In dire circumstances, a vampire queen may choose to "swarm" and leave her hive with her brood of vampires. An older queen must find and claim a new location within a matter of hours, or risk perishing due to over exposure to the sunlight. A newly made queen has months to settle into a hive. Swarming is particularly distressing to a queen, as the tether to her territory must be broken and reforged. (It may be noted, however, that roves like Lord Akeldama may swarm as he did in Blameless, but there is not the same urgency behind finding a new location as there is in a traditional hive, likely due to a fewer amount of vampires being relocated, and the tether being weaker).
The swarming vampire becomes physically panicky, showing jerky movements and startling easily.
If a vampire queen is killed while the hive is awake, the surviving vampires will swarm, entering a mindless, murderous rage until death[1]. A swarm without a queen can lead to catastrophic loss of human life, as evidenced by the hundreds slaughtered in Paris after Major Channing murdered one of its hive queens[2]. Vampires were abolished in France as a result (though many still reside there). Chancellor Neshi once explained to Alexia Maccon that if a vampire queen were to die during the daytime, while her hive slept, the other vampires of her hive would peacefully die with her, "travel[ling with her] into the afterlife"[1].