Diary of a farm pond: July 2011

If you are a regular here, you'll know that I'm writing a range of occasional series - 'what's in a gall', 'wildlife-friendly gardening' and so on. One of these is the diary of the pond at Highbridge Farm (Hampshire, southern England) - for pictures of the pond itself, see the April diary entry.

Events have moved on - from a summery spring to an autumnal summer, and the combination of rain and warmth has produced a lot of plant growth, plus of course the change of species with the seasons and the development of a seeded meadow around one side of the pond. It's also important to remember that this is a 'working' pond i.e. it is used for small-scale irrigation. So, what has changed recently?

Well, as expected there are more dragonflies and damselflies (Odonata) such as the blue-tailed damselfly (Ischnura elegans) below with its bright blue 'tail-light' - plus some large nymphs which must be close to emergence. Fingers crossed for some good photos of these, including some exuviae (shed skins).

Blue-tailed damselfly Ischnura elegans

Within the water itself, a number of molluscs have appeared, including the impressive (by British standards) Great Pond Snail Lymnaea stagnalis - this one is around 4cm long...

Lymnaea stagnalis feeding on algae and plant material.

Personally, I hope the mollusc community develops a taste for the algae in the pond - with warm temperatures comes blanketing algal growth; last year this was removed by hand (aided by rakes, grapples and a small boat) and I suspect this will need to be again soon. A small amount is not a problem - in fact many invertebrates seem to use it as an important moist substrate - but for the development of aquatic plants, light penetration is required which the algal can block out. Back to the aquatic molluscs - I did notice that they have an important role in the terrestrial food chain; where stranded on land, they appear to form a source of small-scale carrion, used by invertebrates that like that sort of thing...

A fly (with the silvery jowls, I think it's the common Greenbottle Lucilia caesar) guarding a dead water-snail. It almost appears to be challenging me to try and take the snail, and certainly didn't want to abandon its prize.

Once I was no longer considered a threat, the fly resumed its business - presumably feeding as I saw no evidence of egg-laying behaviour.

Staying at the pond edge, the marginal vegetation (reeds etc) is gradually developing and the structure is clearly important with a range of invertebrates using it in different ways - hunting, mating, egg-laying, pupation and emergence, feeding and so on.

A pair of 2-spot ladybirds Adalia bipunctata busily making more ladybirds on the head of a reedmace plant - important given the threat posed by the invasive Harlequin ladybird Harmonia axyridis.

Following the ladybirds' example (no, I'm not obsessed, honest - they just don't move much when mating, and so are easier to photograph), a pair of Donacia reed beetles.

Moving onto spiders, ventral view of a female Tetragnatha extensa - note the large divergent jaws.

Cautiously approaching (remember the female's jaws), a male T. extensa - as well as his own large jaws, he has two swollen palps at the front - modified structures used for sperm transfer. Onward brave spider!

I'll be following the development of the pond and its inhabitants - after all, many ponds have been lost from the British landscape and they are of key importance for nature conservation - for example, see Pond Conservation, the British Dragonfly Society, Froglife and the Freshwater Biological Association. More soon!