Do insects live more during the day or at night? It's a question that has puzzled scientists for centuries. Australian researchers have now found the answer and have described it as a “groundbreaking” study.
For the first time, insect activity around the world has been mapped during day and night. “Our extensive research has allowed us to provide a definitive answer to the age-old question of whether there are more insects at night or during the day,” says researcher Mark Wong of the Space Research Institute. University of Western Australia. It turns out that insect activity increases by a third around the world during the night. But the differences between insects are significant. For example, it is important whether they live in water or on land, in the tropics or in savannas.
Difficulty of field research
You might think that it has already been determined how active or inactive insects are during the night, but this is more difficult than expected, because the methods commonly used for field research are not suitable. For example, with trawl nets, you can only catch inactive insects, while light traps do not work as well during the day as at night, which can result in a distorted image.
The researchers got around this problem by looking only at studies in which samples were collected during the day and at night using traps that specifically catch moving insects, such as pitfalls and drift nets in the water.
From the forest to the rivers
They worked through thousands of studies to finally arrive at 99 relevant studies, conducted between 1959 and 2022. In total, more than 3 million insects have been observed in different regions, from tropical forest to boreal forest and from arid forests. Grasslands to sea ecosystems.
This led to a number of interesting conclusions, which the researchers discussed nature published. There are several groups of insects, such as mayflies, caddisflies, moths and earwigs, that are mainly active at night, while bees, wasps, beetles and ants are more active during the day.
Nocturnal activity was also more common in rivers and streams. It appears that more than twice as many insects are active in the water at night. That was different on Earth. There was generally more activity during the day. Especially in grasslands and savannas, the number of flying or tumbling insects during the day can be up to three times greater than at night.
It is best not to be eaten
This difference between terrestrial and water insects probably has a common reason for any animal behavior: they want to avoid predators. “Fish hunt insects during the day, while nocturnal animals like bats make life on land more dangerous at night,” Wong said.
But temperature also plays a role. “We have discovered that insect activity peaks at night in the warmest regions of the world, because animals may escape the heat during the day,” believes the scientist, who immediately warned of the dangers of global warming.
less warm
“In the hottest regions of the world, such as the tropics, rising temperatures reduce the activity of nocturnal insects, which already suffer from the heat. Moreover, artificial light is also harmful to nocturnal animals. It disrupts their natural behavior within the ecosystem in which they live.” .
We have to do something about it, because we really can't live without insects. They are essential for plant pollination, nutrient cycling, and pest control. They perform many of these tasks at night, when they are most active.
Scientific adventure
Therefore, it is very important to continue field work and better understand what insect activity looks like, says Wong. “Such research can be exhausting, because you have to set and replace traps in many different locations several times a day. But it is extremely valuable. Insects are among the most diverse and important organisms on our planet. Studying their complex rhythms is not just a scientific adventure, but They are also essential for maintaining biodiversity on a planet that is changing so rapidly.
