Information about Termites (4)
Ecological and Economic Significance
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As decomposers termites feed on living or decaying wood. A major compound of wood is cellulose, a carbohydrate like starch. Breaking down cellulose requires an enzyme called cellulase. Some termite species have the ability to produce this enzyme, others live in mutualistic symbiosis with certain intestinal bacteria or protozoa, that provide the required cellulase. In order to cover their protein requirements, termites feed on fungi, growing on decaying wood. The importance of fungi for termites can be seen from the fact that a young queen on her colonising flight carries a bit of the fungi cake in her mouth. Once she settles down to found a new colony, she inoculates chewed wood with the fungus. Most termite species are harmless to timber and timber products, but others are even so hungry that they chew the plastic insulation of subterranean power and telephone cables.
Most termite species are utterly beneficial decomposers contributing towards a rapid recycling and turn-over of minerals. However, a handful of species are some of the most destructive pests of untreated timber products as well as of living standing trees causing, an economic loss of many millions of Kina every year. Characteristic of this group of insects are their chewing mouthparts and the ability to digest cellulose, the major component of wood. Termites chew and bore timber, causing either a considerable degrade of the material or resulting in the death of the host tree. Termites are social insects having three distinct castes, the reproductives (queen and king), the soldiers and workers. The colony can consist of more than a million individuals. The nest of a colony (termitarium) is located either underground (subterranean), on a tree (arboreal) or in a mound sticking out of the soil. Due to the unpigmented skin of most termites, they have to live in dark and moist conditions, protected from desiccation. Therefore the insects move only in the very long subterranean galleries or shelter tubes extending from their nest to gather food. Termites are sometimes difficult to identify and usually the soldiers are used for that purpose. Characteristic and thus helpful for identification is their nest type.
The most significant termite species in terms of economic loss are Microcerotermes biroi, Nasutitermes novarumhebridarium and Coptotermes elisae since all three species attack living trees of any age. They have the potential to kill their host within a few months, however in some cases the attack can take several years without any external symptoms, until the tree is thrown over by wind. Important is that termites usually only attack trees that are somehow weakened or otherwise under stress. Weakened trees release a volatile chemical (kairomone) which is used by the termites to locate the diseased tree. Once attacked by termites, the tree is quite helpless, because its natural immune system or resistance is decreased and pests can not longer be defeated effectively. The symptoms of termite infestations are more or less conspicuous and obvious, however in some cases an apparently healthy tree suddenly dies without having shown any external signs.
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© Michael F. Schneider, 1999