4
seen Man Orchid Aceras anthropophorum on these southern slopes and Pyramidal Orchid
Anacamptis pyramidalis occurs here and elsewhere on the site.
The railway line defines the western edge of the area. At the southern end the chalk has
been colonised by birch but there are open clearings with very little vegetation where I
recently found a colony of Grayling butterflies. Walking through this area on the 31st
July I disturbed at least 9 specimens. Although single strays have been sighted in the
Thurrock area before this is the first confirmation of a colony of this butterfly in South
Essex. Grayling is very rare in the county with only small numbers surviving in the
Colchester district. This new population is clearly important and attempts to preserve it
should be made. A second notable find I made in this area on the same day is the Six-
belted Clearwing.
East of Mill Lane there is an area of grassland with some scrub, mostly grazed by horses.
The north and eastern parts of this area appear to be remnants of former grasslands that
have survived the various quarrying activities. As such they are unique examples of such
surviving calcicole grassland in South Essex. They have a good flora and an important
invertebrate fauna, including the Nationally Rare (RDB3) fly Zodion notatum apparently
with only four post 1960 sites in Britain and Myopa buccata, rare in Essex, both parasitic
on certain bees. There is also the Nationally Scarce wasp Odynerus melanocephalus
(Notable A), and the Nationally Rare and Scarce bees Andrena proxima (Rare- RDB3),
Andrena fulvago (Notable A), Andrena humilis (Notable B), Lasioglossum malachurum
(Notable B), Lasioglossum xanthopum (Notable B), Nomada fucata (Notable B), Nomada
pleurosticta (Notable A), and the Nationally Scarce spider Bianor aurocinctus (Notable
A).
The areas described here are clearly of county importance for invertebrates. It is now
too late to hope for more than the retention of some parts of the site but whether what
remains will be comparable is doubtful. Research (and common sense) dictate that the
fauna will severely suffer from fragmentation. All too often a similar scenario takes
place elsewhere in the country where the value of sites may be recognised by local
naturalists but the actual evidence that might help support these sites is only identified by
survey work done after threats appear, when the time span to identify most of the wildlife
value is too brief. Now that Local Plans incorporate SINC sites, Local Nature Reserves
and Areas of Local Nature Conservation Significance, the importance of having detailed
information before planning applications for development are made is essential and here
the Field Club has an important contribution to make today.
It seems worthwhile to include a full list of my records to date for the Mill Wood Pit area: