The Web of Life (126-10) Construction


The building of structures by animals is ubiquitous. ~ American zoologist Scott Turner

Animals are not the only home builders. Construction has an ancient lineage going back billions of years.

Some bacteria create calcified shells for protection. One seaborne cyanobacterium builds an internal skeleton as a ballast assist.

The bacterium that causes Legionnaires’ disease hides from its host cell immune system by building a vacuole (bubble) in which the bacterium resides. The bacterium jiggers host proteins to divert raw materials for the construction project.

The bacterial proteins use the cellular membrane proteins to build their house, which is like a balloon: it needs to stretch and grow bigger as more bacterial replication occurs. The membrane material helps the vacuole be more rubbery and stretchy, and also camouflages the structure. The bacteria are stealing material from the cell to build their own house and disguising it so that it blends in with the neighborhood. ~ Chinese biologist Zhao-Qing Luo

Protozoa build protective shells (termed tests) by secreting material from their cell surface. For fortification, the marsh-dwelling amoebozoa Difflugia adds swallowed sand to its shell. During budding or fission, material is passed into the daughter, where it is joined by organic cement. The result resembles a tiny croquette.

Plants are the consummate constructors. Once established on land, their lush, verdant municipalities beckoned arthropods, the pioneer land animals.

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Bristle worms are ancient segmented sea worms that have adapted to extreme ecological niches: some living in the coldest ocean abyssal plain, while others tolerate the heat of hydrothermal vents. Bristle worms on the ocean floor burrow.

Crabs dig burrows too. Some fiddler crabs add hoods to their burrow entrance as an adornment to attract females for courting.

Numerous fish species build nests to shelter their eggs, including the large freshwater frankfish, which uses floating vegetation to form a corridor leading to a cul-de-sac end where eggs are laid.

Octopi are often home builders, improving chosen rock crevices that serve as shelter; excavating the cavity by removing sand and stones; bringing stones, shells, molted crab claws, and other ornaments, even bottles, to partly block the entrance.


Small, moth-like caddisflies got their start in the Triassic period, over 200 million years ago. Now there are 12,000 known species.

Adults live but 1 to 2 weeks, having spent weeks, or even months, in a freshwater pupa stage. As larvae, they wrap themselves in cases from selectively cut materials, held together by secreted silk.

Larvae scurry on the sandy bottom of the water body where they live, collecting material. Sometimes a larva will take over an empty case, adapting it as it sees fit. An abode is supplemented as a larva grows.

Caddisfly case construction reflects a larva’s personality. Different larvae have decided preferences for different materials, whether plant stems or tiny pebbles.

Caddisfly larvae have a specific sense of how they like their home to look. If the jagged contour of an outer edge is smoothed away by a pesky human researcher, a larva straightaway acts to rectify the intrusion: collecting fresh material and cutting it just so before gluing it into place to cover the defect.

One caddisfly, Macronema transversum, builds an elaborate chambered case, with well-ventilated flow, and a mesh net to catch food. In its complexity, M. transversum‘s creations rival the nests of many birds.

These insect larvae thus exhibit a considerable degree of versatility, not only in the initial construction of their cases, but in repairing them. ~ Donald Griffin


Disparate insects construct a tremendous variety of nests or shelters. Wasps, hornets, bees, and termites are the best known.

Ant colonies are elaborate structures. Ants are also able to improvise in their constructions.

Facing a flood, ants build rafts, using both the buoyancy of the brood and the recovery ability of workers to minimize injury or death. Workers protect the queen by placing her in the center of the raft. Conversely, the youngest colony members, which are considered the most expendable, are put in the most vulnerable positions. The brood are most buoyant, and so they form the base of a raft.