One of the most beautiful sights of summer twilight is the soft glow of fireflies illuminating the darkness of the twilight. These flickering insects are the most common bioluminescent insects, with approximately 2,500 species known worldwide. Their glowing bellies serve many purposes, but we don’t really have a good understanding of how this feature evolved.

A firefly perfectly preserved in golden yellow for years may have some answers, according to a team led by paleontologist Chenyang Tsai of the Chinese Academy of Sciences. About 99 million years ago Flammarionella hehaikuni it was already illuminating the dusk, showing that their ancestors had well and truly developed their characteristic shiny backsides in the Mesozoic.

This is the second Mesozoic firefly found in Myanmar amber. First, Protoluciola albertalleni There was also a perfectly preserved firefly lantern. A bioluminescent insect belonging to another family was also found in the same amber deposit.

What makes the new discovery so exciting is that the lantern-trapped sample differs from the lanterns seen in its amber-trapped contemporaries, suggesting that insect bioluminescence was already well-developed and diverse 99 million years ago.

Bioluminescence in fireflies appears to have two main functions: to attract other fireflies for courtship and to warn predators of any lucibufagin toxins they may be loaded with. However, scientists have recently claimed that bioluminescence appeared earlier in fireflies than in lucibufagins, raising some questions about the early advantages of insect bioluminescence.

Tsai and his colleagues found the fireflies in amber in Kachin State in northern Myanmar, the region where other Mesozoic insects originated.

The amber itself is extremely clear and reveals the insect in minute detail. Based on its physical characteristics, the researchers were able to identify the sample as a female belonging to the Luciolinae, one of the largest subfamilies of fireflies whose members have flashing lights on their abdomens.

However, there are some differences. antennas Flammarionella (named after French astronomer Camille Flammarion) is densely covered with hair-like processes called setae, with deep oval depressions in many segments.

Although we have never seen this feature in living fireflies, it is possible to encounter similar features in other insects. Pits associated with insect olfaction maximize surface area and aid in the recognition of sex pheromones. Male fireflies generally have more peculiar antennae than females of their own species; so look for the antennae of male fireflies. Flammarionella It will help us understand these features better.

The lantern in the fossil sample, which consists of two pieces at the end of the insect’s abdomen, is also striking. Hopefully, comparisons with other species of Mesozoic bioluminescent insects may be the subject of future studies. Meanwhile, the search for other fossilized fireflies and their relatives continues.

“As the fossil record expands in the future, we expect new discoveries that will expand our knowledge of when, how, and why bioluminescence evolved in these fascinating animals throughout the Mesozoic Era,” the researchers write in their paper.