What sign indicates that a hive is ready to swarm?

The presence of swarm cells is a clear indicator that a hive is preparing to swarm. Swarm cells are specially constructed queen cells that house developing queen larvae. When a colony becomes overcrowded or conditions in the hive suggest that it's time to reproduce, the bees will start to raise new queens in these swarm cells. As the new queens develop, the current queen will eventually leave the hive with a portion of the worker bees, leading to the swarming process.

The other options, while they may indicate aspects of hive health or activity, do not directly signify that a hive is ready to swarm. For instance, large amounts of pollen collected suggest good foraging conditions and hive health but do not specifically relate to swarming behavior. Similarly, a dark honeycomb structure indicates an older comb that has been used for brood or honey storage but lacks direct connection to the swarming process. Lastly, a high drone population is often associated with mating activities but does not necessarily indicate that the colony is preparing to swarm. Collectively, these factors may contribute to overall colony vitality, but swarm cells are the definitive sign that a swarm is imminent.