The cockroach team was trying to invent a lifeform which would migrate from pole to pole of Scoti in order to get the benefit of multiple successive summers. Our approach was based around an insect-style life cycle: after hatching, we had a larval stage followed by a short breeding stage. The breeders mate in late summer, then fly to the opposite pole to arrive there in spring. They land in the water, dump their eggs, and die. (Presumably therefore only the egg-carrying sex of the breeders actually needs to make the journey; the other sex's job is done once it's mated.) The young hatch out and immediately have the whole summer in which to grow up.

Initially, the life cycle was going to be synchronised with the half-year, so that the spring hatchlings had reached breeder stage by the end of the same summer, and the creatures never needed to survive a winter at either pole. We abandoned this idea because it would have made sentience tricky to achieve: if you can't pass knowledge and communication between generations, you have a hard time building a civilisation. So instead we decided that the larvae would _also_ have to be able to hibernate, and would last several years at the same pole where they were born, before finally breeding and migrating to the other pole; I suppose this means the only remaining advantage of migration is not having to have winter- resistant eggs, which isn't as convincing a justification as not needing to have winter-resistant anything.

We thought this would be a fun alien to evolve sentience in, because of the fact that the populations at each pole would constantly exchange children but would never communicate any _information_, so there'd be no particular reason why they'd reach (for example) the same tech level at the same time, or speak the same language, or anything. Presumably someone would eventually manage to establish pole-to-pole communication by sellotaping Pioneer-type diagrams to breeders before they took off... In the meantime, though, child- rearing would be entirely communal because nobody knew the ancestry of anyone, and the annual arrival of young would be a stork-style delivery from heaven.