What was your last Halloween costume? What will your next costume be? Are you hungry? Well, you might think about being more practical with your costume, maybe keep it on all year and make sure it matches your food so it doesn’t see you coming. What, you know a better way to go about life? Ok, fine. Then you’re probably not a debris-carrying insect, and you’re definitely not a green lacewing larva on the hunt for wooly aphids for every meal. But you’re confused, right? Then keep reading.
There are lots of bugs that cover themselves in bits and bobs of material to camouflage from both predators and prey, and here you’ll read about this behavior that interested researchers who found fossils of these debris-carrying insects. These scientists focus on bark lice preserved in 100 million-year-old amber from Myanmar, and discuss debris-carrying overall as a camouflage behavior in insects. Examining fossils like this helps scientists understand the evolution of debris-carrying behavior as a way some insects modify their personal environment. Fossils are epic, but the bugs in them don’t do anything, so we’ll focus on the wacky behavior.
Debris-carrying is when a bug piles bits of things on itself and keeps them there. Most animals that decorate themselves with debris are arthropods, which include bugs, crabs, and spiders. In this paper, researchers discuss debris-carrying in insects multiple ways- they camouflage themselves from predators, and also prey by keeping the insect from being seen, or in the case of the lacewing larva I mentioned before, from being seen for who it is.
Debris-carrying behavior is just one strategy of camouflage- a method of modifying one’s environment to better its chances of getting something to eat and not getting eaten. Some other unique approaches to camouflage mentioned in the article are motion disguise in dragonflies, where they move their wings in a way that makes them appear perfectly still while in flight, or masquerade, when animals look like things that don’t move at all, like a stick insect that just looks like a stick.
So back to this fluffy larva: the green lacewing is a net-winged insect in the order neuroptera. As an adult, the green lacewing can fly away from anything that wants to eat it, but in its larval stage, it can’t fly away and must use the art of disguise for protection and to be sneaky to get food. Maybe the green lacewing larva disguises itself because it’s embarrassed that it’s body isn’t green like its name says it is. I’m just kidding! The protection and disguise to get food is the real goal here.
The lacewing larva eats tiny bugs, like the unlucky green-winged aphid you see in the picture. They have a special craving for woolly aphids, who resemble teensy tufts of cotton. Woolly aphids are often found together in clumps of white fluff. This fluff is called flocculent wax, and it is the debris carried by the lacewing larva into adulthood. The lacewing uses its mandible, a pair of piercing mouthparts, to impale its woolly prey. Then the larva bends its head up and back and sticks the waxy woolly aphid onto its back like a shovel. The larva does this again and again until it is piled high with waxy debris, which it carries on its body until it grows into a winged adult. And voila, we have a dashingly disguised debris-carrying green lacewing. The lacewing can’t keep this fluffy decor as an adult because it’s much too heavy to fly with. Plus, it can go a lot further a lot quicker to find food and make a breezy escape if it encounters a predator.
Alright, this behavior is pretty gruesome, but it also costs lots of time and energy for the larva. So why bother? Remember how the researchers explain this behavior as a camouflage tactic, it keeps the bugs from being eaten and helps them keep eating. A predator for the lacewing larva, such as an antagonizing ant, would choose to eat a naked lacewing over a debris-carrying one every time. The fun part for the lacewing, though, is that it can sneak up on those little woolly aphids living in their communal clumps. The lacewing doesn’t look like a predator to the aphids, so there’s no energetic cost for the lacewing to chase them down, so it just walks up to dine and that’s it. It’s fascinating- this insect takes time and effort to build itself a disguise on purpose and without any help on when, why and how to do it, and somehow knows it should do this behavior to succeed in life. Nature is amazing! Sadly for the aphid, up against a lacewing it will either become a decoration or dessert. Becoming prey is always a grim outcome in nature, but finding food is a do-or-die situation for predators too. The lacewings are eternally grateful for the wee aphids, and the wee aphids just as grateful to eat their leafy green snacks. For your next meal, take an extra second to thank the food on your plate and whoever put it there. Even more importantly, try and find some time to make yourself a silly hat out of something unexpected.
References
Kiesmüller C, Haug, JT, Müller P, Hörnig MK. 2021 Debris-carrying behaviour of bark lice immatures preserved in 100 million years old amber. PalZ, 96, 231–258. https://doi.org/10.1007/s12542-021-00567-6
2. Arthropods. San Diego Zoo Wildlife Alliance Animals and Plants. (n.d.). https://animals.sandiegozoo.org/animals/arthropods
3. Mizutani A, Chahl J, Srinivasan M. 2003 Motion camouflage in dragonflies. Nature 423, 604. https://doi.org/10.1038/423604a
