The capacity of insects to perceive environmental cues and transmit information constitutes a critical foundation for their remarkable evolutionary success and extraordinary taxonomic diversity on Earth. Over their long evolutionary history, insects have evolved sophisticated sensory organs and diverse signal communication strategies, relying on chemical odours, acoustic signals, colour patterns and bioluminescence for interindividual signalling. Nevertheless, direct fossil evidence documenting the origin and evolutionary trajectories of these intricate sensory and communication systems, as well as the interplay between distinct signalling modalities, remains scarce, given the extremely low preservation potential of soft tissues and delicate microstructures.
Recently, LI Yanda, a PhD student at the University of Bristol, together with Professor CAI Chenyang from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), and co-authors described a distinctive new genus of lampyroid beetles from mid-Cretaceous Kachin amber of Myanmar. Phylogenetic analyses indicate that the new genus, Icaroramus, likely belongs to the extinct family Cretophengodidae. The fossil specimen preserves elaborate antennae alongside fully intact abdominal light-emitting organs. The co-occurrence of these two diagnostic traits in a single fossil individual provides pivotal evidence for reconstructing the early evolution of sensory and signalling systems in fireflies and their close relatives. This research was published in Proceedings of the Royal Society B.
The most striking morphological trait of Icaroramus lies in its unique antennae. The antennae consist of twelve segments; antennomeres 4 to 11 each bear two pairs of lateral rami with disparate morphologies. The proximal pair of rami at the base of each antennomere is elongated with dilated apices and coarse setae, whereas the medial pair near the segment midpoint is shorter, slender and covered only with fine hairs. Such heteroramose antennae—characterised by two morphologically distinct pairs of lateral branches on a single antennomere—are unprecedented across the entire Coleoptera order. From a developmental evolutionary perspective, this specialised antennal morphology may arise from partial reactivation of the antennal segmentation programme within individual antennomeres, generating extra branching outgrowths.
Numerous extant insect lineages that locate mates via chemical communication possess well-developed branched antennae to enhance detection of trace airborne pheromones. The highly complex ramified antennae of Icaroramus imply that this extinct lampyroid probably relied heavily on pheromonal cues during mate searching. Furthermore, the clear morphological differentiation between the two sets of antennal rami may reflect functional partitioning of olfactory sensilla, enabling the beetle to discriminate between distinct chemical signals. Such highly specialised chemosensory capacity demonstrates that Cretaceous lampyroids had evolved sophisticated ecological adaptations.
By contrast, the exact biological function of the abdominal photic organs cannot be definitively resolved solely from fossil material. Extant firefly clades that use light signals for courtship generally exhibit simplified antennae, yet Icaroramus combines elaborate light organs with highly branched antennae—a trait combination inconsistent with most modern fireflies dependent on luminous mating signals. Accordingly, the bioluminescent organs of Icaroramus most likely functioned for aposematic anti-predator defence, though a supplementary role in mate attraction cannot be entirely ruled out.
Collectively, Icaroramus reveals that lampyroid beetles already possessed both highly specialised sensory structures and functional bioluminescence by the Cretaceous (~100 Ma), offering novel fossil insights into the evolutionary origins of the complex signalling machinery of fireflies.
This work was supported by the National Key Research and Development Program of China. Reconstruction illustrations were created by illustrator Dinghua Yang.
Reference: Li, Y.-D., Kundrata, R., Huang, D., Tin Aung Myint & Cai, C. (2026) A firefly relative that smelled and glowed: evidence for complex signalling systems in Cretaceous lampyroids. Proceedings of the Royal Society B, 293, 20260295. https://doi.org/10.1098/rspb.2026.0295.
Fig.1 Icaroramus perisi and its unique heteroramose antennae
Fig.2 Phylogenetic tree showing the systematic placement of the genus Icaroramus
Fig.3 Ecological reconstruction illustrating luminous Icaroramus in a Cretaceous forest
Download：