A 98-Million-Year-Old Mantis Trapped in Amber Bears Leaf-Like Markings, Earliest Fossil Evidence of Plant Mimicry

Ninety-eight million years ago, in the mid-Cretaceous, a tropical rainforest in what is now Myanmar was oozing sticky tree resin. One praying mantis was caught in it, and the resin hardened into amber. The insect has now been described as Folimantis hyalinala, and it is the earliest clear fossil evidence of mantises mimicking the leaves of plants.

The resemblance is in the abdomen, which looks strikingly like the foliage of Selaginella grimaldii, an extinct plant also known from amber specimens found in the same region. The new name was published in the journal New Phytologist. Folimantis means 'leaf mantis,' and hyalinala points to the glass-like transparency of the creature's wings.

The authors, led by paleoentomologist Hongru Yang, note that insect-plant mimicry has been evolving for at least 200 million years, yet reliable fossil examples are scarce. They also write that this style of mimicry, imitating Selaginella, has never been reported before, and that no modern mantis species mimics Selaginella.

Modern mantises offer plenty of comparisons. Many have spent so many generations on particular plants that they have come to resemble them. The most dramatic is the orchid mantis, Hymenopus coronatus, a Southeast Asian species with a pink and cream, petal-like body that sways like a flower in the wind. Flowering plants had not yet taken over when F. hyalinala lived, so its disguise evolved toward leaves instead.

The logic of the disguise is straightforward. A mantis that looked slightly more like its host plant stood a better chance of ambushing unsuspecting prey and of avoiding its own predators. The plants may have gained as well, since mantises on them could have kept herbivorous insects at bay. Those better-disguised mantises were more likely to survive and pass on their genes, and over time the resemblance to Selaginella leaves became uncanny. The specimen shows that plant mimicry has been part of the mantid toolkit for at least 98 million years.

One feature is odd. Many modern plant-mimicking mantises carry foliar features across various parts of the body. F. hyalinala has leaf-like structures on its abdomen only. That could hint that plant mimicry began at the rear, with changes to appendages such as the wings and thorax coming later.

The deeper history helps explain how such refinement was possible. Mantises share an ancestor with cockroaches that lived around 274 million years ago, and recent taxonomic research suggests the first distinct mantises emerged about 185 million years ago, in the Jurassic, as the supercontinent Gondwana was breaking up. That long span gave them millions of generations to hone their disguises, which may account for how widespread and diverse they are. They were not alone: some cockroaches, grasshoppers, stick insects and other insect groups were also evolving plant-like features around this time. A diagram in the paper maps leaf mimicry in fossil insects against the radiation of plant species, showing how closely the two lineages' lives were bound as both expanded on land.

The specimen comes with a troubling backstory. Kachin amber mining and trade is linked to ongoing sociopolitical turmoil in Myanmar, and there are concerns that the trade helps fund what the United Nations condemns as a 'genocidal crime against humanity.' Myanmar banned fossil exports in 2015, but specimens within amber fell into a legal grey area. In 2021, after the military coup, the Society of Vertebrate Paleontology called for a 'hard moratorium' on publishing fossil specimens in amber obtained from Myanmar after January 2021.

The F. hyalinala specimen was acquired in 2015 by a collector, Fangyuan Xia, who donated it later that year to the insect evolution lab at Capital Normal University in Beijing. That date falls before the 2021 cutoff in the society's call, but the debate over Myanmar amber continues to shadow research like this.