Eureka! Lab | Student Science

Support Strong Science

Be a champion now for the

next generation of science leaders.

Eureka! Lab

A place for discovery 
Bethany Brookshire

Eureka! Lab

Scientists Say

Scientists Say: Crepuscular

These animals prefer the dim glow of twilight

Eureka! Lab

Fireflies are crepuscular insects. The dim light of evening helps their flashes stand out. 


Crepuscular (adjective, “Kreh-PUS-kew-lur”)

A word to describe an animal that is active in twilight — dusk or dawn. Animals active during the day are diurnal. Those active at night are nocturnal. Some animals in desert environments are crepuscular to avoid the heat of the day. Other animals — such as fireflies — are crepuscular so their flashing signals shine bright. 

In a sentence

When using an app that tracks fireflies, you might want to wait until dusk to capture the crepuscular bugs.

Follow Eureka! Lab on Twitter

Power Words

(for more about Power Words, click here)

app     Short for application , or a computer program designed for a specific task.

bug     The slang term for an insect. Sometimes it’s even used to refer to a germ.

crepuscular    An adjective that describes animals that are active during twilight.

diurnal   An adjective for some activity that is done during the day, or some organism that is active during the day.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

nocturnal     An adjective for something that is done, occurring or active at night.

Readability Score: 
7:00am, July 25, 2016
A poison-arrow frog is poisonous, but a rattlesnake is not. What’s the difference? It’s how their poisons are delivered.
7:00am, July 18, 2016
A poison-arrow frog is poisonous, but a rattlesnake is not. What’s the difference? It’s how the poison is delivered.
poisonous mushroom
7:00am, July 12, 2016
Keeping kids in school for a few extra hours could mean better reading comprehension — no matter how the teachers use the time. But those extra hours come with extra cost.
class time
7:00am, July 11, 2016
As plastic floats in the ocean, it can acquire its own colony of microbes and algae. We call this ecosystem the plastisphere.
plastic mask
7:00am, July 6, 2016
Germs are everywhere. One teen has designed a way to keep them from sticking to a surgeon’s gloves.
7:00am, July 5, 2016
It is safe to refer to any poison as toxic. But while all toxins are poisonous, most poisons are not toxins.
poison frog
7:00am, June 29, 2016
Cyanides are poisonous. But they are more than that. This group of compounds is used in everything from mining to capturing fish.
7:00am, June 22, 2016
Inspired by a classroom experiment, a teen has built a way to lure troublesome termites to their death — using the power of ink.
7:00am, June 20, 2016
Scientists have predicted the presence of tunnels in space that connect two points in space and time. They are named for the shape they resemble.
7:00am, June 13, 2016
For a cell to remove something large from inside itself, it turns to a process called exocytosis.
Subscribe to RSS - Eureka! Lab

From the SSP Newsroom

Science News


Science News for Students


Eureka! Lab