Paleontologists have found three lacewing larvae with large forward-directed stemmata (eyes in holometabolans) in 100-million-year-old Kachin amber from Myanmar. These specimens demonstrate the convergent evolution of highly developed simple eyes in at least two additional lineages of lacewings, showcasing the enormous diversity of lacewing larvae in the Cretaceous period.
Lacewing larvae from 100-million-year-old Kachin amber. Image credit: Haug et al., doi: 10.1111/1744-7917.13509.
Adult insects are known for their fascinating 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.
Yet some insect larvae are predators, and a small number of these have developed highly efficient imaging systems out of simple stemmata.
“The adults and pupae of holometabolan insects — beetles, bees, flies, butterflies, and their close relatives — have compound eyes, which are also present in a few larvae,” said Dr. Carolin Haug, a researcher at the Ludwig-Maximilians-Universität München, and her colleagues.
“In contrast, the larvae of most holometabolans have a small group of up to seven simple eyes, known as stemmata, on each side of the head.”
“Stemmata are unique to holometabolans, usually simple in structure, and are often oriented somewhat radially, yielding a wide field of view.”
“The visual fields of right and left stemmata rarely overlap, however, denying the larva binocular vision.”
“Furthermore, most stemmata lack a complex inner structure necessary for image formation.”
“Some predatory holometabolan larvae, in contrast, have evolved enlarged forwardly directed stemmata with overlapping fields of view facilitating binocular vision.”
“Examples include larvae of diving beetles, known as water tigers, tiger beetles, antlions, and whirligig beetles.”
“Stemmata have been reported in more than 120 fossil larvae, but in no case had image-forming eyes capable of binocular vision been identified.”
In new research, the authors discovered three predatory lacewing larvae with unusually large, forward-directed stemmata in Cretaceous Kachin amber.
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,” Dr. Haug said.
“The highly sophisticated simple eyes of predatory larvae evolved not only in antlions, water tigers, and tiger beetles, but at least a further twice convergently among extinct lacewing larvae.”
“Our results reveal a larger diversity of morphology, ecology, and feeding strategies among Cretaceous lacewing larvae than of those of today.”
The findings were published in the journal Insect Science.
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Carolin Haug et al. Cretaceous lacewing larvae with binocular vision demonstrate the convergent evolution of sophisticated simple eyes. Insect Science, published online February 18, 2025; doi: 10.1111/1744-7917.13509
