question:  Why have humans been carrying beetles around the galaxy?
context: Two hours since, the sun of this solar system had been a vast glaring disk off to port, with streamers and prominences erupting about its edges. The ice-cap, by its existence and circular shape, proved that the planet rotated at a not unreasonable rate. A water-ice ice-cap said that there were no poisonous gases in the planet's atmosphere. A small one like this meant wide tropical and sub-tropical zones. The fact was verified by the thick, dense cloud-masses which covered most of the surface,—all the surface, in fact, outside the ice-cap. But since there were ice-caps there would be temperate regions. Two of the Nadine's four-man crew watched out the same ports as the planet seemed to approach. They didn't seem to resent what he'd tried to do, or that he'd brought them an indefinite distance in an indefinite direction from their last landing-point, and they had still to re-locate themselves. Without rigid control of space-travel, any criminal anywhere could escape the consequences of any crime simply by buying a ticket to another world. Wherever the yacht landed, such a disparity between its documents and its crew would spark an investigation. It could have travelled at almost any speed in practically any direction for a length of time that was at least indefinite. The process would be to find a planet and check its climate and relationship to other planets, and its flora and fauna against descriptions in the Directory. It marked a first-landing spot on some planet or other, so the people could find that spot again. If they left a beacon, they may have left an identification of the planet. If somebody were wrecked on an even possibly habitable planet, the especially developed seed-strains would provide food in a minimum of time. But space-travel regulations are especially designed to prevent such escapes. One of the controls on space-traffic required a ship on landing to deposit its fuel-block in the space-port's vaults.
output:  Beetles are just one piece of the puzzle to create an ecological system capable of supporting human life.
options:  Beetles are just one piece of the puzzle to create an ecological system capable of supporting human life.  Beetles are a good source of protein for new planet settlers.  Beetles, like other pests, always seem to make their way on board spaceships.  Beetles are an integral part of a spaceship's waste management system.