Large bats repeatedly hover outside Lucy's and Mina's windows, embodying the night visitor while vampire-bat lore helps Quincey name the blood loss.
A great bat repeatedly wheels outside Lucy Westenra's window as she grows pale and wakes with throat wounds. Another passes above Renfield at the instant his fury changes to calm, linking the creature's movements with the Master he senses.
Quincey Morris recalls vampire bats draining horses on the pampas, giving the hunters an animal precedent for blood loss without obvious attack. The recurring form suggests how Dracula watches and travels while avoiding ordinary human notice.
A large dark bat with broad silently flapping wings, seen circling windows and crossing moonlit sky; vampire bats are associated with tiny bites and severe blood loss.
Bats are both Dracula-associated nocturnal forms and the natural analogy that lets Quincey frame Lucy's impossible depletion as literal feeding.