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THE DISTRIBUTION MAPS AND SPECIES ACCOUNTS
The county boundary used here is Watsonian Essex as defined by the Ray Society publication
No. 146 'Watsonian Vice-counties of Great Britain'. The distribution maps have been produced
using DMAP, a mapping program developed by Dr Alan Morton. Tetrad maps have been
chosen as a comproimse between recording coverage and the ease of assessing distribution
patterns. Circles represent records from a tetrad within the county. Closed squares represent post
1980 records and open squares earlier records (although almost all records before those of P.V.
Hicks between 1969 and 1977 cannot be assigned with tetrad accuracy).
Frequency Ratio, Tetrad Percentage, Tetrad and Monad Frequencies are discussed and defined
earlier in the text. The Frequency Ratio is the proportion of post 1980 tetrad to 10km square
records. Tetrad Percentage is the number of post 1980 tetrad records as a percentage of the total
990 tetrads in the county. Tetrad Frequency is the number of post 1980 tetrad records as a
percentage of the 314 tetrads in the county with Harvestmen records. Monad Frequency is the
number of post 1980 one km records as a percentage of the 415 one km squares in the county'
with harvestmen records.
Nomenclature follows the checklist in Hillyard and Sankey (1989).
OPILIONES
FAMILY NEMASTOMATIDAE
Nemastoma bimaculatum (Fabricius)
National status Common County states Essex Ubiquitous
Frequency Ratio 2.5 Tetrad Percentage 13.5 Tetrad Frequency 42.7 Monad Frequency 37.6
Distribution
Recorded widely across the county in a
variety of habitats, a common and often
frequent species.
Habitat and Ecology
The species has been recorded from
grassland, scrub, hedge bottoms, woodland
and marsh habitats. Sankey (1988) describes
the species as widespread and common in
deciduous woodland litter, in loose moss,
and also in rank grassland, under logs,
stones, etc. in gardens and cultivated areas.
Both note that adults have been recorded
in all months, a situation reflected by our
rccords with high numbers of both sexes
recorded in most months but peaks in the
autumn and spring.
Threats
Not threatened.
Essex Naturalist (New Series) 16 (1999)