Insects already had a variety of defense strategies in the Cretaceous

Early life stages of insects fulfill important functions in our ecosystems. They decompose dead bodies and wood, forming soil and returning various elements into material cycles. Not least, they are a major food source for many larger animals such as birds and mammals. This has led to many insect larvae developing structures and strategies for reducing the danger of being eaten. These include features like spines and hairs, but also camouflage and concealment. Over millions of years, a wide variety of such adaptation strategies have developed.

Researchers at LMU and the universities of Greifswald and Rostock have studied particularly well preserved fossils from Burmese amber and have been able to demonstrate that such anti-predator mechanisms had already evolved very diverse forms in insect larvae during the Cretaceous period 100 million years ago. This includes well-known strategies such as that employed by lacewing larvae, which carry various plant and animal materials on their back to give them camouflage, or the ploy of mimicking the appearance of certain plant parts.

"A particularly spectacular example is by far the oldest larva of a scorpionfly to have been discovered, which is the second fossil ever found to have special hairs on its back for attaching camouflage material," says Professor Carolin Haug, lead author of the article and zoologist at the Faculty of Biology. "Also, I could mention sawfly larvae that lived in leaves and created tunnels in them as they ate their way through the thin layer of the leaf interior." Overall, the article, which has been published in the journal iScience, shows that a large variety of different strategies already existed 100 million years ago for insect larvae to defend themselves against predators. "Observing the diversity of the past and the emergence and disappearance of various morphologies helps us better understand these processes, which is particularly important in view of the ongoing biodiversity crisis," says Haug.