Larvae Mischievous spectres. The larva or ghost of Caligula was often seen (according to Suetonius) in his palace.

I never heard this word used this way before. Since it must be older than our use of the word to mean
very immature form of an organism, that use seems poorly chosen.
Dr. Bill, in one of my Mary Stewart books, a little girl is being shown things in nature by her cousin, a "wise woman". They see a larva pupate, and the little girl mishears "a nymph", and says it is "an imp". It took me a while to remember that much detail; at first I was thinking that I'd read that larvae really were called imps. So I tried looking it up, and look what I found:
[Old English impa "young shoot, scion" and impian "to graft," both ultimately from Greek emphuein , literally "to emplant," from phuein "to grow, plant"] There really does seem to be a connection!