Monday, 11 July 2016

Life on a canal

This afternoon I spent a couple of hours along the tow path of the Leeds - Liverpool canal at Pennington Flash, between the footbridge near Ramdales (Common Lane) and the footbridge near the Atherliegh Way (Pilling Street). I was hoping to have a further look at the red-eyed damselflies I found there a couple of weeks ago, plus anything else I might find.

There were still plenty of red-eyed damselflies on the wing, where two weeks ago I counted 72 on this stretch of canal. On that occasion I walked along both banks, but today I only had time to visit the less productive south bank, but I still managed to count 25 individuals, including at least 5 pairs in tandem, so overall numbers were probably pretty similar.


I managed to photograph a few in tandem, or guarded oviposition. There's nothing romantic about dragonfly or damselfly courtship, the males just grab the females and cling on. After mating the males of some species including red-eyed damselfly grab the female by the neck and guard them from other males. This is because the eggs are not fertilised until they are laid, therefore it's possible that another male could grab the female and mate before the eggs are laid thereby usurping the original male. This means that any pair in tandem is constantly harassed by single males who are trying to dislodge the original male. Even males of other species will show aggression towards pairs.


Common blue harassing a pair of red-eyed damselflies.


The pair even fly in tandem.



The female egg laying.


I'm sure that some females must drown during egg laying, this one was forced under water by the male for at least a minute!

I also managed to photograph a couple of other species of damselfly in tandem today, namely common blue and Azure.


Azure damselflies.


Common blue damselflies. The male at the back is up to no good.

 
Common blue damselfly. Notice what looks like a water vaneer moth Acentria ephemerella just below the damselfly. I didn't notice this in the field.


I was made up to spot this beauty hunting on the lily pads! This is Pirata piraticus or Pirate Wolf Spider. It hunts by holding its front legs on the surface of the water and sensing any movement from an unfortunate insect, which it then sprints across the water to claim, causing barely a ripple on the surface.



Touching the water but you'd barely know it! There's hardly a crease in the surface!


I've seen tufted ducks with chicks on the canal in previous years, and I still don't know where they nest. Nowhere obvious that's for sure.


Apart from the two species of water lily on the canal (fringed and yellow), there is also arrowhead Sagittaria sagittifolia, which is part of the water-plantain family.


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