Purple-scum Springtails (Hypogastrura vernalis) - Collembola - congregating on swimming pool at Forest Hill, Melbourne, Victoria, Australia. Photographed on 28 May 2009.c. 1mm in lenth. They congregate in thousands on the surface of the pool.see Greenslade, P., et al. (2014). Biology and key to the Australian species of Hypogastrura and Ceratophysella (Collembola: Hypogastruridae). Austral Entomolgy 53(1): 53-74.www.inaturalist.org/observations/55659751