Animals have evolved complex survival strategies to suit the demands of their habitats. Through these changes, some have become excellent architects. They work with the environment to meet their needs, including for protection and prey.
Caddisfly larvae with cases, from left, made of pebbles, twigs and assorted debris (Jim Rathert/Missouri Department of Conservation)
By Ethan Hatchett
Many items are discarded in the natural world. Leaves fall, branches break and, sadly, animals die. But some creatures profit from this refuse. For these collectors, others’ trash can be their treasure.
Take the case-building caddisfly, which lives in freshwater ecosystems across Georgia. Its larvae resemble caterpillars and feed on algae, aquatic vegetation and microfauna in the water. But even more novel, they create casings from objects they find.
In its larval stage, the caddisfly has a unique ability to spin silk underwater. The insect uses this sticky silk to create its case. The case then serves as a suit of armor that protects the creature’s fleshy abdomen from predators. As for the armor pieces, the caddisfly larva takes advantage of its surroundings, using empty snail shells, sand, rocks and other material to fortify itself.
Case-building caddisflies belong to the order Trichoptera, which includes many species. These caddisflies are well adapted to survive underwater. But their success hinges on their ability to spin silk and the ease with which they then create cases out of available material.
Disguise + food = adult lacewing (UF/IFAS, Katherine Taylor/University of Maryland, Alan Cressler)
The larvae undergo a complete metamorphosis. Adult caddisflies resemble moths and only live for about a month. Most don’t even feed as adults. Individual species can be difficult to identify as adults, and most are identified as their more distinct larvae.
Green lacewing larvae (right) use discarded material in a different but no less effective way.
The young of these insects spend their lives among vegetation throughout the state, preying on soft-bodied insects such as aphids. Yet instead of creating makeshift armor like the caddisfly larva does, the larval lacewing uses bits of organic matter and the carcasses of its prey as a disguise.
The species has earned the nickname trash bug (watch) for its interesting disguises.
The larva has bristles on its abdomen that allow debris to stick to it. The disguise serves two purposes: camouflage from predators and subterfuge for hunting. By utilizing debris, the trash bug can slip unnoticed among its favorite prey.
The lacewing larva undergoes a complete metamorphosis into an adult green lacewing. These insects belong to the family Chrysopidae, which includes species common in North America and Europe. Most adults feed on pollen, honeydew and nectar, but some species also feed on insects.
Lacewing larvae are one the most beneficial animals to have in your garden. Their ferocious appetite has also earned them nicknames. One is the aphid wolf.
Collecting objects that would otherwise decay offers many advantages. The material can provide protection and also double a disguise to get closer to prey. And while opportunistically using whatever they can find to build their structures, these animals create a testament to their ingenuity and their daily struggle for survival.
Next up in Animal Architects: Producers make structures using materials from an unusual source – their bodies. Also read about Excavation Experts and Farmers in this Georgia Wildlife blog series.
Ethan Hatchett is a communications assistant in agency’s Wildlife Conservation Section.