Hemileuca Chinatiensis

Though its claim to be a distinct species is now being disputed, Hemileuca chinatiensis, the Chinati Sheep Moth, has been one of the better studied Hemileucas, with dozens of search engine hits. Named for the Chinati Mountain in Texas, they're found throughout the Southwest. In Texas they're found only in the western part of the State. 

When the Hemileucas fly in the daytime, as they often do, they're often mistaken for butterflies.

Genetically, scientists now think there are only a few distinct species of Hemileuca, a genus of moths whose looks can vary widely depending on several hereditary and environmental factors. Litter mates can look more different from one another than individuals who have enough different DNA to be regarded as different species. Newly hatched Hemileuca caterpillars are gregarious, and while all the caterpillars in a cluster may look alike to humans, they may also include three different color patterns.

Hemileuca conwayae, which was listed as a separate species in the twentieth century, was soon recognized as not even a consistent variation of H. chinatiensis, just another variation within this species' range. Around Conway, Texas, the moths showed consistently darker wings (wider bands of black around smaller spots of white) and more black on the body. This question was settled before the Internet and, although information about conwayae was printed and may still be in some university library somewhere, documents about conwayae as a separate species don't seem to have been posted to the Internet. Photos and descriptions of chinatiensis and conwayae as distinct species have been preserved in https://repository.arizona.edu/bitstream/handle/10150/609134/dp_10_01-013-030.pdf?sequence=1 .Nevertheless, the melanism of conwayae proved to be caused by diet.

H. chinatiensis, however, seems to be keeping its status as a separate species. The species Tuskes recognizes, in his gorgeous $500 book, as distinct enough to be listed separately are burnsi, chinatiensis, eglanterina, electra, maia, and tricolor. However, confusion continues to rage. Some science sites list schemes of classification that do and don't mention chinatiensis.

Hemileuca chinatiensis typically have buff to orange bodies and gray-and-white to black-and-white wings. They often fold their wings, as smaller moths do, and look smaller than they are. The wings unfold to more than two inches across, sometimes almost three inches, 5 to 7 cm. Females in some Hemileuca species are consistently larger than males but this difference is less reliable for H. chinatiensis. Another way to tell males from females is their flight patterns. The big silk moths don't have energy to waste, so they usually fly only for a good reason. Males are most likely to fly toward the scent of a female, moving quickly, shifting directions as they follow the scent upwind. Females most often fly when looking for a place to lay eggs; they seem to need a bit of exercise in between getting laid and laying, even if already near a suitable plant, and their flight tends to be slower and steadier. Males usually fly earlier in the day than females. 

Adult moths also tend to curl up their flexible bodies, like caterpillars. 

Going by looks, in the past, scientists had named more than fifty species of Hemileuca, some of which were quickly recognized as sub-species or variant forms of the same general kind of moth.

Silk moths have short adult lives and try to make seconds count. When a female sheds her pupal skin and spreads her wings, it can look as if she is just sitting still, minding her own business, until she is surrounded by males. In fact, while pumping blood into her wings she is actively pumping out the distinctive scent of her type of Hemileuca. How much a moth is able to think and choose is a matter of speculation, but voluntary movement is visible; some refer to this pulsating and pumping process as "calling." Males usually follow the scent of a female of their own physical type, but often types that have been seen as different species hybridize. Really different species usually avoid hybridizing when possible, and produce sterile or otherwise physically disadvantaged offspring if they do hybridize. The willingness of most Hemileucas to consider mates who look very different from them, and the fact that offspring who show an in-between look can be normal healthy moths who can produce little stingingworms of their own, kept scientists debating about which Hemileucas belong to different species until DNA studies became possible. 

Repulsive though they are to all other lifeforms, the Hemileucas seem to tolerate or even like each other. During their first few weeks of life the young caterpillars stay together in family groups, showing complete immunity to the venomous spines as they crawl over each other (apparently to regulate body temperature). Older caterpillars ignore or positively avoid each other when each one needs to find its own food plant, but as moths Hemileucas tend to cuddle. They can mate back to back, as most moths do, protecting their wings, and their flexible bodies also allow mating while perched side to side, but they are often found mating face to face around a twig. With their wings unfolded, held up over their backs like butterflies' wings, this pair looks like one large moth. 

The things people hate about the Hemileucas do not include racism. H. chinatiensis don't normally meet H. eglanterina but, when they do meet, they consider each other as potential mates. Some authorities list chinatiensis as a subspecies of eglanterina for this reason.

Diet is a factor in the different looks Hemileucas develop as the half-grown caterpillars leave the clusters in which broods of baby caterpillars live, find their own way in the world, and usually find different food plants available. They can, for example, eat Forestiera species. Forestiera, sometimes called "fake" or "American" olive, can look remarkably similar to English privet (Ligustrum), and one way to know which you have is that stingingworms live on Forestiera and don't even snack on privet. 

This New Mexico Forestiera, with bigger sloppier-looking leaves, is a favorite food plant for Hemileuca chinatiensis. They can also eat condalia, ephedra, krameria, mahonia, and mimosa. But their very favorite food is said to be sumac--the flowers more than the leaves.. 

Thus one of the few caterpillars likely to raise a rash on your hand is often found on one of the few plants likely to raise a rash on your hand. A person who stumbled into both would really be sorry. (Actually, the urushiol in the Rhus plant genus is likely to do more damage to more people than the caterpillars are...but it's best to avoid contact with either.) 

Poison ivy and poison oak are seldom eaten by insects but sumac is a favorite with many big silk moths. If you want to see North America's biggest non-tropical caterpillars, plant sumac. It hosts Cecropias, Eacles, Citheronias, and other big but harmless caterpillars, and then the Hemileucas, which aren't big compared with lunas and cecropias, and aren't harmless, either. 

Different food plants promote different looks as the caterpillars mature. The dark coloration of chinatiensis may be produced by the same phytochemicals that produce the coloring of a different silk moth, Agapema dyari, sometimes found sharing host plants with H. chinatiensis.

Few other lifeforms would ever try to eat a stingingworm. Even the adult moth's colors warn that it would be toxic to warm-blooded animals if ingested. Nevertheless, though overprotected against mice and birds, stingingworms are sometimes attacked by cold-blooded animals such as this little beetle, magnified for research purposes.

They are even more vulnerable to tiny braconids and tachinids. They can also suffer from virus and bacterial infections, microscopic parasite infestations, and, in wet weather, from fungus infections. A rule for rearing Hemileuca in cages is that the animals must be kept dry. The genus seems to have originated in the southwestern desert. Though the moths have spread northward and eastward, and some forms tolerate cold or rainy weather, the caterpillars may survive being stepped on more easily than they can survive a wet spring.

Braconids are usually described as a sort of miniature wasp or miniature fly. They lay their eggs on the skins of small caterpillars that will grow into large caterpillars. The braconid larvae burrow in through the caterpillar's skin, probably releasing anesthetic chemicals as they go, and proceed to eat the caterpillar's middle and back ends. The caterpillar may or may not know something is wrong--a few of the more conscious species, like the tent caterpillars, do squirm and try to shake off the egg-laying braconids--but it can't do anything about it. Sometimes a caterpillar's final molt discloses a skin festooned with little white braconid cocoons. This is optimal for the braconids; the caterpillar won't live long enough to pupate but the braconids don't need for it to.

Moths usually fly between September and November. Individual moths fly for only a small part of their season. Couples who meet usually stay together for several minutes, apparently admiring each other before and after reproducing. After separating, if they get a chance they may mate again with other moths. A female usually lays three clumps of eggs, and a male will try to fertilize three broods of eggs if he has a chance, which he seldom does. Both males and females are much more likely to pass on DNA on the first try.

Caterpillars usually crawl in late spring and early summer. 

They pupate in late summer and don't make much effort to hide while pupating. 

I found the caterpillar and pupa pictures above only at https://joias-da-natureza.blogspot.com/2022/01/hemileuca-chinatiensis-tinkham-1943.html ; they may be the blogger's original work. (It's generally a mistake to try to read Portuguese as if it were Spanish but scientific terms are meant to be a sort of international dialect.)  This blog also contained photographic evidence that the moths cuddle--one apparently putting its head under the other's wing, not mating, just snogging.

Another Blogspot blog, with no distinctive photos of this species, mentions that rearing this species in captivity in Europe was difficult because, for one thing, these desert moths' process of maturation in the pupa is tied to humidity rather than light. Their growth spurts occur during their natural environment's rainy season. In swampy Belgium, the blogger's moths started flying in June and July rather than September. http://silkmothsandmore.blogspot.com/ is a very flashy blog that doesn't link to individual posts; whenever the blogger has posted about enough other moths person has reared, the post for Hemileuca chinatiensis may or may not be easy to find.