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Fossil study reveals oldest larval eyes with high-resolution vision

Adult insects are known for their fascinating and complex eyes, which allow them to accomplish remarkable sensory feats when performing functions such as searching for food or mates. In many insect larvae, however, these eyes have not yet developed.

"Simple eyes, known as stemmata, are usually sufficient for these larvae, as they are often just little eating machines at this stage of life," explains PD Carolin Haug, zoologist at LMU's Faculty of Biology.

Yet some insect larvae are predators, and a small number of these have developed highly efficient imaging systems out of simple stemmata. At least three instances of this have been found in modern insect larvae: in antlions, tiger beetles, and water tigers.

New fossil finds reveal that insect larvae developed such highly specialized eyes during evolutionary history in at least two further cases. This occurred among the larvae of distant relatives of antlions—that is to say, lacewings. An expert in fossil insect larvae, Haug made this discovery together with her research team. The were recently published in the journal Insect Science.

"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.

The fossils were preserved in amber about 100 million years ago, which allowed the team to conduct detailed investigations and measurements. They found that the size and orientation of the larval eyes are comparable to those of modern antlions and enable similar optical resolution.

"This is the first fossil evidence, and thus the oldest, of such eyes," says Haug. The findings support earlier work which had shown that lacewings were characterized by extraordinary diversity during the Cretaceous period.