Ball of Spiderlings

Observation - Ball of Spiderlings. Description: There is a 'ball' of spiderlings with yellow abdomens with a brown stripe to the rear on a small Japenese Maple outside our backdoor. I first spotted them at 9am in loose ball diameter 2.5cm. An hour later they were in a much denser ball 1cm diameter. Now

There is a 'ball' of spiderlings with yellow abdomens with a brown stripe to the rear on a small Japenese Maple outside our backdoor. I first spotted them at 9am in loose ball diameter 2.5cm. An hour later they were in a much denser ball 1cm diameter. Now (1:30pm)they are in the looser arrangement with a network of silk. I am intereted in species and the behaviour. Are these new hatchlings about to disperse? Spiderlings are still in a ball at 9:50 am on 28/05/10