Insect larvae developed camouflage 110 million years ago
A recently discovered new species of insect larva with its specialized pack of plant remains indicates that a complex camouflage behavior used by insects today dates to at least 110 million years ago.
The discovery by a team of Spanish researchers and Michael S. Engel, a KU Biodiversity Institute entomologist and professor of ecology and evolutionary biology, was based on the study of an amber piece found in 2008 in the El Soplao outcrop (Cantabria, Northern Spain), the Mesozoic’s richest and largest amber site in Europe. The study is being published this week in the prestigious Proceedings of the National Academy of Sciences (PNAS).
The fossil, about four millimeters long, is a predatory larva of the order Neuroptera (lacewings and their relatives). It is covered by a tangle of plant filaments that it collected with its jaws to form a defensive shield and camouflage itself. This survival strategy, sometimes called “trash carrying,” is observed in current species to render them nearly undetectable to predators and prey.
Related to current green lacewings, the fossil represents a new genus and species designated Hallucinochrysa diogenesi. The name alludes to its “mind-blowing appearance,” the researchers said, and its resemblance to Diogenes syndrome, a human behavioral disorder characterized by compulsive hoarding of trash.
The research identified the filamentous plant remains composing the larval trash packet as trichomes, or plant hairs with diverse shapes and functions. The trichomes are thought to belong to a specific group of ancient ferns.
Today green lacewing larvae harvest plant materials or even detritus and arthropod remains and carry them on their backs, nestled among small tubercles with hairs. On the contrary, Hallucinochrysa diogenesi possessed a bizarre characteristic: it possessed extremely elongate tubercles, with hairs that had trumpet-shaped endings acting as anchoring points. All this structure, completely unknown until now, formed a dorsal basket that retained the trash and prevented it from sliding when the insect moved.
Hallucinochrysa diogenesi demonstrates that camouflage strategy and its necessary morphological adaptations appeared early and was well developed during the era of the dinosaurs. In the case of green lacewings, this complex behavior has been around for at least 110 million years. This is significant for evolutionary studies pertaining to animal behavior and the adaptative strategies of organisms throughout Earth’s history.
The study also shows an ancient and close plant-insect interaction — possibly an example of mutualism: the predatory larvae saved ferns from plagues, whereas ferns provided larvae with a habitat and protection. In a Cretaceous environment where resin forests in the ancient Iberian Peninsula were razed by wildfires, this larva collected remains from a fern that grew abundantly after wildfires.
The El Soplao outcrop, where the discovery was made, is one of the most important localities aiding researchers to unravel questions about Earth history, ancient forest ecosystems, and the evolution of major invertebrates lineages such as the insects.
In addition to Engel, the researchers who participated in the study are: Ricardo Pérez-de la Fuente and Xavier Delclòs, of the University of Barcelona (Spain); Enrique Peñalver, from the Geomineral Museum in Madrid; and Mariela Speranza, Carmen Ascaso and Jacek Wierzchos, from the National Museum of Natural Sciences of the Spanish National Research Council.