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 vermicularis tube is fabricated by the glandular ventral shields on the other thoracic segments, where calcium is mixed with an organic secretion to make a paste. This is formed into shape by a collar found just behind the first segment, the prostomium. "Serpula vermicularis" is a filter feeder and extends its radioles to catch phytoplankton and detritus. The radioles also act as gills. Blood is pumped in and out of these with the flow direction alternating in a single set of vessels. The blood is then pumped through a ventral blood vessel to the tip of the abdomen before returning through