by Janet Spencer
Come along with Tidbits as we look at how creatures construct architecture!
WORLD’S SMALLEST HOUSE
• An amoeba is a single-celled plant which moves around on the floor of a pond, engulfing food and consuming it. Some species of amoeba build themselves tiny houses out of sand grains, carrying them around like a snail in its shell. When the amoeba divides itself in half to propagate, its DNA is cut in half; its cytoplasm (which composes the main body) is divided in half; and the house goes with one half of the amoeba while a collection of unused sand particles contained within the cytoplasm goes with the other half. This is the smallest type of animal architecture ever discovered.
• One species of Central American moth is densely covered with long stiff hairs when it’s in the caterpillar stage. When it’s ready to pupate, it pulls out its hairs one by one with its jaws and then attaches the hairs to the stem of a plant using silk extruded from its mouth. Then it builds its cocoon in between rows of these spikey barriers, incorporating the last few hairs to strengthen the wall of the cocoon. In this way it’s protected from predators while it turns into a moth.
• The South American leafcutter ants build underground nests that go as deep as 18 feet (6 m) and house up to 8 million ants, not including 2 or 3 million larva and eggs. This is equivalent to the population of some of the biggest human cities, all living in a single structure. The ants earn their living by chewing the leaves of certain grasses to a pulp, and then cultivating an edible fungus from the pulp in chambers far underground. The fungus needs ventilation, and the ants build entrance holes in shallow mounds topped by tiny turrets made of dried mud. The wind is caught by the turrets and funneled into the depths of the ant colony.
• In the deciduous forests of the northern hemisphere, trees and other plants drop their leaves every autumn, thus ridding themselves of insect invasions. The insects need to start all over from scratch the following spring. But in the tropics, leaves are never dropped simultaneously, and therefore the trees and shrubs have developed other strategies of protection. One of the main methods is to use toxins in the foliage, making the leaves unpalatable or poisonous. The leaf cutter ants have gotten around this by using the fungus, which is unaffected by the toxins, and does not pass them on to the ants which thrive by eating the fungus.
• In South Africa, termite colonies build towers which average 6 feet tall. One was carbon dated and was about 5,000 years old, with the colony still thriving within.
• Long-abandoned nests of the mud dauber wasp found in caves in Western Australia. were carbon dated and found to be over 17,000 years old – remarkable for a delicate-looking nest made of mud. Mud daubers also build nests under bridges in the U.S. which are so sturdy that swallows use them as a foundation to build their own bird nests made of mud.
• Many people have spent their careers studying how a very large workforce of small-brained creatures can build a complex structure using very simple principles of organization. For instance, a nest of wasps was carefully studied by researchers who put colored dots on the backs of wasps in order to identify where they went and what they did. They found that there are four main tasks divided among the wasp colony: First was to forage for wood pulp; second was to bring water to the nest; third was to combine the pulp and the water and mix it to the right consistency to build the wasp nest; fourth was to forage for pollen and nectar for food.
• In small wasp colonies, task-switching was common, but in large colonies, very little task-switching occurred. In large colonies, when the nest was damaged so that more nest-building materials were required, squadrons of formerly inactive wasps would come forth to get the work done, but those wasps devoted to the gathering of food never joined in the ranks.
• Some species of moth and butterfly evolved to have detachable scales, so if they encounter a spider web, scales peel off and are left behind in the web while the bug falls free. Then spiders evolved to build longer webs so that as the insect falls, it runs out of detachable scales and becomes firmly stuck.
IT’S A FACT
• There’s a length of spider web 0.15 inches (4 mm) long caught and preserved in amber from Lebanon, which dates back to around 125 million years ago. It’s estimated that spiders have been on Earth for 400 million years, but this is the oldest piece of fossilized spider web found so far.
• A web will hold 4,000 times the spider’s weight.
• One species of rodent called the Brant’s whistling rat gets the blue ribbon for its tunneling ability. Most rodents who live underground will dig a burrow with one or two entrances. But this African rodent builds a system of branching tunnels with an average of 41 entrances, with some of them having over 500 places to exit. You might expect that such a complicated system of burrows would house dozens, if not hundreds, of rats. But the truth is that usually only one or two, sometimes three, rats live here. Why go through all the trouble? Because the Brant’s rat eats vegetation but lives in a desert where vegetation is sparse, and where cover from predators is hard to find. This way, the rat is never more than a short dash away from safety.
• Many species of spiders and caterpillars use silk for their own purposes, but it’s also scavenged and used second-hand by many birds. The tailor bird combines silk with soft and fuzzy plant down to make short lengths of yarn which is used to stitch together living leaves to make a pouch. The pouch is filled with grasses to form a nest.
• Grasses, palms, and lilies have veins that run parallel to each other, and they are called monocots. Trees, shrubs, and most flowers have veins that are more like lace, and they are called dicots. Birds that use plants for weaving nests prefer monocots. They clip a long blade of grass near the ground and fly off with it clutched in their beak, pulling a long narrow strip of leaf as the tear travels up between veins. They then have a nice long strong piece of thread. Researchers have shown that weaver birds use a variety of common knots, including half hitches, overhand knots, and slipknots, as well as over-and-under weaving used to construct the nest.