rarely grow higher than a man's head, is the sort of questions humans may never be able to answer completely. What we do know is that their defoliation of a "shin" here and there probably limits the expansion of the shinnery. This may make slosseri the only Hemileuca that reliably does something useful for humans.
More recently Julian Dupuis had a crack at understanding how the Hemileucas evolved:
Real Science, of course, recognizes that although trying to imagine how things came to be may be fun, it is not scientific. Real Science studies how things are.
The number of eggs a Hemileuca moth lays in one place vary consistently in proportion to the size of the host plant she chooses. Instincts tell moths to lay fifty or a hundred eggs on a big tree, ten or twenty on a small plant. H. slosseri egg clusters have been counted containing more than fifty eggs but more often contain only ten or twenty.
Photo by Nathantaylor.
Hemileucas don't eat the hard, dry shells from which they've just hatched. H. slosseri leave their eggshells on the twigs where they hatched. The shells are still there next spring, and another mother moth may lay her eggs close to the old shells, apparently feeling that at least the site was healthy enough to get those eggs hatched. Or she may not. The proximity of different clusters of eggs on the same twigs made people wonder about this. Moths seem to choose egg sites based on the size of the twig and availability of leaves, not showing a clear preference to lay eggs near old, hatched eggshells. However, eggs laid near fully hatched clusters of eggshells did seem to be the best placed; they were more likely to hatch than eggs not laid near a previous cluster in which all the eggs hatched. It may be that the reason why moths reuse twigs, in the first place, is that they tend to be crowded together in a small shinnery.
The life cycle is timed to fit a hot climate. Caterpillars hatch in April, when leaves begin to open, and et until June. Often they defoliate an entire shrub. Deciduous trees usually have reserves that allow them to refoliate, and since shinnery oaks are seldom defoliated by frost they usually survive the caterpillars' depredation.
Hatchlings are blackish, like most Hemileucas.
Photo by Alex_cicindela_guy.
Photo by Nathantaylor. Second and third caterpillar skins start to show yellow.
When they're old enough to strike out on their own the caterpillars are usually pale yellowish white with black and/or white bristles. In the final instar they may show some black or brown speckles on the skin, in between their bristles, or none.
Photo from naturalista.uy.
But they can be more colorful.
Photo from naturalista.uy. This is not a species that needs to worry much about being eaten by birds, though once in a while one is.
The caterpillar's body is about the same size as most of the large, not gigantic, North American caterpillars--seldom much more than two inches long, not all of three inches. It takes up more space than they do, however, because of its bristles.
The caterpillars aren't intelligent enough to avoid their primary predator, a small fly in the genus Leschenaultia, family Tachinidae. It looks like a very small housefly but it leaves humans and their food alone. Mother Leschenaultia lay their eggs on leaves of shinnery oak. The leaves are tough and uninviting, but that doesn't matter; the little maggots aren't going to eat the leaves. They are going to sit there in the egg form, waiting to be swallowed by a caterpillar. Any caterpillar that eats shinnery oak leaves will do. In the caterpillars' digestive systems, the maggots will hatch and stay inside the caterpillar, eating most of its food, until they're ready to gnaw their way out through the caterpillars' skin and pupate in between the bristles. A caterpillar who has been parasitized by tachinid flies may live long enough to pupate but is very unlikely to survive pupation.
To encourage tachinid flies and other natural pest controllers, simply stop spraying the field. (Yes, "herbicides" and "fungicides" can kill insects; they can kill humans too. Try transferring species that get in the way of the main cash crop into a separate field where the natural ecological balance can be preserved. Tachinid flies, and other creatures that can eat stingingworms and live, will follow the scents of leaves, blossoms, or other insects.
So far as is known, all of the caterpillars that hatch in April pupate in June (or late in May) of the same year. When they emerge from their pupae is anyone's guess. In litters reared together under what seemed to be optimal, certainly identical, conditions some moths emerged from their pupae in November of that year and others in the Novembers of the next two or three years.
Photo by Nathantaylor. Preparing to pupate, the caterpillar burrows into warm dry sand.
No points for guessing where they normally pupate. In the leaf litter under the shinnery oaks, along with the boll weevils. A farmer who shovels up and burns the leaf litter can rid the world of several nuisance insects at once. Hemileuca pupal shells are usually found near, sometimes attached to, the last caterpillar skin, and the bristle tips still sting. It takes more than one year for Hemileuca caterpillar skins really to brteak down into the soil.
Photo by Nathantaylor.
Most of the males in this species seem to hatch in the first cool days of November. Females hatch at a steady pace throgh November and December. Reasons for this difference are unknown. On the surface it seems to favor the male moths' preferences, giving some older male moths a chance to mate with two or three young females. It may also reduce the reproductive rate, since it means that females who emerge late are less likely to find mates at all.
Moths usually mate on stems of their host plant where they can cuddle up face to face. The silk moths don't even eat; they emerge from the pupal stage to mate and die. The Hemileucas live longer than some of the bigger silk moths, up to ten days rather than up to five.
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