The largest moth seen north of Mexico is the Black Witch, Ascalapha odorata, a member of the noctuid family. The moth is quite distinctive, with a wingspan sometimes exceeding 7 inches. It is not actually black, but a variegated dark brown marked with zigzag black lines and faint touches of pink and lavender.
A number nine or paisley shape on each forewing, dark green outlined in reddish brown or orange, is the distinguishing mark of the Black Witch. The females also have a white stripe midway along each wing and are slightly paler than the males. Both genders have a bluish iridescence to the scales that cover their wings.
Like many moths (though not all), the Black Witch only flies at night. It may hang under eaves or cars to sleep through a day or two in its migration. In spite of its threatening appearance, the Black Witch can only suck up nourishment through a straw-like proboscis that is coiled on its head in flight. The odor of soft overripe fruit attracts it, and so does the alcohol that forms when fruit decays. Food must be a pulpy liquid for the moth to be able to eat it.
The beginning of the rainy season in Mexico, in spring, triggers the first northward migration, and overlapping generations of the moths move north through the warm months. They are common in the American desert southwest, but stragglers have been seen in New Jersey and even Alaska. They are also known in Hawaii, although they are not native there. They breed year around where conditions permit. In fall, they pull back southward.
The larva feed on legumes like acacia, mesquite and locust, and Candle Bush, Woman's Tongue, and Texas Ebony. They are large, nearly 3 inches long, and pale gray tinged with brown. They have stripes and spots that help them blend in with the bark of the plants that are their food.
The adult moth, the imago, is quite bat-like in form and flight, inspiring many superstitious beliefs throughout its range. In general it is an omen of bad luck. If it flies into a house in Mexico where someone is ill, that person will surely die. This belief has been modified in the Rio Grande Valley of Texas so that the moth must fly in and visit all four corners of the house for the spell to take effect.
In some Caribbean populations, the Sorciere Noire is believed to be an actual witch in disguise, and to see it means someone has cast an evil spell on you. In Jamaica it is called a Duppy Bat, and believed to be a lost soul. These superstitions are easy to smile at in daylight, but when a huge silent creature is drawn to your reading light at midnight, then you may well believe.
In parts of the Bahamas, folklore calls them Moneybats, and tells that they bring prosperity. In Hawaii, where the huge moths are only occasionally seen, some people claim that the Black Witch is a dead friend come to say goodbye.
The novel Silence of the Lambs uses the pupa of the Black Witch moth as a prop. However, in the film version, its place is taken by the less subtly unsettling Deaths-head Hawkmoth.
The Black Witch moth is a necessary part of the ecology, and as lovely as any butterfly. Because it does not suit human ideas of how an insect should behave, it seems frightening. It is too large for a moth, and too dark. Its silent movement is associated for us with the ancient terrors of night.