This is a word used to describe an organism that is most active at night. Nocturnal animals include mammals such as bats, cats, opossums, rats and mice. And then there are the owls that hunt down those rats and mice. Many kinds of insects are also nocturnal. They play an important role in pollinating plants that open their flowers at night.
Diurnal (adjective, “die-ER-null”)
This word describes a creature that is most active during the day. Many of the species we see daily fall into this category. Robins, eagles and sparrows are diurnal. Insects such as bees pollinate the flowers that bloom in daylight. And of course, no matter how late a person might like to stay up, humans are actually a diurnal species.
In a sentence
The lights diurnal humans put up to ward off the night can keep nocturnal bugs from pollinating plants.