This family contains the moths commonly known as the emperors and giant silk moths, and is mainly tropical. Adult males have comb-like antennae enabling them to detect the scent of females at a great distance. There are around 1500 species world wide. Most of the adults in this family do not feed. They came by their family name because the concentric rings or eyespots of some species are said to resemble the rings of Saturn.
The Wild silk moth, Antheraea polyphemus, above is obviously a male. His pectinate antennae are large to enable him to detect the pheromones produced by the female, and his abdomen is relatively slim. In fact this moth may be the animal with the keenest sense of smell. He can detect a female if just one molecule of the peromone she releases when ready to mate lands on his antenna. In females although the antennae are still pectinate, they are not nearly so wide, and the abdomen in much rounder and fatter. Both males and females have four large eye spots; one on each wing, and both have similar colouration, although the shade can vary. The wingspan is 10 - 15 cm. These moths can be found from southern Canada down to Mexico, and are nocturnal. Adults mate on the same day they emerge from the cocoon as adults, and have no mouthpart so do not feed although they can live for up to a week.
The Atlas moth, Attacus atlas, above, has the largest wing area of any moth with a wing area of 400 sq. cm. and a wingspan of 25 - 30 cm. Each wing has a triangular or kite-shaped transparent area, the purpose of which is not yet known. Adults fly at night and rest amongst foliage during the day. Despite their large size they are difficult to find. In the wild it is found in South East Asia, although it is bred by collectors all over the world. Adults have a life span of just a week or two at the most, and during that time they cannot eat as they have no mouthparts. The females are larger than the males, and have relatively smaller, simpler and much less feathered antennae. Males are attracted to females by the pheromone the female emits from a gland at the end of her abdomen.
A female produces 200 - 300 eggs which are laid on the underside of a leaf and hatch in a week or two - the time to hatching depends on the surrounding temperature.
The caterpillars eat a wide variety of leaves including cinnamon, lime and other citrus, pomelo, guava, rambutan. Caterpillars reared in captivity will eat privet, willows, lilac, apple, plum, ash and cherry. Caterpillars feed for 5 - 7 weeks, and will grow to 11.5 cm long.
The pupal stage lasts around a month.
The female Emperor moth, Pavonia pavonia or Saturnia pavonia is above, and the male below. This moth is considered by some to have the best sense of smell of any animal, but see the Wild silk moth above. A male can smell the pheromone the female releases to attract him to mate from seven miles away! This moth is found throughout the Paleartctic, and is the only member of the Saturniidae family found in the U. K., it is normally seen in moorland and open country. The two specimens here are preserved, but in life the males have much brighter orange hindwings, the female colouring is similar, but less bright. Males fly by day especially on sunny days, and their flight is rapid. Females by night. The flight period is April and May. Male wingspan is 60 mm, and female 80 mm. Male forewing length is 27 - 32 mm, and female is 35 - 41 mm.
Eggs are laid in batches around the stems and twigs of the foodplant in May.
The caterpillar feeds on heather and bramble from May to August. It is green with yellow spots outlined with black, has bright orange spiracles (breathing holes) and short, black bristles, which is quite a colour combination, but it is perfectly camouflaged in the heather. I can attest to this having sat down next to one and happily eaten my lunch, drank my coffee, and not noticed it at all until I leaned over to put my things back into my rucksack, and dislodged it with my knee. The caterpillar grows up to 60 mm long. The caterpillar pupates on the foodplant, near the ground, in a cocoon, and the adults emerge the following spring.
Actias luna, the Luna moth, above, is found in North America, and has a wingspan of 114 mm, although 177 mm has been reported. In the north of their range they produce one generation a year, in the mid range (around the latitude of New York), two generations a year, and in the southern part of their range they manage three generations a year. The moth got its common name as the eyespots on its wings resemble the moon.
A female can lay 400 - 600 eggs in her lifetime, usually in batches of 4 - 7 at a time on the undersides of the leaves of the foodplant. The eggs hatch after ten days, and the caterpillars are green and grow up to 70 mm long. On hatching from the egg the caterpillars stay together until they have moulted two or three times, when the individuals will go their own way. Pupation is in a thin, silk cocoon spun among the leaves of the hostplant, which later fall to the ground. Adults emerge from the cocoon in the morning, usually males emerge a few days before females. Pumping up their wings to full size takes about two hours. Adults have no mouthparts, so do not feed and have a life span of just a week or so.
Males have larger antennae than females, and are strong fliers. Females release a male-attracting pheromone. Mating usually takes place after midnight, and the female starts laying eggs the next evening. The moths are greenish in colour, the preserved specimen above has faded.
The Spanish moon moth, Graellsia isabellae, above is found, as the name suggests, in Spain and also in France and Switzerland, from 500 m up to around 1800 m. The photograph above is of a female; males have large, feathery antennae, and tails to their hindwings. The wingspan is 65 - 100 mm.
It overwinters as a cocoon, and the adult emerges in late April or May, and is active mainly at dusk, flying until July. The female lays 100 - 150 eggs singly or in small batches on pine, the foodplant. The eggs hatch in one or two weeks and eat the pine needles. When fully grown the caterpillar is about 80 mm long. It pupates in a cocoon incorporating pine needles in leaf litter on the ground.
Above is the Comet moth, Argema mittrei. In the wild it is found in the rain forests of Madagascar. It is endangered in the wild, but has been successfully bred in captivity on a diet of eucalyptus and liquidamber. The male has a wingspan of around 20 cm and a tail length of 15 cm. In life the tails are bright red which has faded in this preserved specimen, and give the moth its common name. Males have longer tails than females.
The female lays 120 -170 eggs, which hatch after 20 days. On hatching the caterpillars feed for about two months, then they make a cocoon of silvery silk to pupate, which takes 5 - 6 months. The cocoon is like a sieve as it is full of holes. This is necessary to allow the rain from the daily downpours to drain out. The adult that hatches from the cocoon lives for just a few days, and in common with others in this family it does not feed. The adults are nocturnal. Mating takes place on the day the adult hatches from the cocoon. The female releases a pheromone to attract males. Like bumblebees the adults vibrate their wings to generate enough heat to allow them to fly. It is preyed on by geckos, birds, and lemurs.