Leaf miners identified as oldest insect plague in the history of Earth

Gaby Clark
scientific editor

Robert Egan
associate editor

Paleontologists, including researchers from the Museum für Naturkunde Berlin (MfN), have described the oldest insect larval feeding tunnels inside leaves, also known as leaf mines, along with associated egg deposits, based on plant fossils. The frequency of leaf mine infestations in fossil plants is spectacular and can be described as the oldest insect infestation in the history of Earth.
The findings, which are housed in the collection of the MfN, among others, show that this highly specialized behavior of insect larvae already existed 295 million years ago, around 40 million years earlier than previously assumed. This once again underlines the relevance of natural history collections.
Whether you are a farmer, gardener or walker, you have probably noticed the intricate feeding tunnels made by insect larvae inside leaves, also known as leaf mines. Living inside plant tissue has many advantages, such as protection from predators, dehydration, and harmful environmental influences. In addition, the larvae have an almost inexhaustible supply of food at their disposal, like a pig in clover.
Nowadays, leaf mines are produced exclusively by insects such as beetles, dipterans, wasps and butterflies, which undergo complete transformation (metamorphosis) and are therefore referred to as holometabolous insects. They are highly adaptable and, in the course of evolution, have developed slender, maggot-like larvae without body appendages that are optimally adapted to life inside plant tissue.

Until now, it was unclear when this successful strategy emerged among insects. The oldest reliable evidence of leaf mines to date comes from the Triassic period, the early Mesozoic era.
By using state-of-the-art research methods, a team of scientists from the natural history museums in Chemnitz, Berlin, Münster and Osnabrück, the TU Bergakademie Freiberg and Martin Luther University Halle-Wittenberg has now been able to prove that leaf mines existed more than 40 million years earlier than previously assumed. The paper is in the journal Scientific Reports.
The researchers had access to the extensive paleobotanical collections of the natural history museums in Berlin, Schleusingen and the Freiberg University of Mining and Technology, which proved to be veritable treasure troves for science: These collections contained numerous exceptionally well-preserved specimens of the feeding traces of Asteronomus maeandriformis on leaves of the seed fern Autunia conferta, which originate from approximately 295 million-year-old deposits from the Permian period in the small former coal mining area in Crock, Thuringia (Germany).
The perfectly preserved plant fossils allowed the unequivocal conclusion that insect larvae created the feeding tunnels protected inside the leaves. In addition, it was possible to identify the egg deposits associated with the feeding tunnels, which in some cases even contained remains of insect eggs.
The frequency of these fossils is remarkable: in total, more than 80% of all Autunia plants from Crock were infested with leaf mines, which can rightly be described as the oldest insect infestation in the history of Earth. Why exactly the Autunia plants in the Crock locality were intensely widely infested remains a mystery. However, the phenomenon occurred at a time of global change, during which tropical terrestrial ecosystems gradually became drier.
More information: Michael Laaß et al, Host-specific leaf-mining behaviour of holometabolous insect larvae in the early Permian, Scientific Reports (2025).
Journal information: Scientific Reports
Provided by Natural History Museum, Berlin