frow what was Lexx bred?
Pill bugs are isopods which are a type of crustacean. Scientists now believe that insects evolved from crustaceans. There is another creature which is like a pill bug and may even be called a pill bug and that is the pill millipede. Millipedes and insects are in a group called uniramians.
The pill bug form is something that evolved in nature more than once and so we would expect it to evolve on other planets too. There were creatures with this form in the Dr Who story The Zarbi.
The Insects seem to be able to grow to enormous size. They also seem to be able to survive the vacuum of space. Perhaps their planet did not have an atmosphere. I would suggest that the ability to destroy planets was a technology added to Lexx and not part of its biology.
Rockham.