Answer: Twilight

Today’s trivia question is one where a strong recall of your old Latin lessons really pays off. Crepuscular, an English word derived from the Latin word crepusculum or “twilight,” is a zoological term used to refer to animals which are primarily active during the twilight surrounding dawn and dusk.

Many animals that people commonly refer to as nocturnal, or active at night, are really more specifically crepuscular in their activities. Many common mammals like bats, ferrets, and domesticated cats are often considered nocturnal, but in reality they engage in their primary physical activity for the day in the twilight hours and, to human observers, they appear to be active at night (when in reality they spend most of the night asleep just like humans do). Crepuscular patterns aren’t limited just to mammals, either: one of the most apparent examples of crepuscularity among insects is the flashy firefly. Fireflies have a furious period of activity every evening after the sun sets and their movement, feeding, and mating subsides as it grows darker (and cooler).

Crepuscular animals can even be further divided into matutinal (creatures only active at dawn) and vespertine (creatures active only at dusk). In our previous example, the firefly would qualify as a vespertine creature (as would most other insects with crepuscular activity patterns) because it is only active at dusk.