Dry rot species of fungi cause brown rot decay, preferentially removing cellulose and hemicellulose from the timber leaving a brittle matrix of modified lignin. The term "dry rot" is somewhat misleading, as both species of fungi "Serpula lacrymans" and "Meruliporia incrassata" require an elevated moisture content to initiate an attack on timber (28–30%). Once established, the fungi can remain active in timber with a moisture content of more than 20%. At relative humidities below 86 percent, growth of "Serpula lacrymans" is inhibited, but it can stay dormant at relative humidities down to 76 percent. These relative humidities correspond to equilibrium moisture contents
Serpula the mouth. While they are primarily feeding structures, the radioles also serve as respiratory organs. The radioles of different "Serpula" species are typically red, pink, or orange in color, with white transverse bands. Astaxanthin, a carotenoid pigment, is responsible for the bright red color of the crown of "S. vermicularis". There are usually about 40 radioles in an adult. One of these radioles, called an "operculum", is a highly specialized structure located on the dorsal part of the head. The operculum consists of a long, thick stalk with a cartilaginous, cone-shaped plug at the distal end. This plug can be