The Kalligrammatid lacewings were large, butterfly-like insects that thrived during the Mesozoic Era, a time long before the emergence of modern butterflies. These fascinating creatures roamed through ancient Eurasian woodlands filled with ferns and cycads, becoming an integral part of the ecosystem that existed during the Jurassic and Cretaceous periods. Unfortunately, Kalligrammatid lacewings have been extinct for over 120 million years. However, through new fossil analyses, scientists at the Smithsonian’s National Museum of Natural History have uncovered surprising similarities between these ancient insects and modern butterflies, revealing that the Kalligrammatid lacewings may have shared traits with butterflies long before their time.
The discovery, led by Smithsonian paleoecologist Conrad Labandeira, was a breakthrough in our understanding of insect evolution. The team, made up of a diverse group of geochemists, botanists, entomologists, and paleobiologists, reported their findings in the prestigious journal Proceedings of the Royal Society B in early February 2023. Their research not only provides a deeper understanding of the Kalligrammatid lacewings but also highlights the phenomenon of convergent evolution—when two unrelated lineages evolve similar traits due to similar environmental pressures.
Kalligrammatid lacewings were relatively well-known among paleontologists, though their full ecological role remained a mystery for many years. These insects lived in Eurasia during the Mesozoic, a period dominated by the rise of dinosaurs, the first birds, and the early development of flowering plants. Despite being studied for over a century, the Kalligrammatid lacewings had remained enigmatic, with only limited information available about their behavior and interactions with the environment. This began to change with the discovery of exceptionally well-preserved fossils in northeastern China, specifically from regions that had once been vast lakes during the mid-Jurassic through early Cretaceous periods.
These ancient lakebeds, which were low in oxygen, provided ideal conditions for preserving delicate insect fossils with incredible detail, including features such as wings, proboscises, and other minute anatomical structures. These discoveries enabled Labandeira and his team to gain new insights into the structure and behavior of the Kalligrammatid lacewings, revealing a surprising number of similarities with their modern butterfly counterparts.
The key finding from the research was that Kalligrammatid lacewings had mouthparts that closely resembled the elongated, tubular proboscises of modern butterflies. These mouthparts suggested that the insects were feeding on fluids in a manner similar to modern butterflies. However, an important distinction emerged—while modern butterflies typically feed on nectar produced by flowering plants, Kalligrammatids lived in an era when flowering plants had not yet evolved. So, what were these ancient lacewings feeding on?
Paleobotanist David Dilcher, a member of the research team, suggested that the Kalligrammatid lacewings were likely feeding on sugary pollen drops produced by various Mesozoic seed plants. These insects may have played an essential role in pollination during the mid-Mesozoic, transferring pollen from one plant to another as they fed on these sugary drops. One of the primary food sources for the lacewings was likely bennettitaleans—an extinct group of plants that had long, tubular reproductive structures. The Kalligrammatid’s proboscis, capable of reaching into these deep structures, would have been perfectly suited to feed from these plants.
The study also examined the fossilized wings of the Kalligrammatid lacewings, revealing another striking feature—the presence of scales, similar to those found on the wings of modern butterflies. These scales, which contain pigments, likely gave the insects vibrant colors, adding an additional layer of similarity to their butterfly relatives. Further research into the patterns on the wings, particularly the eyespots, revealed additional clues about the evolutionary connections between the ancient lacewings and modern butterflies.
Eyespots, which are eye-like markings found on the wings of many butterfly species, are thought to have evolved as a defense mechanism to deter predators. The presence of eyespots on the wings of Kalligrammatids indicated that they too may have used this strategy to ward off potential threats. By comparing the chemical composition of the eyespots in both the Kalligrammatids and modern butterflies, the team discovered that both groups shared a similar pigment: melanin. This finding provided additional evidence that the genetic mechanisms responsible for eyespot formation had evolved much earlier than previously believed, dating back over 320 million years to the Paleozoic era.
What makes this discovery even more remarkable is that the similarities between Kalligrammatid lacewings and modern butterflies arose from two completely different evolutionary lineages. The last common ancestor of these two groups of insects existed more than 320 million years ago, and despite their divergence, both groups independently developed similar traits as a response to similar environmental pressures. This phenomenon, known as convergent evolution, is a striking example of how different organisms can evolve similar features when they occupy similar ecological niches or face comparable challenges.
In their analysis, Labandeira and his colleagues also pointed out that the relationship between Kalligrammatid lacewings and the plants they fed on likely played a significant role in the evolution of both groups. As the insects interacted with the plants, they would have influenced the plants’ reproductive success by transferring pollen, which in turn could have affected the plants’ evolutionary trajectory. This mutual relationship between pollinators and plants during the Mesozoic Era is an early example of the coevolutionary processes that we see in modern ecosystems today.
The study of Kalligrammatid lacewings also sheds light on the complex evolutionary dynamics that took place during the Mesozoic. The coevolution between these insects and their host plants likely created a dynamic feedback loop that shaped the development of both groups. In addition, the evolutionary pressure exerted by predators would have led to the development of defensive traits such as eyespots, which helped the lacewings evade being eaten. Together, these findings paint a picture of an intricate and evolving web of life in ancient Mesozoic woodlands, with interactions between insects, plants, and predators driving evolutionary change in ways that we are only beginning to fully understand.
As we look back at the findings of Labandeira and his team, it becomes clear that the Kalligrammatid lacewings represent an important chapter in the history of life on Earth. Their similarities to modern butterflies provide insight into the deep evolutionary history of insects and offer a glimpse into the complex ecological relationships that shaped the ecosystems of the Mesozoic Era. Moreover, the study highlights the powerful role that convergent evolution plays in shaping the traits of organisms in response to similar environmental pressures, a process that continues to influence the course of evolution in the modern world.
Through this detailed analysis of ancient fossils, scientists have not only deepened our understanding of extinct species but also illuminated the fascinating connections that link the past to the present. The discovery of the remarkable similarities between Kalligrammatid lacewings and modern butterflies exemplifies the ever-evolving nature of science, where each new finding builds upon previous knowledge to offer a more comprehensive understanding of life on Earth.
More information: Conrad C. Labandeira et al. The evolutionary convergence of mid-Mesozoic lacewings and Cenozoic butterflies, Proceedings of the Royal Society B: Biological Sciences (2016). DOI: 10.1098/rspb.2015.2893 , rspb.royalsocietypublishing.or … nt/283/1824/20152893