What are those tiny spiders drifting in the air on silken strands?
During late summer and autumn, a walk across a field in the early morning will reveal a mass of fine silken strands shimmering and drifting in the sunlight.
These silken threads can be seen virtually anywhere as they are produced by tiny spiders attempting to disperse to find new areas. Most insects have wings with which they can escape predators, travel to find food, mates and new places to live. Spiders lack this long-distance mode of transport. Young spiders, especially, need to disperse in order to improve their chance of survival. They do not want to compete with their parents and siblings so they need to 'get away'. To do this they climb blades of grass, fence posts or any structure that will get them off the ground, then they point their abdomen into the air and release silk.
The silk hardens and more is pulled from the spiderling as the wind catches it. Eventually the thread is sufficiently long that, when the wind blows, it can pick the spiderling up and lift it into the air like a kite set free when you let go of the string. The spiderling may travel a metre or so or hundreds of kilometres. For example, spiderlings on silk have been found at thousands of metres above the Hawaiian islands, the remotest island group on earth. This method of travelling is called 'ballooning', perhaps an inaccurate word as it implies that the spider is suspended on something that is 'lighter than air' when it is in fact caught on the end of a fine thread that is being whisked away on the wind. 'Kiting' might be a more appropriate description of the process.
Spiderlings of several families disperse this way, particularly the so-called 'money spiders' of the family Linyphiidae.