Animals have evolved complex survival strategies to suit the demands of their habitats. Through these changes, many have become excellent architects, even developing products that are truly homemade.
By Ethan Hatchett
Eastern tent caterpillars on the move (USFWS)
Some animals help create their ideal environments by using material created from their bodies. This ability allows many of what we’ll call producers to flourish and become more widespread, while for others with this special skill it can lead to them becoming more scarce because of their specific habitat requirements.
One of the most prolific and widespread producers is the eastern tent caterpillar. This caterpillar can be found on deciduous trees all over Georgia in early spring. The insect is brightly colored and covered with soft hair-like setae. Although usually regarded as a pest, there is more to this moth-to-be than meets the eye.
The eastern tent caterpillar is one of the most social caterpillars. Hundreds of individual worms work together to create a home, stay warm and forage for food. The caterpillars even communicate with each other using scents (not unlike ants).
Tent caterpillars make their home in elaborate tents made of silk stretched between branches and shared with their siblings. After hatching from their egg mass, the tiny caterpillars spin a small tent using silk produced from their bodies. As the caterpillars grow, they add layers of silk to the tent. The tent serves three distinct purposes: as insulation, protection from predators and a homebase (watch).
The silk structure acts as a greenhouse, trapping heat between its many layers. The caterpillars bask in the sunlight or – on colder days – crawl deeper inside the layers to stay warm. Conversely, when they get too hot, the caterpillars can move to a shaded area of the tent. The added humidity from the layers helps with the molting process as the insects grow.
The tough silken strands also shield the caterpillars nestled inside from predators. Birds, lizards, chipmunks and other predators have a harder time catching individual worms when they are buried in silk. Most predators eat the insects either when they leave the nest to create cocoons or have already transformed into moths
Eastern tent caterpillars will stray from the safety of the tent to eat foliage. The silken nest acts as a base to launch group feeding forays as well as a safe place to return. When on foraging expeditions, the caterpillars will leave silk trails so they can find their way back.While tent caterpillars can be a serious pest for orchards, their populations are cyclical. While high one year, they will not be the next year.
The cellophane bee is a less social but no less talented producer. Found in pockets throughout Georgia and usually nesting in patches of soil with little to no vegetation, this family of bees can be very particular about habitat, preferring specific plants to pollinate and choosing to nest only in certain soils (also see: “Uncommon Bee at Alligator Creek“).
Southeastern sandhill cellophane bee, one of the cellophane bees in Georgia (Dave Almquist/Florida Natural Areas Inventory)
Their nests are as unique. Female cellophane bees create homes in the ground by digging a short tunnel and producing a protected cell for each egg. However, the eggs are vulnerable to soil-borne fungi encouraged by underground moisture. To combat this threat, the bees add a protective waterproof seal.
How? First, the female bee uses her paint-brush-like forked tongue to smear saliva over the nest’s walls. Then, using the Dufour gland on her abdomen, she spreads another liquid on the walls. When these liquids mix it produces a cellophane-like structure not unlike a plastic bag. After creating the bag, she uses a gland in her mandibles to spray the walls again with a liquid that is both antimicrobial and antifungal. After all of that hard work, the bee suspends the incased egg using more cellophane on the tunnel wall or ceiling to further minimize exposure to moisture. She then seals the nest entrance from the outside world (watch).
Cellophane bee nests (University of Wisconsin)
Cellophane bees leave food in the nest for when their offspring hatch. Most ground-dwelling native bee species create a “bread loaf” from pollen and nectar. But cellophane bees have another specialized approach to rearing young. Before sealing the nest, the female leaves a liquid meal or “soup” of pollen and nectar for her unhatched egg. When the egg hatches, the newly emerged bee falls into its first meal and begins eating.
While cellophane bees are solitary, they don’t mind clustering their nests together (watch). People can be frightened by seeing several bees flying around a patch of dirt, but don’t fret. Cellophane bees are not aggressive. They have no instinct to protect the hive so they will not bother any wayward or curious humans.
In fact, some scientists have been studying cellophane bees in hopes of finding a natural alternative to plastics. The bees could be key to reducing waste in the future.
Being able to create structures from their bodies affords producers many advantages. One of the most critical is that it makes them more self-sufficient, needing less from other sources to meet tasks that help them survive.
Next up in Animal Architects: These animals use other organisms in a familiar but intriguing way. Also read about Excavation Experts and Collectors in this Georgia Wildlife blog series.
Ethan Hatchett is a communications assistant in DNR’s Wildlife Conservation Section.