124 The Essex Naturalist
Hemiptera: P R Harvey, Coleoptera: S A Williams,
P Kirby, P R Harvey,
R G Payne. R G Payne.
Hymenoptera: P R Harvey, Diptera: D A Smith,
J Felton, R G Payne,
R G Payne, P R Harvey.
(Bethylinidae, Arachnida: P R Harvey.
Dryinidae). Crustacea: P R Harvey.
Many of the species mentioned in the following list are regarded as scarce.
Grading these species in the manner of the Red Data Books allows a rapid
assessment of the conservation status of a species based on the degree of threat.
These categories are:
RDB1 ENDANGERED Taxa in danger of extinction and whose survival is unlikely it
the causal factors continue operating.
RDB2 VULNERABLE Taxa which are quite likely to move into the Endangered
category in the near future if the causal factors continue operating.
RDB3 RARE Species not at present Endangered or Vulnerable but still at risk. Their
populations are small.
Na NATIONALLY NOTABLE
(SCARCE) CATEGORY A Taxa which do not tall into the RDB categories but
which are none-the-less uncommon in Great Britain and occur in fewer than 30
10km squares of the National Grid.
Nb NATIONALLY NOTABLE
(SCARCE) CATEGORY B Less scarce than those taxa in category A, but occur
in between 31 and 100 10km squares of the National Grid.
LOCAL Difficult to define, but such species are usually of widespread distribution but of
irregular occurrence.
ORTHOPTERA (Grasshoppers and Crickets) HEMIPTERA: HOMOPTERA
[Gryllidae Delphacidae
Gryllus campestris L. Field Cricket. There is a Asiraca clavicornis (Fab.)
pre-1970 (submitted to BRC, 1961) record for Psyllidse
"Tilbury". Remote possibility that it could once Arytaina genistae (Lat.)
have occurred on Broom Hill or Hall Hill.] Membracidae
Tettigonidae Gargira genistae (Fab.) LOCAL
Tettigonia viridissima L. Great Green Bush Cricket Cicadellidae
LOCAL Arthaldeus pascuellus (Fall.)
Metrioptera roeselii (Hagenb.) Roesel's Bush Cricket Agallia rebauti (Oss.)
Nb
Acrididae HEMIPTERA: HETEROPTERA
Chorthippus brunneus (Thunberg) Common Field Coreidae
Grasshopper Coriomeris denticulatus (Scop.)
C. parallelus (Zett.) Meadow Grasshopper Syromastus rhombeus L.