form sticky traps for prey, or it may be processed, as in the case of salivary excretion used for creation of paper by paper wasps, by blending it directly with wood pulp. Self-secreted materials may be processed in some cases. In cribellate spiders, silk produced by the spider are reworked in the cribellum to form fine sticky strands used for capturing prey. In other cases, the scale wax, produced on the bodies of honey bees, is gathered and blended with saliva, to form comb wax, the building material. Not all self-secreted materials are developed specifically for that purpose. For example, bird feathers are used for lining and insulation, a typical example being that of the female common eider duck (Somateria mollissima), which produces down feathers for lining its nest. Cocoons are another type of structure formed to protect the organism from predation. In order to transform from a larva into a butterfly or moth, a caterpillar must undergo drastic changes in its body. These changes require significant amounts of energy and occur over long periods of time, making a caterpillar very vulnerable to predation. To overcome this, caterpillars will produce silk to form a cocoon or pupa, a structure in which the caterpillar will reside while pupating to lower its risk of predation. Some species of caterpillar, such as the silkworm (Bombyx mori) are able to spin multiple cocoons in the event that one gets destroyed. Other caterpillars will even form defensive structures to accompany their pupas. The Aethria carnicauda caterpillar uses the hairs that cover its body as a defensive mechanism against predators. When it is time to form a cocoon, the caterpillar rips the hairs off of its body and places them around the pupating site. This creates a series of defensive walls to protect the vulnerable caterpillar while resides in its cocoon. Evolutionary consequences Recently, some researchers have argued that the structures built by animals affect the evolution of the constructor, a phenomenon known as niche construction. See also Tool use by animals Nest-building in primates References Ethology