Alive they look all black, but the first time I saw these, they were pink, having drowned in a pool of water, so I think of them as ‘prawnies’! I have no idea what they are really, but their overall shape is also suggestive of a prawn. Clearly, that they can drown, suggests their structure & movement adaptations do NOT suit them to water! I’ve since seen them in damp soil under logs etc, and they spring about energetically when disturbed. At night during significant rain they may come into the open, as if to avoid the wet.