some materials in nature act as ready made "building blocks" to the animals in question, such as feathers and leaf petioles for some birds and animal hair for the chaffinch. other materials need to be "processed". caddisfly larvae use stone pieces and also cut sections from green leaves for use in construction. the stone pieces are selected as per their size and shape from a large variety. in the case of leaf sections, these are cut and shaped to required size. similarly bagworms cut and shape thorns or twigs to form their case. some sphecid wasps collect mud and blend them with water to construct free standing nests of mud. paper wasp queens build with paper pulp which they prepare by rasping wood with their jaws and mixing with saliva, a case of collecting, processing and blending raw materials.