Dragonfly and Damselfly monitoring on the Writtle College estate - the first five years
Eight species of Dragonfly were observed on the College estate (Table 3), with Common Darter
Sympetrum striolatum the most abundant species. However, Dragonflies occurred in less abundance
than Damselflies; there were only 132 observations of S. striolatum during the entire monitoring
period compared with 2864 of C. splendens. Rarities for the monitoring period include Emperor
Dragonfly Anax imperator and Broad-bodied Chaser Libellula depressa with fewer than six
observations each.
Table 3. Total number of individuals and status of all Dragonfly (Anisoptera)
species recorded over the five year period
Species Total number of Status
individuals
Sympetrum striolatum (Charpentier) 132 W + VC
Sympetrum sanguineum (Muller) 83 W + C
Aeshna grandis (Linnaeus) 65 W + C
Aeshna mixta (Latrielle) 49 W + C
Aeshna cyanea (Muller) 32 W + FC
Orthetrum cancellatum (Linnaeus) 8 R
Anax imperator (Leach) 5 R
Libellula depressa (Linnaeus) 4 R
_______________________________________Total____________378_____________________
W + VC = widespread and very common
W + C = widespread and common
W + FC = widespread and fairly common
R -rare
Changes in the number of individuals and species that were recorded each year were evident during
the monitoring period (Table 4). The total number of individuals per visit increased over the four
years from 1997 to 2000, but numbers declined to a low level in 2001. Species richness increased
from 11 in 1997 to 14 in 1999 and 2000. However, only 12 species were observed in 2001.
Table 4. Total number of individuals per visit and the number of species recorded
Year Individuals per visit No. of species
1997 112.2 11
1998 122.8 12
1999 160.4 14
2000 188.8 14
2001______________98.1_________________12________
Increases in the abundance for all species were noted in several transect sections including Sections
2, 6 and 8 (Table 5), the latter of which being along the slow-flowing River Wid (Fig. 1). There
were no substantial declines in abundance on any transect sections during the monitoring period.
Abundance was greatest in Sections 3, 6, 7 and 8 over the five years, with these sections having
suitable bank-side vegetation. Sections 6, 7 and 8 were all alongside the Rivers Can and Wid,
which are relatively slow-flowing and have six-metre grass field margins adjacent to the water's
edge. Still water habitats such as the Moat (Section 3) were not well-represented habitats on the
transect, but Odonata were abundant at this site. Unfavourable habitats for Odonata include Sections
1, 4 and 5. The former section is mainly woodland, managed with a policy of non-intervention,
whilst Sections 4 and 5 predominantly comprise amenity grassland habitats and roadside verge.
Essex Naturalist (New Series) 19 (2002)
103