Moths of
Britain and Europe
Emperor
Saturnia pavonia
LINNAEUS, 1758
Family -
SATURNIIDAE
subfamily -
SATURNIINAE
Tribe -
introduction
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habitats |
lifecycle |
adult behaviour
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Emperor, male,
Saturnia pavonia, Hampshire, England |
Introduction
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 Bombycidae.
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 wing tip.
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 Samia cynthia.
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 antennae.
Emperor, female,
Saturnia pavonia
Habitats
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.
Lifecycle
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.
The
greenish-white eggs are laid in batches of between 15-80, attached
to stems or twigs on the foodplants or other nearby plants.
The caterpillar
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 including Erica,
Crataegus,
Rubus, Vaccinium,
Salix, Betula,
Potentilla and
Prunus.
Pupation takes
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.
Emperor, female,
Saturnia pavonia
Adult behaviour
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 female.
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.
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