Hemileuca Griffini

Hemileuca griffini, Griffin's Sheep Moth (or Griffin's Buck Moth), is usually found alive in Arizona and Utah. Often mistaken for H. hera, it's smaller and has a typically different pattern of wing markings. The markings are vivid, attractive, and simple to draw--all black and white--so this moth is a popular subject for artwork, including tattoos. Live moths are offered for sale online; like all silk moths, they don't live long and need to be shipped as pupae or, sometimes, as eggs.

The adult moth doesn't have a mouth or a digestive system; it lives entirely on stored fat, and doesn't store much. The caterpillar eats only the desert plants known as Black Brush and Canadian Fleabane. So far, no caged Hemileuca griffini is known to have escaped from captivity and become an invasive nuisance, but all of the Hemileucas are nuisances in the places where they are native. 

It would be useful if informational web sites would give the typical size of a moth in objective measurements rather than pictures. One never knows whose hand is being used as a measurement in photos like this. One could more usefully say that each forewing is a little over an inch long, the female's typically two or three millimeters longer than the male's. It's still a good-sized moth, but among the "giant" silk moths it's one of the smallest.

Named by Paul M. Tuskes after Bruce Griffin, who collected the first specimens Tuskes studied, H. griffini was recognized as a separate species only as lately as 1978. Before that it was probably seen as a straying, malnourished H. hera.  It flies in the daytime, usually  in September and October, sometimes in August.. Tuskes described its differences from H. chinatiensis, which it resembles even more than hera, in excruciating detail in a paper available online: 

https://images.peabody.yale.edu/lepsoc/jls/1970s/1978/1978-32(2)97-Tuskes.pdf

For experts like Tuskes, the interesting thing about H. griffini was that its body structure seemed to link the different shapes of H. hera with the other Hemileucas. At the time some were classifying hera as a separate genus. Not only is hera bigger than griffini and chinatiensis; its posterior end has a different shape. Nevertheless, at the "What kind of insect is this?" sites, people who consider only the wing coloring are always confusing griffini with hera. \

 

Adult moths mate, lay eggs on their host plants, and die. The eggs hatch in April. The caterpillars live in family groups. Immune to each other's bristles and venom, they clump together for shade on hot days and insulation on chilly nights. They can grow up to two inches long. Whether they can live on rose, serviceberry, or fruit tree leaves, or whether eating those causes them to develop into a different color or even shape, online sources don't say. They will infest fruit trees, though, if they can. They tend to develop the flatter rosette type of bristles on the back, which allows them to deliver a nastier sting than some of the larger Hemileuca caterpillars. 

They come in different shades of brown and gray, but usually show distinct lengthwise stripes of lighter and darker color, and the bristles on older caterpillars are greenish. This color scheme gives them some resemblance to mossy twigs found in the high and dry country. 

For silk moths the Hemileucas produce remarkably little silk. When the caterpillars are ready to pupate they crawl down into the sandy soil until they feel covered, and lie still for the rest of the summer. By late August or September they have become moths, though as they crawl up out of their burrows they still look a bit wormlike. It takes a few hours for the wings to expand to their full size.  Males follow an odor humans don't smell to find females; one male then has the chance to mate, while others sit around telling themselves "Better luck next time." Females then fly out to consider different food plants and select those likely to offer the best nutrition for the next generation. 

Though nobody ever has actually liked a stingingworm, nor ever will, the moths are rare enough that some people manage to feel protective of them. It seems obvious that nature intended them to be rare; some people claim a strong personal preference, as distinct from a philosophical belief, that they should not become extinct. 

Most moths mate facing away from each other, cautious not to damage their wings, but the silk moths fly less than other moths and sometimes embrace, enfolding the smaller partner in the larger one's wings. Hemileucas often embrace face to face. They spend time snuggling, too, before and after mating, though usually less than an hour. Scent is a primary means of communication for moths and they probably spend time sensing each other's desires and satisfaction through their scents. 

They can afford to risk bumping wings better than most moths can: they'll fly less in any case. All of the Hemileucas are so much easier to like as moths than as caterpillars that it seems unfair that they spend months being caterpillars and only days being moths.