This bug event is a bit of a mystery but the red ones do appear to be nymphs.
Flies such as these settle on the surface of natural springs in the Flinders Ranges. The secret of their buoyancy is revealed in the shadow.
Female raspy cricket with ovipositor projecting from abdomen.
Scolopendra mortisans, 110mm.
Leigh Creek Library has an excellent range of field guides including the following titles.
Likely to be Trictina atripalpis moth, also known as the Rain Moth. 100mm.