The holly blue (Celastrina argiolus) is able to hold its own in Essex because its foodplants (holly in
spring and ivy in late summer and autumn) remain plentiful, especially in gardens and parks. It was
particularly numerous in 1979. Population fluctuations are probably caused by unfavourable local
climatic conditions.
The graceful white admiral (Limenitis camilla), once widely distributed and often locally common
in Essex woods and spinneys, is one of the species which went into drastic decline in the eastern
counties in the 1950s and has so far not recovered. As stated earlier, it now seems to be largely
confined to a belt of protected woodland, in north-east Essex. The white admiral spread from its
southern and western strongholds in the early years of this century and its Essex population reached a
peak in the 1940s and early 1950s. There seems little doubt that it has suffered from hedgerow
destruction: in the past it used the 'corridors' of thick hedges between areas of woodland to recolonise
its main strongholds after periods of recession. Today the surviving colonies are denied such lines of
access.
The purple emperor (Apatura iris) was once locally common in the larger oak woods of north Essex
but by the turn of the century it vanished from these sites around Colchester and in the vale of
Dedham. The reasons are not clear as the habitats were not subjected to drastic change and there were
plenty of sallow bushes on which the females could lay their eggs. It is generally considered that the
eastern counties' purple emperors were severely affected by cold winters and cooler summers
compared with the warmer, more congenial climate to be found in the south of England where this fine,
big butterfly is still to be found in reasonable numbers in the larger oak and beech woods. The sighting
in 1983 of a purple emperor in the Epping Forest area has given rise to eager speculation that a colony
could have survived undetected over the years or that the species is attempting to recolonise the
county from sites to the west A male purple emperor was also found in a house at Wivenhoe in the
summer of 1982 and a search is being made of woodland in the area which might be supporting a relict
colony.
The big, tawny-coloured large tortoiseshell (Nymphalis polychloros) once included Essex among
its principal strongholds in the eastern counties. It is now one of Britain's rarest butterflies, threatened
with extinction. In Essex its gregarious caterpillars fed on elm leaves but the disappearance in the
1950s preceded the Dutch elm disease disaster so the causative factors must lie elsewhere. It is
believed that a series of late, cold springs, which affected pairing, and an abundance of parasitic wasps
which prey on large tortoiseshell larvae, tipped the scales against a species which is certainly on the
edge of its European range in the British Isles. Occasional records from coastal areas of eastern and
southern England would seem to support the theory that the large tortoiseshell could be dependent on
immigration from the Continent for re-establishent in Britain.
One of the depressing changes in the Essex butterfly fauna is the disappearance of the fritillary
butterflies. As was the case with the white admiral and the large tortoiseshell, this dramatic and
sudden collapse occurred in the 1950s when there were cool, wet summers and a series of late, cold
springs.
The pearl-bordered fritillary (Boloria euphrosyne) has, to all intents and purposes, vanished from
the Essex woods where it was once the commonest of its group. One reason for this population
collapse is the spread of bracken in woodland glades. This invasive growth chokes out the vital ground
flora including dog-violet which is the larval foodplant of this and most other fritillaries. Young
conifers are not inimical to the survival of pearl-bordered fritillary colonies but once the trees have
reached maximum growth they blot out light and frustrate the growth of flowering plants.
Although there have been recent sightings of the silver-washed fritillary (Argynnis paphia), high
brown fritillary (A. adippe) and dark-green fritillary (A. aglaja), these large, powerful butterflies
must, for the time being at least, be considered lost to our Essex woodlands. Colonies of the silver-
washed fritillary survive in woods on the Hertfordshire side of the Lea Valley so it is possible that
there could be some recolonisation of Essex woodland in due course. Much will depend on the
protection and maintenance of suitable deciduous woodland in Essex within flying range of the
butterflies.
One bright spot in the story of Essex butterflies is a recolonisation by the speckled wood (Pararge
aegeria) - a species which is actually spreading and increasing its range in Essex. Although common
in the 19th century it had virtually vanished from Essex woods and leafy lanes by 1900 and for more
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