Amber from the Cretaceous Period reveals the secret of the behavior of trichopter insects and their disappearance 50 million years ago

Ecological reconstruction of Copulariella ramus. Credit: Wang, Engel, Zhang, Shih et Ren 2024. Painted by Ms. Xiaoran Zuo.

doi.org/10.1093/nsr/nwae227
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A recent study found that the swarming behavior of caddisflies (a group of moth-like insects) began millions of years ago, but died out about 50 to 53 million years ago because of bats that use echolocation to hunt. Bats can’t detect the sounds bats make, which has put them in danger.

Scientists led by Professor Dong Ren and Dr. Jiajia Wang from Capital Normal University analyzed pieces of amber (fossilized tree resin) that were about 100 million years old. Inside these pieces of amber were groups of adult caddisflies that showed signs of swarming behavior.

Origin of Swarming:

To understand when and how caddisflies began to form swarms, scientists used analyses of the physical and genetic characteristics of several caddisflies. These analyses indicated that swarming behavior had existed since the Triassic period, more than 200 million years ago.

Why Did Swarming Disappear”

Scientists realized that about 50 to 53 million years ago, many types of caddisflies stopped forming swarms. This period coincided with the emergence of echolocation bats. Echolocation is a system that bats use to “see” in the dark through sounds. Since caddisflies cannot hear these sounds, bats had an advantage when hunting these insects.

Researchers believe that, to protect themselves, caddisflies stopped forming large groups. This happened during a time called the Eocene, when many nocturnal predators emerged.

The ancestral reconstruction of swarming behavior based on morphological and molecular data using a Bayesian total-evidenced dating method with a molecular backbone constraint. The data source of trichopteran species comes from GenBank and NCBI. Credit: Jiajia Wang

Bats” Impact on Trichopterans

The study`s results show that the presence of nocturnal bats helped shape the behavior of trichopterans over time. Unlike birds and other flying predators of the past, which hunted during the day, bats hunted at night, precisely when trichopterans usually swarm. As a result, these bats were a greater threat.

This disappearing swarming behavior may have been one reason why trichopterans evolved to have less diversity than their “close relatives,” butterflies.


Publicado em 10/21/2024 10h25


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