At least four species of Crow butterfly (Euploea) are found in the Townsville region, three in the immediate vicinity and the other at least as close as Jourama Falls to the north.
Here are two of them together: E. sylvester, the Two-brand Crow, is perched above E. core, the Common Crow. It is not too hard to tell them apart when they are seen together like this (the large white spots follow the edge of the wing in E. sylvester but cut straight across in E. core) and the third local species, E. tulliolus, (photo here) is even more distinctive. But they are all much the same size and coloration and in isolation are easily mis-identified.
I found them in a large mixed aggregation* on the edge of Townsville’s Town Common on my visit a fortnight ago. Peter Valentine tells us that this behaviour is normal in the Dry season but you have to be in the right location to see it – in this case, a patch of cool, dark, damp woodland at the foot of Bald Rock, just near the bird hide. Dozens of them, perhaps hundreds, were in constant motion, restless but never flying far. All they are doing, really, is passing the time until the Wet, their breeding season, arrives.
* Flock? Swarm? Wikipedia tells me that the correct collective nouns for butterflies are ‘flight’, which sounds okay, or ‘rabble’, which doesn’t and isn’t even dramatic like the collective noun for feathered crows, ‘murder’. None of them seem quite right.