An exceptionally well-preserved light-producing beetle, which resides in amber for 99 million years, sheds light on the diversification of bioluminescent insects in the Cretaceous Period.
With more than 3,500 species described, light-producing beetles are the most diverse of bioluminescent terrestrial animals. Fireflies, fire bugs, firefly beetles and their relatives use light to ward off predators, attract mates, and some females even use light to lure unsuspecting males. Historically, despite its diversity, the evolution of bioluminescence in beetles has been poorly understood.
“Most of the light-producing beetles are soft in shape and quite small, so they found few fossils. This new fossil, found in amber from northern Myanmar, is exceptionally well-preserved, including the organ of light in its belly. intact, ”explains Dr. Chenyang Cai, a University of Bristol researcher and associate professor at NIGPAS.
The presence of a light organ in the male’s abdomen provides direct evidence that the adults of ‘Cretophengodes’ could produce light about 100 million years ago.
“The newly discovered fossil, faithfully preserved in amber, represents an extinct relative of fireflies and the living families ‘Rhagophthalmidae’ and ‘Phengodidae,'” notes Yan-Da Li of the Nanjing Institute of Geology and Paleontology (NIGP) and Beijing University in China.
Most of the light-producing beetles belong to the gigantic superfamily Elateroidea with about 24,000 known species and thousands waiting to be described. The discovery of this beetle forms the missing fossil link between living families, helping scientists understand how these beetles evolved and how they should be classified.
“Elateroidea is one of the most heterogeneous groups of beetles and that has always been very difficult for entomologists, especially as important anatomical innovations evolved independently many times in unrelated groups. The discovery of a new family of extinct elateroid beetles is important because it sheds light on the evolution of these fascinating beetles, ”explains Erik Tihelka of the Faculty of Earth Sciences.
“We believe that light production initially evolved in the soft, vulnerable larvae of the beetle as a defense mechanism to ward off predators. The fossil shows that in the Cretaceous period, the production of light was also absorbed by adults. It could have been co-opted to fulfill other functions, such as mating, ”says Robin Kundrata, an expert on elateroid beetles at Palacky University in the Czech Republic.
Light-producing beetles often have unusual adaptations. One of the most surprising is that females often look nothing like their male counterparts, instead retaining many larval features into adulthood.
“A good example of this is the trilobite beetle, where the females do not look like beetles at all, but superficially resemble trilobites. This means that the females are often overlooked when collecting in the field. We want to focus on these unusual beetles. in the search for the fossil record in the coming years, ”says Yan-Da Li.
The work has been published in the journal Proceedings of the Royal Society B.