The remainder of the county shows high diversity in the south and east, with
a marked peak in the Southend area due both to entomological merit and
intensive recording; a second area of high diversity lies in the north-west on the
surface chalk, these two being separated by a belt of low diversity.
Correlation with this pattern will be found on the map entitled 'The surface
geology of vice-counties 18 and 19' attached to the end cover and Map 16 'Land
Use' in Jermyn (1974). Low species density corresponds with glacial till
(boulder clay) which in turn corresponds with arable farming. Boulder clay
itself is not unsuitable for insects as can be observed where there is still
woodland; for instance Chalkney Wood near Earls Colne is on the boulder clay
but is nevertheless an excellent entomological locality. But apart from the few
woods, the whole region is under such intensive arable farming that hardly any
waste ground or other type of habitat suitable for insects remains. Jermyn
(p.35) discusses the effect in this region of the uprooting of hedgerows (about
35% of the total), the use of sprays and defoliants and the destruction of
deciduous woodland. My own experience in this belt is that the micro-
lepidoptera are fewer and harder to find; that it is also poor for the macrolepid-
optera is shown by the lack of named localities on the 'Map of Essex' in Firmin
et al. (1975).
The geological map shows a great variety of soil in the south and east and the
map depicting land usage a predominance of permanent pasture. Essex is rich
in coastal species and others which are not strictly coastal are more plentiful
close to the sea. The climate of the south-east is more suitable for the species
on the fringe of their range. Immigrants make their landfall in the south-east
and thence often progress up the Thames estuary. These factors all combine to
make the south and east of Essex one of the best areas for moths in the whole of
the United Kingdom.
In some respects the north-west has more affinity with Cambridgeshire than
with the rest of Essex. The surface chalk must have formed downland before
agriculture took over. Chalk-land plants such as marjoram and rockrose still
occur on the roadside verges and support species not found elsewhere in the
county. The entomological merits of the north-western woodlands will be
discussed below.
Thus the pattern of the two areas of abundance separated by a belt in which
insects are scarce is factual and not occasioned by the caprices of recording.
The low-yield belt tends to act as a barrier separating differently composed
associations of species. The maps depicting Taleporia tubulosa (p. 40), Epagoge
grotiana (p. 107), and Endotricha flammealis (p. 140) are typical of common
insects found only in the south and east, whereas those for Stephensia
brunnichella (p. 72), Biselachista cinereopunctella (p. 74) and Telephila
Schmidtiella (p. 93) show species confined to the north-west.
Types of habitat
(1). Woodland. Essex contains the ancient forests of Epping, Wintry,
Hainault, Hatfield, Writtle and Colchester (Kingswood); to these may be
10