The Distribution Maps
by A. M. Emmet
At a meeting held on 19 November 1981 and attended by representatives of the Essex Field Club,
the Essex Naturalists' Trust and the three museums which maintain records of Lepidoptera
(Southend, Colchester and the Passmore Edwards) it was decided to produce a new county list of the
macrolepidoptera including a distribution map for each species prepared on a 10km square basis. As
an important source would be the Biological Records Centre, Monks Wood, whose records are
divided into those made prior to 1960 and those from 1960 onwards, it was decided to adopt these two
categories. However, the meeting felt that a division of the post-1960 records was desirable and
agreed to differentiate between those made from 1960-69 and those made from 1970 onwards. These
three classes of record are therefore shown on the maps, using the symbols listed below. I volunteered
to make up the maps and the purpose of this section is to explain the source of the records.
The starting point was the Guide, but this was a county list written with a different aim, its purpose
being to show the present status of Essex macrolepidoptera Historic research was of secondary
importance and species not recorded since 1925 were relegated to an appendix. For common species
a generalised summary sufficed without the inclusion of any record which could be plotted on a map.
Contributors were, in fact, instructed that records were not required for a long list of species regarded
as widespread and common. Details were given of local species but sometimes without exact dating
A card index of the records on which the Guide's summaries were based is lodged at the Colchester
Museum and this to some extent supplemented the Guide. Nevertheless, the maps at this stage were
very meagre because the Guide simply had not set out to give the degree of detail required for map-
making.
The next source was the Biological Records Centre. Most lepidopterists used to send in their
records annually until the macrolepidoptera recording scheme was discontinued in 1982. These are
registered on a 10km square basis, are stored in a data bank and are available on request The BRC
cannot in any way be held responsible for the accuracy of the information submitted. It will, however,
supply the source of any particular record and the onus is then on the user to assess its validity; in our
case a number could not be substantiated and were therefore rejected. The BRC was the main source
of records in the two earlier categories; their post-1960 records were treated as belonging to the 1960-
69 category unless there was evidence that they were made later.
Modern farming techniques pose a threat to insect populations. In order to give early warning of
any sudden decline, the Rothamsted Research Station run a network of traps distributed over Britain
with usually three or four operating in Essex. The statistics so obtained have been made available to us
by Rothamsted. The accuracy of determination is now very high but not 100% reliable and, as the
specimens are not kept, checking is impossible. For this reason, a few unlikely records have been
rejected
A comprehensive search for records was made in journals and text-books and was undertaken in
greater depth than was deemed necessary for the compilation of the Guide. Several important early
lists not previously used were consulted; these included Doubleday, E, (1836), Burnell(1837), Gaze
(1842) and Whittle (1899a). The records listed by Harwood (1903) in the Victoria County History
were as far as possible traced back to their primary sources.
Manuscript sources included copies of Stainton's Manual annotated by Mathew (in the possession
of J. Firmin) and by P.B.M. Allan (in that of D.E. Wilson), together with Burrows' diary (at
present in my possession) covering the years 1871, when he was at Wanstead, and 1884-1902, when
he was successively at Brentwood, Rainham and Mucking Fitch (1891) stated that he was preparing
a list of Essex moths for publication and Burrows entered in his diary the dates on which he sent his
records to Fitch. This list was never published, but Fitch may well have given it to Harwood for
inclusion in the Victoria County History. The source of Harwood's records which are not to be found
in the literature is accounted for by this supposition.
The collections at the British Museum (Natural History) were searched for Essex specimens. To
this museum several well-known Essex collectors presented part or all of their collections; these
included Whittle, Burrows, Raynor and Huggins. Many specimens taken by Harwood, Vaughan and
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