Caterpillars of the
World - Britain
Vapourer
Orgyia antiqua
LINNAEUS, 1758
Superfamily - NOCTUOIDEA
Family -
EREBIDAE
subfamily -
LYMANTRINAE
Tribe -
Orgyia antiqua
Strumpshaw Fen, Norfolk ©
Adrian Hoskins
Introduction
There are about 2700 species worldwide in the
subfamily
Lymantriinae,
the highest concentrations of species being found in South America
and the Afrotropical region. Madagascar alone accounts for no less
than 258 species. There are 32 species in Europe, of which 11 have
been recorded from the UK. Two of these are now extinct in Britain,
the Reed Tussock Laelia coenosa and the
Gypsy moth Lymantria dispar, although
the latter is slowly becoming re-established following introductions
and immigrations from continental Europe where it is still a common
species.
Moths in the Lymantriinae
are generally brown, greyish or white in colour, and most species
only bear weak patterns, typically in the form of dark suffused
greyish lines. Most species are nocturnal, although there are
several diurnal genera including Orgyia.
The genus
Orgyia comprises of between 65-70
species. They are represented in all temperate and tropical regions
of the world. There are 13 species in North America and 10 in
western Europe. All Orgyia species have
predominantly brown or greyish-brown males. The females are
wingless, or have very reduced wings, so cannot fly. Their bodies
are fat due to being heavily laden with eggs. Overall they have a
quite spidery appearance. Their inability to fly means that the
maintenance of genetic diversity is reliant on the ingress of flying
males, aided by the fact that a single female may mate with several
different males. Colonisation and expansion of range however occurs
only as a result of continuing short-distance dispersal by the
caterpillars, yet amazingly some species such as
antiqua are extremely widespread, and
inhabit a vast number of different habitats.
Orgyia antiqua is by far the commonest
and most widespread member of the genus, being found throughout most
temperate regions of the northern hemisphere.
Habitats
This species is ubiquitous in forests, parks,
farmland, gardens, scrubby grasslands and heaths, and can even be
found in city centres.
Lifecycle
The Vapourer forms its pupa within a silky cocoon
attached to tree trunks, fence posts, brick walls or virtually any
other rough textured vertical surface. The wingless females emerge
and spend their entire adult lives sitting on their cocoons. They
disseminate potent pheromones to attract males in from distances of
2km or more away. It is these pheromones or 'vapours' that give the
moth its English common name.
After mating the females lay all their eggs in a
single flat batch of about 200, on their cocoon. Upon hatching the
tiny larvae eat the upper part of their eggshells, and then rapidly
disperse in search of foodplants. They feed on a wide variety of
trees, bushes and woody plants.
The caterpillars
are blackish, and have tufts of stiff setae emerging from red or
orange tubercules on the back and sides. The first thoracic segment
bears a pair of long black forward-pointing tufts, and their is a
group of 4 dense tussocks of cream or buff coloured setae arising
vertically like little shaving brushes from the first 4 abdominal
segments. Female caterpillars grow to about twice the size of males.
Adult
Adult males fly on sunny days between late July
and mid-October. They have a rapid erratic flight, twisting and
turning as if in a demented state, and soaring high above trees. In
Leicester the moths have even been observed from the 13th floor of a
city centre building. The apparently crazy flight pattern is quite
deliberate - the rapid and random changes of direction make it much
easier for the moths 'scent radar' to track and home in on the
pheromone trail of the females.
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