How many species are in the genus Hemileuca? Depends where you look. Funet lists 57 species names, and some authorities add a few more, but at least half of them have long been regarded as synonyms (two or more naturalists "discovered" the same moth close to the same time). Some others are known only from specimens found in Mexico or further south; they may still exist, somewhere, but little is known about them. Passing right over H. arizonensis, which was soon agreed to be the same as H. nuttalli, we come to H. artemis. Scientists disagree on whether artemis should be considered a separate species or a sub-species. It's one of the confusing Western "sheep moths" that are found where sheep graze. It's the one that can have very showy black-on-white forewings and black-on-orange hindwings.
Or not.
W. Holland, whose Moth Book was the definitive work on the subject in the early twentieth century, accepted only eight Hemileuca species and regarded artemis as a synonym for nevadensis, of which some still call it a sub-species. He observed that it "closely resembles" H. maia in having wings that can look translucent, almost scaleless. Individuals photographed usually have colorful wings but, in real life, the wings can look worn, or as if the scales failed to develop. Or the wings can be covered in scales, but the colors can be muted, as in the museum piece shown above. He also mentioned that the western Hemileucas tend to have a wider transverse band across the forewings, and more orange color on the tail end.
Holland was the sort of naturalist sometimes called a lumper--the kind who lump similar lifeforms into one species if they're able to crossbreed. More recent naturalists have inclined to be splitters, who split genera into species when they find a consistent genetic type. Holland regarded all the eastern Hemileucas as "local variants" of H. maia. A more recent researcher carefully noted finding, in two parts of Tennessee one of which included Kingsport and Bristol, Hemileuca maia, H. lucina, H. peigleri, H. burnsi, H. artemis, H. nevadensis, H. slosseri, and one of the Bogbean Buck Moths whose classification has been a point of recent debate. If accurate, this study found that "Western" Hemileucas may cross the Missisippi and be found in East Coast states. Or, as with dogs, wolves, and coyotes, the DNA may be complex enough that individuals who vary widely in size, shape, and color may really belong to one immensely diverse species.
The splitter who claimed to have "resurrected artemis from synonymy," or proved that artemis is a distinct species from nevadensis, was the same Richard S. Peigler for whom H. peigleri is named. (In the same 1989 paper, although someone else had described and named H. peigleri, Peigler discussed evidence validating the claim for H. peigleri's status as a separate species.) He said that although both artemis and nevadensis eat native willow leaves, and the moths can look very much alike, the caterpillars are consistently different. Artemis eggs and caterpillars were sometimes found on Salix longifolia (a native willow species; their primary host plant was Rio Grande Valley cottonwood. This cottonwood species, and the moths, are usually found near the rivers that flow through the western desert, but H. artemis is also found near rivers in grassland areas.
Even within a litter the colors of Hemileuca caterpillars can vary, but this pale yellow color distinguished cottonwood-eating artemis from willow-eating nevadensis.
Evidently a kindhearted man, Peigler was concerned about the survival of his stingingworms. They require a lot of sunlight to survive, and are apt to die of a virus infection, as well as fungus and parasite infestations, in damp weather. Populations of H. artemis seemed to be declining in 1989, although in the 1960s the little loathlies had been numerous enough that people demanded spray poisoning. Parasites and predators introduced in the coastal states to control gypsy moths (he didn't say "Virginia," but yes) linger in the ecosphere after the gyps have died or survived, and attack silk moth caterpillars too. H. slosseri also seemed to be threatened by Texans' natural inclination to get rid of shinnery oak, an inconvenient species even when not full of stingingworms.
"Clearly there are numerous and varied conflicts between continued existence of
these moths or their habitat and the social attitudes and demands of civilization. We
hope that none of these species will become threatened or endangered before steps are
taken to stem the tide, because by that time it may be too late," Peigler wrote.
Ordinarily I care about extinction, but in my part of the world stingingworms went locally extinct in the early twentieth century due to logging. Older people still warned kids about them but nobody was sure what they were. In fact my interest in the whole topic of caterpillars, which I don't particularly like, was piqued when some school friends thought a harmless Eastern Tent Caterpillar was a stingingworm; I knew better than that, and wondered what they thought they were talking about. (Eastern Tent Caterpillars' fur will prickle and even raise a rash if it gets down your neck in hot weather, but so will your own hair.) As oak trees came back, so did the stingingworms. I miss the other casualties of the war on gyps, lament the decline of Tiger Swallowtails and Tuliptree Beauties, but life without the Hemileucas is...just...better.
Dr. Peigler was still teaching during the school term in which this post was written, and his paper introducing H. slosseri was printed in English with a Japanese summary at the end, which caused it to be digitized as a PDF:
Despite including "char.ja" at the end it was easy for me to read; the Unsatisfactory Toshiba likes PDF. For Peigler, at least, it may be good news that H. artemis was found in Tennessee.
Photos of artemis and nevadensis side by side show that the different-looking caterpillars grew into slightly different-looking adults. But not very different. You can find the photos online at
Tuskes, Collins, and Tuttle, whose Wild Silk Moths of North America is on sale for just under $500, reported that when artemis caterpillars were reared in California, they looked just like nevadensis. So maybe they're not a distinct species after all. A 2017 paper Peigler co-authored with Daniel Rubinoff concedes that, after DNA studies, the lumpers seem to be prevailing; the genus Hemileuca is now thought to have only six true North American species, with lots and lots of local variations.
"Diagnostic morphological traits are generally lacking" for the Hemileucas, complained B. Christian-Schmidt in a 2022 paper. DNA studies of this genus have not shed much more light on the question of species identity. They suggest that at least two of the variants that were first reported as distinct species, then declared too similar on the surface to be regarded even as sub-species, may actually be distinct species. When genetically distinct lifeforms look more like each other than genetically similar lifeforms, research is thoroughly confused. If you observe a female Hemileuca in a cage, the males who crawl around the cage trying to attract her attention won't all look alike. If she mates successfully (female Hemileucas mate once before laying eggs, and can mate one or two times more before laying more eggs), all of the hatchlings may be uniformly black or red, but by the fourth or fifth instar they won't all look exactly alike either. When even the consistent differences, like the yellow coloring of fifth-instar artemis caterpillars, may be food-dependent or weather-influenced, even entomologists are apt to give up and document the animal as "Hemileuca sp.," the old traditional shorthand for "I know there are different kinds of these animals but I don't know or care which one it was! It was a Hemileuca," or in ornithology "an Empidonax," or whatever else, "right? Now anyway, as I was saying..."
In fact, depending on the circumstances, Christian-Schmidt documented, the males attracted to a caged female won't all necessarily belong to her species. Artemis aren't closely related to the Great Lakes population that look similar to nevadensis and artemis, but they are mutually attracted, given opportunities. (Latifascia caterpillars can be yellow or yellow-striped. Or not..) Given a chance to produce offspring, an artemis-latifascia crossbreeding produced weak offspring that didn't live to maturity, a datum that might be useful toward encouraging local extinction. All the big silk moths have very limited time and are fairly desperate to mate; that some of the tests Christian-Schmidt reports showed males failing to approach a female of their own species suggests that something may have been wrong with the female. If hybridization can keep a female buck moth from producing viable offspring...that's not quite as good as her producing no offspring at all, but...
I like for these insect posts to feature modern, research-quality photos of living insects on the wing, or on the proleg in the case of caterpillars. I'm always disappointed when opening fifty or sixty pages yields only fair-use photos of sad little museum pieces. However, in the case of a species that has never been shown to serve any useful purpose, while at least annoying the daylights out of people and spoiling the pleasure of picking your own berries and cherries, maybe it's just as well. New pictures of artemis aren't likely to be collected because the latest research techniques don't support the status of artemis as a clearly separable species. Few people will miss the tiny distinctions among fifty or sixty color patterns on moths that, even when considered separate species, always were prone to hybridization as well as color variation. Not many more would miss the moths themselves. If the entire genus Hemileuca went extinct (without any other lifeforms being affected), among the minority of Americans who recognize moth species, some would be pleased.
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