Jepsen and others aren’t sure what’s causing fireflies’ numbers to fall, but they have some ideas. One ongoing danger to fireflies is light pollution, which is caused by bright streetlamps and buildings at night. It can confuse fireflies looking for mates by making it hard for the insects to see each other’s flashes.
Insecticides, which are chemicals used to kill unwanted insects, can also kill fireflies and other harmless bugs. In addition, habitat loss affects firefly populations. People clear forests and meadows to make way for roads, houses, and other types of development.
Researchers worry that climate change may affect fireflies too. Climate change has made severe drought more common in certain areas. That’s a problem for firefly larvae, which often live underground for years and require moist soil to survive. In places affected by prolonged dry periods, firefly populations have declined—likely because larvae don’t survive to adulthood.