any area were devised. First, five species stood out from the rest from an early stage in
the survey as being very widespread indeed. These were Ischnura elegans (the Blue-tailed
Damselfly), Enallagma cyathigerum (the Common Blue Damselfly), Aeshna grandis (the
Brown Hawker), Aeshna mixta (the Migrant Hawker), and Sympetrum striolatum (the
Common Darter). These 'basic five' species were the subject of a combined distribution
map, and pending further investigation any 10 km square from which any of these
species had not been noted would be treated as under-recorded. The second measure
was to count the total number of species recorded from each 10 km square. Any square
with less than ten species would be considered under-recorded, until further recording
proved otherwise. By the end of 1983 the 'basic five' species had been recorded from
twenty-seven squares, leaving thirty squares with less than the full complement. At the
same time, only sixteen squares had reached or surpassed the total of ten species. Of the
remaining forty-one, as many as twenty-one had been credited with less than five
species.
Fig 1.1 Recording Coverage of Essex. 1980-87 (by 5 km. square)
at least one species recorded from 5 km square during survey
sites in 5 km. square visited during survey period but no records
obtained
These measures clearly targeted certain squares for careful study during the next
season, and the available recorders concentrated their activities into these unrecorded
or under-recorded squares. By this means we hoped to some extent to rectify the
unevenness of coverage of the county. By the end of the 1984 season no 10 km. square
6