122 Heath Fritillary in Essex: a review of its status and a report of its second generation
1935, surviving for some time before its extinction in the 1960s. Nowadays, the on-going management
work also includes the widening of rides to encourage the butterfly to migrate to new areas, and also
the planting of Hornbeam saplings in the coppice plots to ensure a more dense woodland growth in
the future. The council receives financial assistance from EN to aid with the coppicing work: it is
essential that newly-felled areas of trees arc close to - or preferably immediately adjacent to - an
established breeding population, as they are generally very sedentary insects and unable to colonise
new sites if it means negotiating shaded woodland.
The most recent location where the Heath Fritillary has been introduced is at Pound Wood at Daws
Heath, close to the colony at Hadleigh Great Wood. As with Thrift Wood, this is also an EWT
Reserve; the butterflies were taken from both Hockley Woods and Thrift Wood in 1998. Unfortunately,
the creation of a potentially suitable environment for the butterflies does not appear to have been a
priority so far, as only a very insufficient clearing was made in late 1999. In addition, part of the
flight area is under a 'wayleave' and requires a particular management regime to be undertaken by
the electricity company, the timing of which is not always best suited to the butterfly's requirements.
Only a very small number of Heath Fritillaries were observed in 1999, and unless some more drastic
and concerted action is taken at Pound Wood, the species is likely to die out.
Another aspect of the wider biology of the species involves the specific requirements of the larval
food plant Common Cow-wheat. This annual plant occurs in Essex principally in ancient deciduous
woodlands where it is largely confined to acid soils and is semi-parasitic on the roots of certain other
plants such as grasses. It is very scarce or absent in the densely shaded areas under the woodland
canopy, but often becomes abundant for a year or two after coppicing is instigated. The egg batches
are laid on or near the foodplant in very warm and sunny conditions. Such conditions will usually
last only a season or so due to the re-growth of vegetation, which leads to the micro-climate being
cool and shaded, and avoided by gravid females. All the surviving colonies of Heath Fritillaries in
south-east England occur in coppice or newly-felled woodland. The presence of Wood Ants Formica
rufa may be beneficial to the butterfly as they are known to transport cow-wheat seeds around their
foraging areas - this advantage is likely to outweigh any potential Wood Ant predation of the fritillary
larvae, which is thought to be minimal.
Essex Biodiversity Action Plan for the Heath Fritillary
The Heath Fritillary has long been one of the rarest resident butterflies in Britain, and it was possibly
our most threatened butterfly around twenty to thirty years ago. However, detailed studies of its
ecology and particular habitat requirements now means that in its Essex woodland environs it can be
specifically catered for, knowing that basic woodland management (in the form of coppicing) and an
annual supply of the larval foodplant are the prerequisites for a colony to maintain itself over the
years. Due to the Heath Fritillary's extremely restricted range in Essex - where all the colonies are
introductions - and elsewhere in England, the insect is listed as vulnerable on the GB Red List (RDB
2), and is protected under Schedule 5 of the Wildlife & Countryside Act 1981. It is also listed as a
Priority Species in the UK Biodiversity Action Plan due to its very high risk status and susceptibility
to local extinctions.
At the present time, this species is thankfully not in decline. However, conservationists need to be
aware that the situation could change very rapidly and the butterfly may die out at a site where only
three or four years earlier it was abundant. The main factors that could affect the future existence of
Heath Fritillary in Essex include the loss of suitable woodlands, the isolation and fragmentation of
their ideal habitats, and also the degradation of suitable areas by the cessation of sympathetic habitat
Essex Naturalist (New Series) 17 (2000)