Saturniidae

Saturniidae, commonly known as saturniids, is a family of Lepidoptera with an estimated 2,300 described species. The family contains some of the largest species of moths in the world. Notable members include the emperor moths, royal moths, and giant silk moths. Adults are characterized by large, lobed wings, heavy bodies covered in hair-like scales, and reduced mouthparts. They lack a frenulum, but the hindwings overlap the forewings to produce the effect of an unbroken wing surface. Saturniids are sometimes brightly colored and often have translucent eyespots or 'windows' on their wings. Sexual dimorphism varies by species, but males can generally be distinguished by their larger, broader antennae. Most adults possess wingspans between 1-6 in (2.5–15 cm), but some tropical species such as the Atlas moth (Attacus atlas) may have wingspans up to 12 in (30 cm). Together with certain Noctuidae, Saturniidae contains the largest Lepidoptera and some of the largest insects alive today. The majority of saturniid species occur in wooded tropical or subtropical regions, with the greatest diversity in the New World tropics and Mexico, though they are found all over the world. About 12 described species live in Europe, one of which, the emperor moth, occurs in the British Isles, and 68 described species live in North America, 42 of which reside north of Mexico and Southern California. Some saturniids are strictly univoltine, producing only one generation a year, whereas others are multivoltine, producing more than one brood a year. Spring and summer broods hatch in a matter of weeks; autumn broods enter a state known as diapause and emerge the following spring. How the pupae know when to hatch early or hibernate is not yet fully understood, though research suggests day length during the fifth larval instar plays a major role, as well as cooling temperatures. Longer days may prompt pupae to develop early, while shorter days result in pupal diapause. The number of broods is flexible, and a single female may produce both fast-developing and slow-developing individuals, or they may produce different numbers of broods in different years or parts of the range. In some species – e.g. the Luna moth (Actias luna) or Callosamia securifera (both Saturniinae) –, spring and summer broods look different, with different genes activated by environmental conditions. Depending on the moth, a single female may lay up to 200 eggs on a chosen host plant. Others are laid singly or in small groups. They are round, slightly flattened, smooth and translucent or whitish. Saturniid caterpillars are large (50 to 100 mm in the final instar), stout, and cylindrical. Most have tubercules that are often also spiny or hairy. Many are cryptic in coloration, with countershading or disruptive coloration to reduce detection, but some are more colorful. Some have urticating hairs. A few species have been noted to produce clicking sounds with the larval mandibles when disturbed. Examples: Luna moth (Actias luna) and Polyphemus moth (Antheraea polyphemus). The clicks may serve as aposematic warning signals to a regurgitation defense. Most are solitary feeders, but some are gregarious. The Hemileucinae are gregarious when young and have stinging hairs, those of Lonomia containing a poison which may kill a human. Arsenura armida is another well-known example, and are infamous for their large conspicuous masses during the day. Their coloration is not cryptic, instead exhibiting aposematism. The other caterpillars in this size range are almost universally Sphingidae, which are seldom hairy and tend to have diagonal stripes on their sides. Many Sphingidae caterpillars bear a single curved horn on their hind end. These are actually not dangerous, but large-haired caterpillars should generally not be touched except by experts.