Hemileuca sororia is another species that's not been very clearly documented. For one thing sources disagree on whether it's sororia or sororius. Sororia is far more often used, but some sources list both.
Google does provide enough evidence to explain this. Early naturalists were sometimes too hasty to describe a single specimen as a new species, when it might have been merely a variant form of a more common species. Males and females of dimorphic species were sometimes reported as different animals. Hemileuca sororius was reported first, from an individual found in western Mexico. H. sororia was described a little later, from individuals found in eastern Mexico with a look similar to what another naturalist had read about sororius. Still later H.G. Dyar reviewed the available literature on the Mexican and border Hemileucas and said that, as nobody had provided further documentation that sororius was a distinct species, that name should be dropped from lists. Most but not all sources have dropped it. Not all have even kept sororia; most sources do list sororia but few writers in English have anything to say about it. It is sometimes found in border States but is basically a Mexican species.
Both names are atypical for this genus. Earlier Hemileuca species names commemorated goddesses that were actually worshipped; later ones commemorated places or people, like other recent species names. "Sonora" would have been a logical name for a species found there, but it wasn't used. Sororia and sororius mean "sister's," but although the ancient Romans worshipped many abstract ideals, and had an ideal of Brotherhood, I've seen no information (even among feminist goddess studies) suggesting that they ever worshipped Ssterhood. The ancient Romans gave brothers some legal responsibility for each other but expected sisters to be separated by arranged marriages into different families, and to have no power to carry out any responsibilities. So why should there be a Sister's Hemileuca? Presumably some naturalist thought he was honoring his sister, but the story of this species' name is undocumented.
Perhaps it should be. Few sisters would want to have stingingworms named after them.
Several sources expressed the opinion that the rose-brown form of sororia is especially pretty. Moth fanciers tend to be people who admire subtle variations in patterns of brown and gray, and this color scheme is the type that pleases their eyes:
Photo by Suecar. It's a girl--we can tell the moth is female by her egg-stuffed body shape and flat antennae. Females are a little bigger than males, but not so much that this photo really tells us the size of the moth photographed. Knowing that the moth's wingspan will be a lttle over two inches tells us that Suecar has dainty little hands.
The scope of study of this species may disappoint moth lovers. Nineteenth century naturalists didn't find many, or breed any, before attaching themselves to opinions about how this reddish, sometimes pale moth might be related to Hemileuca dyari, H. oliviae, or H. hualapai. The great Harrison G. Dyar described it as H. oliviae race sororius. What Google would later call Thomas Cockerell's one-page "book" about it was less than a full-page entry in the annual science magazine Psyche, in which he called sororia a "race divine" and said that it was "so large and so dark" he couldn't believe it was the same animal as H. oliviae.
Right. Because you think a moth is "beautiful" you want to dissociate it from H. oliviae, which is, more because of its horrid habits than because of its otherwise cute fur-mop face, agreed to be an ugly, nasty moth? Very scientific. Not! Sororia does share the fur-mop face; it has a head, though the head is small since it has to contain only eyes and antennae, but the eyes don't usually show. The moth is protected from decapitation by looking as if it might already have been decapitated. If a moth has antennae, however, it does have a head--perhaps a small one if, being a silk moth, it has no mouth.
Cockerell thought sororia was related to sororius, which he had apparently seen only as descriptions in books, and hualapai, which MIT's free copy of Cockerell's document computer-scans as "kwalafai." Other words are grotesquely misspelled as MIT's computer tried to scan an older typefont as Times New Roman. "New" appears as "hXW."
Anyway, to prove that sororia was different from oliviae, dyari, or hualapai we would normally want to rear specimens and see whether they ate the same or different food, whether siblings who ate different food looked or behaved more like those other species, whether adult moths would willingly mate with each other and, if so, whether they produced viable offspring. Apparently none of this has ever been done. Science accepts sororia as a distinct species because it looks like the fresh original of which the other red-skinned, white-furred-and-scaled moths are faded copies. Mexican scientists probably know what the egg, larva, and pupa of sororia look like but they don't seem to have documented online whether these early stages show any consistent difference from the other species.
H. sororia looks more like the Mexican Hemileucas that live nearer to it, H. lex, H. marillia, and these may form a single super-species for all we know. It may be that sororia/sororius from the opposite coasts of Mexico looked more like each other than like Hemileucas found further inland merely because they ate plants that grew closer to salt water.
Dyar's lumping all the reddish-skinned Hemileucas together with H. oliviae, at the time when he did it, amounted to condemning them without a trial. Everyone agrees that H. oliviae went through an alarming population explosion about a hundred years ago. Crowding apparently induced a change in typically bland, even polite-looking, Hemileuca behavior; caterpillars that normally behave as if they liked each other were showing hostility, making what might have been threat displays or serious efforts to sting each other. (All stingingworms do deliberately turn their venomous bristles toward a possible threat, and toward any surface on which they land if they fall, but it's not clear whether the little dumb animals know they can sting. They may only know that they're protected from being crushed by their stiff bristles.) Caterpillars that would normally allow themselves to be picked up, crawling curiously over an observer's hand, would roll and squirm vigorously as if trying to sting the observer's hand as badly as possible. Claims were made by sober, apparently scientific, observers that these caterpillars' population density was ten times what it is in favorable conditions now, which would explain their apparent hostility; at that level of crowding many animals that are normally social become cannibalistic. When ranchers saw these dreaded, detested vermin crawling up corn stalks, they panicked, especially as the caterpillars were probably starving and probably did nibble on corn leaves after crawling up cornstalks to get off the hot sand on hot afternoons. By all accounts they ate a lot of things they were unable to digest, and many died of starvation anyway.
The normal human instinct to kill stingingworms on sight was thus exacerbated as oliviae became a plague. People wanted to cover fields in arsenic to annihilate the little monsters. This unjustified hostility spilled ove onto all of the Mexican species, though even today nobody seems to know for sure whether they eat grass or, if so, what kinds. They do not eat corn. Populations are usually kept low by natural predators. Most birds and mice don't see stingingworms as edible; a few species can eat them, but no species eats very many. Tiny flies and wasps, however, get inside the caterpillars, often a whole brood inside one caterpillar, and devour enough of its insides that is can't mature and reproduce. Loss of predator population was what made Hemileuca oliviae a terrible plague.
Whether the Mexican species were overpopulated even at this period is unclear. Any animal that is covered from head to tail in bristles, each one of which does about as much damage as a bee sting, does not have to be present in plague numbers to be a nuisance. One stingingworm is a nuisance. However, if sororia or sororius ever was a plague, or even common, no evidence of it has been preserved online.
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