It's been a long time since I played with anything like this... These are the rather beautiful larvae of the largest mosquito in the world, a resident of Sydney, Toxorhynchites speciosus. The mozzie itself is large and impressive (I'm sure I have an old photo somewhere...) and harmless to humans. These larvae are dangerous only to the larvae of other mosquito species, which they prey upon. I'd estimate these are getting up around 15 mm.