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Megabunus diadema (Fabricius) Plate 16
National status Common County status Essex Scarce Threat status Essex Threatened
Frequency Ratio 1.2 Tetrad Percentage 0.6 Tetrad Frequency 1.9 Monad Frequency 1.4
Distribution
Extremely rare in scattered sites in the
north of the county nearly always as
singletons.
Habitat and Ecology
The species has been recorded from
ancient woodlands, in well-rottcd leaf litter
and on a lichen-covered oak trunk.
Nationally it typically occurs in damp
woodland, sometimes on lichen-covered tree
trunks, rocks and heather and appears
commoner in the wetter and upland parts of
Britain (Sankey 1988; Hillyard & Sankey
1989). Its scarcity in Essex and restriction to
damp woodlands in the north-west and north
of the comity despite the county's large
amount of ancient woodland is probably explained by the low rainfall, in south-east Essex the
lowest in Britain.
Adults have been recorded in May.
Threats
The species is threatened by degradation or loss of woodland habitat and the current
evidence for climate changes suggests it will become generally threatened in south-eastern
England.
Rilaena triangularis (Herbst)
National status Common County status Essex Ubiquitous
Frequency Ratio 3.0 Tetrad Percentage 15.9 Tetrad Frequency 50.0 Monad Frequency 42.9
Distribution
Common and frequent in the county.
Habitat and Ecology
Especially associated with the ground
and field layers of woodland but also
recorded in a wide range of other habitats
including scrub, herbage, acid grassland,
rough grassland, grazing marsh grassland,
roadside verges, dunes and marshes.
Adults are recorded from April to July
with a peak in May-June.
Threats
Not threatened.
Essex Naturalist (New Series) 16 (1999)