Not all dams are created equal

One would think that in any given area one dam would be much the same as another in terms of the existing biota. I am not sure it’s that simple.

In my neighbour’s dam at about this time of the year dusk signals the time for dragonfly nymphs to leave the water by climbing up the reeds and emerge as adult dragonflies. It is quite a remarkable spectacle. But in my dam, nothing. The only things ascending are myriad of mosquito bites on my arm as I sit fruitlessly watching for anything to emerge. Recently I travelled ‘over the hill’ to investigate someone else’s farm dam. To my surprise the reeds were populated by a type of spider I had never seen before, Long-jawed Spiders (Tetragnatha sp.), lots of them, pictured below.

Long-jawed spiders are elongated orb-weavers building small orb webs in vegetation bordering waterways. Their jaws are often more than half the size of their bodies. They eat arthropods trapped in their webs or capture by stalking them and are excellent at walking on the surface of water travelling faster on that surface than on land.

That’s all you need. A spider with extra large jaws that can walk quickly on land and water.