Monday, 27 June 2016

Damselflies on the Leeds-Liverpool canal

Following my discovery of red-eyed damselfly on the Leeds - Liverpool canal the other day, I decided to do an impromtu survey today to try to get an idea of numbers between the footbridge nearest to Ramsdales hide and the footbridge near the bypass east of the flash. Conveniently this is almost exactly a 1km stretch of canal, or 0.66 miles if you're a Brexit supporter. Nothing particularly scientific about it, I simply walked along both sides of the canal and counted how many red-eyed damselflies I could see. They are one of the easier species to count due to their habit of sitting on lily pads.

In total I counted 72 individuals which included at least 10 pairs in tandem. Most of the lily pads are on the north side of the canal (i.e. the opposite side to Pennington Flash) so unsurprisingly the majority of the damselflies were also on that side.

Red-eyed damselfly, male and female in tandem.

Male and female red-eyed damselfly in guarded oviposition on a yellow water-lily.

No much else in the way of zygoptera on the canal today, except a few common blue damselflies. The pair shown here are in tandem. They are not mating, this is a form of guarded egg laying (oviposition). This pair have already mated. The female at the back is laying eggs under the water, while the male at the front stands guard by clasping her neck.

He's not particularly guarding the female, he's guarding his sperm. Even though they have already mated, the eggs are only fertilised when they are laid and the female can hold onto a males sperm for a day or two after mating before she decides to lay. This means that another male could also mate with her before laying, and in this case it may be the usupers sperm which fertilises the eggs. Therefore the original male guards her from other males and may actually induce her to lay becasue it's in his interest that she does not postpone!

Notice that this is the blue form of the female, many female common blues are green.

Fringed water-lily. These have much  smaller leaves than yellow water-lily.

Yellow water-lily has large leaves. Most of the red-eyed damselflies I saw were on the leaves of this species rather than fringed, but that maybe becasue they are easier to spot. on the larger leaves.

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