FYI - the Glow worms featured on Planet Earth were filmed in limestone caves in New Zealand.
Now that you mention it, I do believe I recall stalactites among the "webs."
(New Zealand is a whole other country, not a "surrounding island" near Australia.)
I'll admit that I was working with the simplified definition of an island as
any land that is surrounded by water, and that most definitions of island exclude continents as being defined as such. However, I don't remember referring to New Zealand as an island.
I realize it is a country composed of islands. My apologies to any New Zealander who has been offended by me not defining New Zealand.
My use of "surrounding islands" was an attempt at acknowledging
Arachnocampa can be found in places other than Australia or New Zealand (such as Tasmania, which for the record is also composed of more than one island).
If they're known to live by streams and in sandstone caves, I can't imagine why they couldn't be in limestone caves too.
Well, I'll be the first to tell you that I'm not very well educated in such things. I'm like you though, because I can't really understand what reasons there could possibly be for why they wouldn't prefer limestone caves. Obviously I've proven that they can be found in limestone caves, and their New Zealand cousins don't seem to have a problem with it. I suppose I was/am allowing the possibility that sandstone is of a different composition than limestone, and for whatever reason dismalites may not like limestone, such as a different pH level or perhaps even the texture of the rock. Sometimes animals can be picky about these kinds of things...
Thanks for your help and good wishes NZcaver! I hope to learn more about these creepy but interesting little guys.