Slowing is no good, they have to be absolutely still -- killed and fixed. It's impossible to take a stack of pictures of live animals small or large.
An entomologist friend has two "soft" techniques. One is to put the bug in the cold (portable freezer if on the field) for some time (I don't have the details) and you then have a certain amount of time before the bug begins to move again, something like 2 minutes. I don't remember the other one, maybe slight oxygen deprivation.
Andre
