Isoptera modern lower termites (Kalotermitidae and Prorhinotermes of Rhinotermitidae) The Termopsidae usually nest in large damp wood and are called damp wood termites, while the Kalotermitidae usually nest in dry wood of living and fallen trees and are called dry wood termites Prorhinotermes of the Rhinotermitidae nest in ordinary wood In the one-piece type, the size, growth, and longevity of the colony are constrained by the size of a wood piece The intermediate type is observed in primitive lower termites (Mastotermitidae) and the modern lower termites (most Rhinotermitidae) The separate type is observed in primitive lower termites (Hodotermitidae), modern lower termites (a few Rhinotermitidae), and the higher termites (Termitidae) Separate type nests are classified into three categories: (a) Figure A chimpanzee fishing termites with a stick in a fungus-growing termite mound Reproduced from Behnke FL (1977) A Natural History of Termites New York: Charles Scribner’s Sons Figure Nests of Nasutitermes triodiae in Australia 415 subterranean nests constructed below ground, (b) epigeous nests protruding above soil surface, and (c) arboreal nests built on a tree trunk or a tree branch but always linked with soil by covered galleries Symbiosis Digestive Tube Termite symbiosis is an obligate nutritional mutualism between the termite and microorganisms in the gut and nest of termites, although symbiosis, in the general sense, means the living together of two or more organisms that are not closely related in phylogeny, without the implication of beneficial exchanges The digestive organ of lower termites is schematically shown in Figure The digestive tube consists of foregut, midgut tubular (site for secretion of digestive enzymes and for absorption of soluble nutrients), and hindgut (voluminous site for digestion and for absorption of nutrients) The swollen portion of the hindgut is called the paunch Malpighian tubules, which transport urine and urinary metabolites for excretion, empty at or near the junction of mid- and hindgut Midgut and salivary glands produce the enzyme for decomposing cellulose into glucose In the hindgut, cellulose is decomposed into acetic acid by symbiotic flagellates The microenvironment becomes more anoxic from foregut to hindgut The hindgut used to be considered an anaerobic fermentation chamber, but recently this has been found to be false The hindgut consists of an anoxic lumen surrounded by a microoxic periphery (Figure 9) This is consistent with the occurrence of both anaerobic and O2-dependent microbial metabolism in the hindgut Bacteria on or near the gut wall constitute an oxygen sink, consuming the inwardly diffusing O2 and thereby creating anoxic conditions favorable for