Adult insects are renowned for their highly specialized and intricate eyes, which grant them remarkable sensory abilities. These sophisticated eyes are essential for performing various life functions, including foraging for food, navigating their environments, and locating potential mates. However, insect larvae are a different matter entirely, as their eyes are often underdeveloped or absent during the early stages of their life cycle.
In many insect larvae, their visual needs are minimal, and simple eyes known as stemmata are typically sufficient. Stemmata are primitive, simple eyes that serve basic visual functions, helping larvae detect light and movement, primarily for orienting themselves in their surroundings. As PD Carolin Haug, a zoologist at the LMU Faculty of Biology, explains, “Stemmata are usually enough for these larvae, as they are primarily focused on eating and growing at this stage of life.” During this time, larvae are often little more than eating machines, consuming large amounts of food to fuel their growth and development into their adult forms.
However, not all larvae are purely consumers. A small number of insect larvae are predatory, requiring more advanced sensory tools to locate and capture their prey. Interestingly, a few of these predatory larvae have evolved specialized and highly efficient imaging systems, built upon the simple stemmata. Such specialized eyes have been discovered in modern insect larvae, particularly in species like antlions, tiger beetles, and water tigers, all of which are known for their predatory behavior and sophisticated hunting techniques.
Recent fossil discoveries, however, have provided even more intriguing evidence of the evolutionary development of complex visual systems in insect larvae. These findings suggest that the evolution of specialized eyes in larvae was not limited to the modern species mentioned above, but also occurred in ancient insect lineages. In fact, fossil records show that at least two other insect groups developed highly specialized visual systems during their larval stages, well before the advent of modern insects.
One of the key groups in this discovery are the lacewings, a group of insects closely related to antlions. Lacewings and their larvae were abundant and highly diverse during the Cretaceous period, the time when dinosaurs roamed the Earth. In a groundbreaking study, Carolin Haug and her research team discovered fossilized lacewing larvae that possessed highly specialized eyes similar to those of modern antlions. These fossils, preserved in amber around 100 million years ago, offer a fascinating glimpse into the evolutionary history of insect vision.
“Lacewings and their larvae exhibited astonishing diversity during the period of large dinosaurs, especially in the Cretaceous, which they subsequently no longer attained,” says Haug. This statement reflects the remarkable extent of the evolutionary innovation seen in lacewings during this era, with their larvae developing features that would later be lost in evolutionary history.
The preservation of the fossils in amber allowed Haug and her team to perform detailed investigations of the ancient larvae’s eyes. The team meticulously analyzed the size, shape, and orientation of the eyes and found striking similarities between the fossilized eyes and those of modern predatory larvae like antlions. Specifically, the eyes were positioned in a way that allowed for an optical resolution capable of detecting and tracking prey—critical capabilities for a predator. This discovery marks the first fossil evidence of such advanced visual systems in insect larvae, and as Haug points out, these eyes are the oldest known example of such sophisticated ocular structures.
These findings offer strong support for previous research that highlighted the incredible diversity of lacewings and other insect groups during the Cretaceous period. The discovery of specialized larval eyes in these ancient insects suggests that the evolution of complex visual systems in insect larvae was not a recent phenomenon but instead has deep evolutionary roots stretching back millions of years.
The study published in Insect Science provides new insights into the evolutionary history of insect vision and underscores the importance of fossil records in understanding the development of complex traits. The fossilized eyes of ancient lacewings offer not only a glimpse into the past but also reinforce the idea that insect larvae, particularly those of predatory species, have been honing their visual capabilities for millions of years to survive and thrive in their environments. These specialized eyes are an excellent example of how evolutionary pressures can shape the sensory systems of organisms, allowing them to adapt to their environments and improve their chances of survival.
More information: Carolin Haug et al, Cretaceous lacewing larvae with binocular vision demonstrate the convergent evolution of sophisticated simple eyes, Insect Science (2025). DOI: 10.1111/1744-7917.13509