Observations of Willow Emerald Damselfly, Lestes viridis
Made
by
Kay and Peter Reeve
Visits were made to Alton Water and the River Deben, Suffolk on the
three days 19th, 20th & 21st August 2011. Two visits were made to
Alton Water (Grid ref. TM136377) on the afternoon of 19th August, 15.15
to 17.00 BST, and the morning of 20th August, 10.45 to 14.15 BST. The
River Deben near Quill Farm, Campsea Ashe (Grid ref. TM315557) was
visited on the afternoon of 21st August, 14.00 to 16.45 BST. Our
observations made of the behaviour of Lestes viridis are detailed
below. Those made at Alton Water are described in reversed day order so
that they follow chronologically the hour of the day.
Alton Water
The weather was warm and sunny on both days during the periods
observations were made. The temperature was 20°C rising a few
degrees until early afternoon. The wind was about force 2 to 3. As
noted above, the the observations are in reverse day order.
We moved away from
the car park (TM13653743) along the bank-side path
in an easterly direction at 10.45 BST. Soon individual male and female
L. viridis were seen in the herbage and on trees beside the path,
approximately 20 metres from the water's edge. They were feeding on
small flying insects in darter fashion; flying from their perch,
catching the insect and returning to their perching place to consume
the prey. None were at sites selected for breeding later in the day. In
the next 45 minutes many individuals were seen away from the water, up
to 100 to 200 metres, particularly in an area of grassland and trees
(the area in the vicinity TM13313761), mainly fairly mature oak. As
time progressed tandem pairs appeared though no copulation was observed
in this area. As the water's edge was approached, more tandem pairs
were seen but still away from suitable breeding sites. We arrived back
at the water (TM13483764) at circa 11.30 BST and soon tandem pairs were
seen arriving. After about ten minutes the first female, still in
tandem with the male, was observed ovipositing into the bark of a
Willow branch overhanging the water. More pairs were observed until
about six pairs were in view, moving from oviposition site to
oviposition site which were all on Willows. The branches selected for
oviposition varied in diameter from circa 0.5 cm. to a maximum of circa
2cm. No males were observed holding territory until circa 12.30 BST. A
slow return was made to the car park and, as time passed, more and more
ovipositing pairs, males holding territory, and pairs copulating in the
trees overhanging the water, were observed. Also, a few lone females
were seen ovipositing. There were still good numbers away from the
water feeding and basking in the sun both in the grassland/wooded area
and in an area with many large live and dead umbellifers (mainly Wild
Angelica Angelica sylvestris, grid ref. TM13483752). The non-breeding
individuals were now closer to the water's edge than earlier in the
day. We arrived back at the car park at circa 14.15 BST.
We left the car park at 15.15 BST following the roughly same route
(this is on 19th August). Immediately male and female L. viridis were
found perched, many on the live and dead umbellifers, and feeding
within 1 to 5 metres of the water. Close to and at the water's edge
there were males holding territory among the Willow branches between 1
to 3 metres above the water level and up to 1 or 2 metres away from the
water. Tandem pairs were observed ovipositing from 1 to 5 metres above
the water in the Willow branches and all those observed were over the
water. There were a few individual females ovipositing. A few
copulating pairs were also observed. Moving into the area of grassland
and fairly mature trees (mainly oaks) about 100 to 200 metres from the
water there were many individuals of both sexes evident perched in the
trees and grass. The water's edge was reached again at circa 16.15 BST
and many fewer L. viridis were seen holding territory or ovipositing
than an hour earlier. A slow return was made to the car park. Where an
abundance of individuals had been seen on umbellifers earlier in the
afternoon there were now very few. Those present were more evident
slightly further from the the water, 5 to 10 metres. By circa 17.00 BST
none were to be seen at the water. The car park was reached at 17.30.
River Deben, Campsea Ash
A visit was made to the Deben between 14.00 BST and 16.45 BST,
21st
August 2011. A length of river bank was covered from TM31515525 to
TM31005581, out and return. The weather was dull but very warm, mid
20ºC, with occasional very short bright periods.
Searches along the
first 200 metres of bank yielded sight of three
individuals on foliage overhanging the river between 0.5-4 metres above
the surface. More careful study of the overhanging trees, predominantly
Willows, produced sightings of three further males and at 15.15 BST the
first ovipositing tandem pair was found. The next 45 minutes yielded
two more ovipositing pairs and a single female ovipositing. The last
ovipositing pair were seen to separate at 16.00 BST. All the
individuals and ovipositing pairs were on Willows between 1 metre and 8
metre above the water surface. Returning along the bank from 16.00 BST
to 16.45 BST nine individuals were seen on Willows over the river,
seven males, one female and a further unsexed individual. During the
visit, in addition to those individuals over the river a number were
observed in the bankside vegetation, four females and two males. It was
noticeable that when disturbed these individuals flew up into the tree
canopies. The river was left at 16.45BST.
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