Moths of Britain and
Superfamily - BOMBYCOIDEA
Family - SATURNIIDAE
The Emperor moth is the only member of the Saturniidae found in
Britain. The family is named after the ringed planet Saturn, on
account of the large ringed spots that are found on the wings of
most species. The Saturniidae are commonly known as wild silkmoths
because most species construct elaborate silk cocoons. Several
tropical species including Antheraea mylitta
are commonly bred in captivity and used to produce commercial silk.
The well known "silkworm moth" Bombyx mori
is unrelated, belonging to a different family - the
The 1500 species of
Saturniidae are distributed mainly throughout the tropical regions
of the world, and include the spectacular tailed
Actias and Argema
Moon moths, and Attacus atlas - the
Giant Atlas moth, which is the largest species of moth in the world
( in terms of wing area ), measuring up to 30 cms from wing tip to
In Europe there are
5 Saturnia species including the
Emperor Saturnia pavonia, and the
similar but much larger Great Peacock moth
Saturnia pyri. There are also several members from other
genera including the orange winged Tau Emperor
Aglia tau, the Autumn Emperor
Perisomena caecigena, and the Spanish Moon moth
Graellsia isabellae. Additionally there
are 3 introduced species - Antheraea yamamai,
Antheraea pernyi and
The male and female
of Saturnia pavonia are marked
identically, but the male is smaller, has more brownish-pink
forewings and chestnut brown hindwings, and has strongly pectinate
This is primarily a heathland and moorland
species, but can be found also in woodlands and scrubby grasslands
in certain areas. In Britain it is a lowland species, but it can be
found at altitudes as high as 1800m in the Alps.
Saturnia pavonia flies from March to
July depending on locality. In southern and western Britain it
usually emerges in late April, while in Scotland it typically
emerges in mid-late May.
eggs are laid in batches of between 15-80, attached to stems or
twigs on the foodplants or other nearby plants.
when young feeds communally, and is black with orange markings, and
covered in short stiff white or black spines which emerge from
tubercles on its back and sides. When older it lives solitarily and
is bright green, with narrow vertical black bands between the body
segments, and possesses prominent yellow tubercles from which emerge
stiff hairs. It feeds primarily on heather (
Calluna ) but will also feed on a wide range of other plants
Potentilla and Prunus.
place in a pear-shaped cocoon made of coarse brown silk. The cocoon
is a most fascinating object with a beautifully constructed
"lobster-pot" trap door which enables the emerging moth to escape,
but prevents predatory insects or spiders from entering.
Saturnia pavonia, Hampshire ©
Female Emperor moths
possess an organ at the tip of their abdomen from which they
disseminate pheromones to attract the day-flying males. A single
freshly emerged female can attract as many as 70 males, which can
detect the pheromones from distances of a kilometre or more away,
using their strongly pectinated antennae as "radar" to home in on the
The females are
heavily laden with eggs so are unable to fly very far, and after
mating lay most of their eggs very near the spot where they emerge.
After laying 100 or so eggs they have lightened their load
sufficiently to enable them to fly, but unlike the males they fly by
night. It takes them about 2-3 days to complete egg laying.
Neither sex has a proboscis, so the moths
are unable to feed, and only live until their body fats are exhausted
- i.e. about 4 or 5 days.