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 just behind the head. There is a median, longitudinal, ciliated, thoracic fecal groove on the dorsal midline of the thorax. It is a broad, shallow, relatively indistinct trough running the length of the thorax and ending at the head. Worms of the genus "Serpula" have a distinct abdominal region, composed of up to 190 very short, wide segments. The terminal body region is the tiny pygidium, on which the anus is located. A fecal groove extends the length of the ventral midline of the abdomen. The fecal groove spirals across to the dorsal position as it reaches the thoracic region.