Seasoned BugFans rejoice! A moth that you can actually see with your naked eye! The Azalea Sphinx is a member of the Sphinx family, Sphingidae—Sphinx moths have appeared in these pages before, in the person of the White-lined, the Pandorus, the Laurel/Fawn, the Waved, the Walnut, the Five-lined, and the Hog/Virginia creeper sphinxes, as well as the Cinnamon and Bumblebee/snowberry Clearwings. Sphinx caterpillars are called hornworms for obvious reasons, though in some species, the horn is lost or reduced in their last instar.
Sphinx Moth Caterpillars
Sphinx moth caterpillars are frequently associated with one, or a small group of host plants, for which they are often named (tobacco and tomato hornworms, big poplar, wild cherry, huckleberry, catalpa sphinx, etc.). Some are pests of agricultural or horticultural plantings, and they may have different names than their adults (when it grows up, a tomato hornworm becomes a Five-lined sphinx). The caterpillars are responsible for the name Sphinx—when alarmed, they raise the front half of their body, retract their head like a turtle and pose like an upside-down Egyptian sphinx (OK—so entomologists are an imaginative bunch). Adults may be called Hawk moths (especially in England) and hummingbird moths (for their feeding style).
These are big moths—some tropical species may have a seven inch wingspread. North American sphinx moths, some of which may have four inch wingspreads, represent about one-tenth of the approximately 1,500 species worldwide. They have chunky, scaly, spindle-shaped bodies and long, roughly triangular wings; the wings of some species are decorated with color-blocks. Many adults have strikingly-colored hind wings or abdomens that are concealed when they are at rest but are flashed in flight to startle predators. Sphinx moths are terrific flyers; their rapid wing beats can carry them up to 12 mph, and they can also hover.
In spite of the fact that adults communicate using airborne chemicals (pheromones) they don’t have especially feathery antennae (she calls to him using pheromones, and in some species, he responds with pheromones of his own when he gets close). Although many are night-flyers, they have no hearing organs/bat detectors.
The caterpillars can be sizable, too. Some are cryptically colored, but others have a line of big, attention-getting spots along their sides. The caterpillars of closely-related species can be hard to tell apart because they may come in different color phases, but apparently, the size, shape and color of the horn can be diagnostic. Caterpillars turn darker as they approach pupation, and they overwinter as pupae.
Interesting stuff about Sphinx moths:
- Many sphinx caterpillars nosh on toxic leaves. Animals that ingest poisons either sequester them, eliminate them, or live with them. Although some species are pretty impervious to high toxin concentrations, they also excrete them quickly; other species neutralize harmful substances like nicotine before eliminating them. In the “If You’ve Got It, Flaunt It” department, caterpillars regurgitate the noxious contents of their foreguts on aspiring predators and parasites (although this one was unsuccessful and is parasitized by wasp larvae). They do not, however, pass any toxicity along to their adult phase.
- Sphinx moths not only hover, they can move side-to-side (side-slipping” or “swing-hovering), which might help them avoid ambushers lurking in the blossoms.
- Sphinx moths must raise the temperature inside their thorax to about 96 degrees F in order to fly—this they do by quivering the wing muscles, causing the wings to vibrate. The warm-up takes longer in cooler temperatures, but because of their ability to warm up, they can fly in cool/nighttime temperatures. They also bask.
- Adults of a few species don’t eat (they depend on energy socked away during their larval stage), but most have a proboscis that is long enough to uncurl into a tubular flower and harvest its nectar (incidentally, pollinating it). Like their caterpillars, adults may be associated with specific flowers and be their exclusive pollinators.
- Darwin once predicted the existence of a hitherto-unknown animal species, based on the size and shape of a tropical orchid. “[A. sesquipetale has] nectaries 11 and a half inches long, with only the lower inch and a half filled with very sweet nectar […] it is, however, surprising, that any insect should be able to reach the nectar: our English sphinxes have probosces as long as their bodies, but in Madagascar there must be moths with probosces capable of extension to a length of between 10 and 12 inches!” When the pollinator—a sphinx moth—was ultimately found, its subspecies name (praedicta, the predicted one, reflected his observation.
- Not all sphinx moths feed on plant nectar (the Faint of Heart should turn away right about now); one species robs honeybees, but about 100 species, mostly in Southeast Asia, sip “eye secretions”. From the Medical and Veterinary Entomology, by Mullen and Durden, we learn that “It feeds while hovering about the eyes of horses, mules, and humans. It also has been observed inserting its proboscis between the lips and into the nostrils of humans to feed on saliva and nasal secretions. The latter has been described as causing a tickling sensation. Only mild discomfort is experienced when they feed on eyes.” And yes, there is a vocabulary word for that–lachryphagous. (OK, you can turn back now.)
The Azalea Sphinx (Darapsa choerilus) (formerly Darapsa pholus) is one of three species in its genus in the Nearctic ecozone and is found in deciduous woodlands and edges from the Great Plains, east. Wagner, in Caterpillars of Eastern North America, says that the three Darapsas (the Azalea, the Hydrangea, and the Virginia creeper sphinx) “usually can be identified by their foodplant associations.” Both the adult Azalea sphinx and its larva are similar to the related Hog sphinx, but the Azalea sphinx’s horn is straighter and bluer.
Because of its more-catholic-than-usual diet, the Azalea sphinx could also be called the Blueberry, Sour gum, or Viburnum sphinx, (multiple sources continued “and other host plant families” but didn’t name them). Adults nectar on a variety of flowers, tubular and not, that are open during the evening and at night, like honeysuckle, bladder campion, Eupatorium, Spiraea and, apparently, milkweed.
There are probably two generations each summer here in Wisconsin (possibly eight per year along the Gulf Coast). The young are solitary feeders that snug up against the midrib of the leaf they’re eating when at rest. When they’re ready to pupate, they use silk to fasten a few leaves together loosely on the ground.
Gratuitous caterpillar picture that the BugLady wishes she had taken: http://bugguide.net/node/view/996714.