Crafty camouflage

Last week we brought you snails that attach all manner of pebbles, fossils, corals and shark teeth to their shells. Today we give you a newly-discovered fossil green lacewing larva that attached pieces of soil to its body as an act of camouflage. Our research fellow Ricardo Pérez-de la Fuente, lead author of the new paper, explains…

Visual camouflage is one of the most successful survival strategies in nature. Camouflaging is usually defensive, allowing animals to be left unnoticed by their predators, but it can also be used aggressively by predators themselves to approach their prey undetected.

Some camouflaging animals can actively change their colouring to match that of the background ‒ a technique called crypsis. Others can make their bodies resemble elements of the environment, such as leaves or twigs, which is called mimicry.

Yet another approach to camouflage involves collecting diverse materials from the environment and incorporating them on the animals’ bodies in order to better blend with the surroundings. This is known as debris-carrying, trash-carrying, or decoration, and it can be found across a wide variety of animals including sea urchins, gastropods, and arthropods, such as decorating crabs, or sand- and mud-covering spiders.

My colleagues and I have just published the discovery of a fossil green lacewing larva, pictured at the top of the article, that has been preserved carrying bits of soil that it used for camouflage and physical protection. It’s a new larval species just 1.5 mm in length, and is preserved in Early Cretaceous Lebanese amber. We have named it Tyruschrysa melqart after the Phoenician city of Tyre and its tutelary god Milk-Qart (if you want to learn the reasons behind this name check out our open access paper!).

Green lacewing larvae are active predators that eat other insects such as aphids, using sickle-shaped ‘jaws’ to pierce their prey, suck out their fluids and liquefy their tissues; eating is easier when there is no need to chew! Some green lacewing larvae are debris carriers, entangling all kinds of debris among their velcro-like ‘hairs’ called setae, which extend from relatively short ‘bumps’ on their backs. This debris is carefully selected and gathered with meticulous head and body movements to form a so-called debris packet on the back of the insect.

The new fossil and similar ones described from younger Cretaceous ambers differ from modern relatives because instead of short ‘bumps’ with setae on their backs they have relatively long ‘tubes’, giving them a bizarre appearance.

These tubes have setae with mushroom-shaped endings of a kind never seen before in extinct or living green lacewing larva species. The mushroom-shaped ending is a special adaptation to anchor debris, which in the case of Tyruschrysa melqart are fragments of soil.

It was already known that Cretaceous green lacewing larvae like Tyruschrysa had long tubes on their backs and that they collected plant hairs and other plant material to construct their packet of debris. But thanks to the new discovery we now know that these immature insects also used bits of soil, and that in the deep past debris packets were probably as diverse as those we see today.

Green lacewing larvae have been gathering debris to camouflage and protect themselves for about 130 million years, giving rise to the different body adaptations we see amongst these fascinating tiny collectors.

‘A soil-carrying lacewing larva in Early Cretaceous Lebanese amber’ Ricardo Pérez-de la Fuente, Enrique Peñalver, Dany Azar and Michael S. Engel is published as open access in Scientific Reports this month.