I see them every year and they never fail to intrigue and excite me. We have several species of moths in the family Hepialidae which visit our property, but by far the most numerous and most spectacular is the species Trictena atripalpis.
They usually all emerge on the same night and are drawn to our house lights, as you can see above.They need to emerge together because they only live for one night, so they must find a mate and the females must lay their eggs on the night. The trigger for their emergence is heavy rain, and we had quite a dump last night, about 40 mm or so.
In the morning there were only a few survivors left. During the night they were systematically picked off by owls and bats, and in the morning the day birds got the rest. I was only able to find two surviving moths around the house in the morning. The image below shows one of them. It should give you a pretty good idea of their size!
These moths emerge from underground, because their larvae are root feeders, leaving a pupal skin poking out of the ground. Sometimes just the tip of the skin is poking out of the ground, like in the image below, but on other occasions the entire skin is accidentally hauled out onto the surface.