Changes in macro-moth abundance on the Writtle College estate, 1968-1993
TIM GARDINER AND ROBIN FIELD
Writtle College, Lordship Road, Writtle, Chelmsford, CUI 3RR
Abstract
A Rothamsted light trap was operated at Writtle College from 1968 until 1993 with 345 species of
macro-moth recorded. The total number of individuals captured per year fluctuated considerably,
although a slight increase in the total number of species recorded each year was noted, possibly
facilitated by the creation of many conservation areas on the Writtle College estate since the 1970s.
Several uncommon species were identified which are included in the Regional Action Plan for Anglia.
Introduction
Rothamsted light traps have collected moth records for many years in the British countryside, although
the data remains under-analysed and under-valued (Young 1997). The catches on every night of the
year are killed and analysed, with the trap designed to be inefficient in order to catch and kill only
moderate numbers of moths (Young 1997). A Rothamsted light trap collected moth records from
1968 until 1993 at Writtle College and this paper aims to highlight changes in macro-moth abundance
and occurrence over this period.
Methods
Writtle College is located in the south-east of England, two kilometres from Chelmsford in Essex
(TL 670070). The College estate extends over 210 hectares and consists of agricultural, horticultural
and conservation areas. The Rothamsted trap was positioned to the north of the main College buildi og
(TL 678071) with the catch for each night of the year being recorded from 1968 until 1993. In 1973,
1982 and 1983 trapping was not conducted. Throughout the 23 year monitoring period, mainly
macro-moths were recorded, although in 1977 and 1978 micro-moths were identified with assistance
from Lt. Col. Emmet of Saffron Walden (Neate 1979). The scientific names follow those in Skinner
(1998) and Stace (1997).
Results
A total of 39,953 individual macro-moths comprising 345 species were recorded over the monitor-
ing period. The total number of individuals caught each year fluctuated considerably with 1975 and
1976 displaying greatest moth abundance (Figure 1). The total number of moths did not decline
significantly. The total number of species, however, increased towards the end of the monitoring
period, but the greatest number of species were recorded in 1975 and 1976.
Essex Naturalist (New Series) 18 (2001)
139