Insects can be so tiny we might not always think about them, but they play a really important role on our planet.
Many birds and reptiles rely on them for food and they also help with pollination.
New research has been looking at historical reports of insect declines from across the globe.
They've also been looking at the reasons why it's happening.
The most affected species include moths, butterflies, dragonflies, wasps, bees, ants and dung beetles.
Some insect species are increasing though.
The research, published in the Biological Conservation journal, found that 40% of the world's insect species could become extinct over the new few decades.
That means they wouldn't exist any more.
The researchers say there are a number of reasons for the drop, including loss of habitats because of intensive agriculture and climate change.