Last week's moth article uncovered a researcher who was determined not to regard H. latifascia as a subspecies of either artemis or nevadensis, although most researchers do. This week we consider H. magnifica, sometimes considered a subspecies of hera but, perhaps because the moth is so eye-catching, Google still yields dozens of links (Yahoo says there are 17,600) to pages whose authors consider magnifica a separate species. Whatever. As we have seen by now, the Hemileucas seem to defy our idea of what a species is.
Photo by Stephanie N.
Magnifica live in Colorado and eat mostly sagebrush, sometimes snacking on plants in the genus Eriogonum. Their black and white wings usually span a little more than three inches. Like the smaller Hemileucas, they often fold up their wings and look smaller.
Photo b Matthew Priebe.
Some scientists think the "magnificent" wings of silk moths make it easier to flap unpredictably about, as they do when they suspect they're being attacked. Silk moths' wings are actually too big for maximum speed and maneuverability in flight, which is demonstrated by the sphinx moths, but they are good for flapping and fluttering in that indecisive way that can be so frustrating to a hungry bat.
Moths do much of their communication by scent, recognizing many scents humans seem unable to smell at all. We don't know what the female magnifica smells like though the chemicals humans have been able to identify in Hemileuca moth scents include some "fresh, clean" scents. A few spiders have the ability to mimic Hemileuca scents and lure male moths into their webs. Male magnifica seemed to be very vulnerable to this deception. That's just another way nature makes it hard for the silk moths to multiply.
Their life history was recorded by Stone, Swift, and Peiglrr in 1988.
Adult moths begin seeking a mate as soon as their wings have unfolded. Unlike some other Hemileucas, females usually perch in the lower branches of a sagebrush plant while they are "calling" with their scent, and instead of flying for a quarter-hour or half-hour after mating, they climb higher up the same plant to lay their eggs.
Mother moths lay eggs in clusters around a sagebrush twig. Magnifica often lives through most of two years, spending one winter dormant as an egg, the next winter dormant as a pupa. The first egg cluster contains 50 to 75 eggs; later egg clusters, 30 to 35 eggs each. They live five to seven days after emerging from the pupa. During this time the female moth produces a total of, on average, probably 175 to 200 eggs. A female needs to mate only once. Male moths continue trying to mate every day if they find a female every day, but seem unlikely to get the chance since each female may attract over a hundred males and will mate with only one of them.
They fly in the daytime and roost on sagebrush at night. Early in the morning they sit on the top of the sagebrush plant and bask in the morning sun.
Photo by Pete Thompson.
Eggs hatch in May in New Mexico, June in Colorado.
Caterpillars live in a cluster at first, gradually growing bigger and feeling a need to move out on their own. Their backs and sides are covered with bristles, each of which contains about as much venom as a bee sting. They use their bristles to maintain a close but breathable distance during the first three instars of their lives. Before molting into the fourth caterpillar skin, they become solitary animals. During the day they alternate between looking for the most succulent leaves at the top of the plant, in the sun, and the coolest places on the plant, in the shade. Their defensive behavior also changes as they mature; in the second and third instars they use the head-thrashing (and self-induced purging?) routine to confuse or disgust possible predators; by the fourth instar they drop to the ground and roll up with their bristles out to punish possible predators. They usually go through six instars, sometimes seven.
The base color is a dark blackish or purplish brown. White spots cover more of the skin surface as the caterpillars mature. The bristles form a double row of rosettes on the back with branching birstles on the sides and toward each endo of the caterpillar. As caterpillars and as moths magnifica look similar to hera but are half again as big. No clear photo of a magnifica caterpillar was available for this post. Stone et al. include a black-and-white photo showing that, while observation over their lifetime shows that these are dark brown caterpillars with black and yellow bristles and white speckles on their skin, they photograph as whitish caterpillars with dark patches on the skin and dark bristles.
Even more than other Hemileucas, magnifica seem vulnerable to fungus infections. If reared indoors they need a special full-spectrum "Gro-Light" and lots of air and space.
Robins have been known to eat magnifica caterpillars, but most of the predators holding this species in check are smaller than the caterpillars are. Tachinid flies and several kinds of small wasps parasitize the caterpillars, preventing them from maturing and reproducing.
By midsummer they are ready to pupate. They burrow an inch or two into the ground to shed the last caterpillar skin and spend the winter in the pupal form. They may spend two winters, and the summer in between, in pupation.
In support of the claim that magnifica is a distinct species, Stone, Swift, and Peigler say that subspecies usually occur in different places with intermediate forms found on the borders between their ranges, while hera and magnifica are distinguishable by size at all points of their ranges. The most obvious difference is size, and individuals reach the just-over-two-inches size or the just-over-three-inches size.
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