Timber damage
Due to their wood-eating habits, many termite species can do great damage to unprotected buildings and other wooden structures. Their habit of remaining concealed often results in their presence being undetected until the timbers are severely damaged and exhibit surface changes. Once termites have entered a building, they do not limit themselves to wood; they also damage paper, cloth, carpets, and other cellulosic materials. Particles taken from soft plastics, plaster, rubber, and sealants such as silicone rubber and acrylics are often employed in construction.
Humans have moved many wood-eating species between continents, but have also caused drastic population decline in others through habitat loss and pesticide application.
Precautions:
- Avoid contact of susceptible timber with ground by using termite-resistant concrete, steel, or masonry foundation with appropriate barriers. Even so, termites are able to bridge these with shelter tubes, and it has been known for termites to chew through piping made of soft plastics and even some metals, such as lead, to exploit moisture. In general, new buildings should be constructed with embedded physical termite barriers so that there are no easy means for termites to gain concealed entry. While barriers of poisoned soil, so called termite pre-treatment, have been in general use since the 1970s, it is preferable that these be used only for existing buildings without effective physical barriers.
- The intent of termite barriers (whether physical, poisoned soil, or some of the new poisoned plastics) is to prevent the termites from gaining unseen access to structures. In most instances, termites attempting to enter a barriered building will be forced into the less favourable approach of building shelter tubes up the outside walls, and thus, they can be clearly visible both to the building occupants and a range of predators. Regular inspection by a competent (trained and experienced) inspector is the best defence.
- Timber treatment.
- Use of timber that is naturally resistant to termites such as Syncarpia glomulifera (Turpentine Tree), Callitris glaucophylla (White Cypress), or one of the Sequoias. Note that there is no tree species whose every individual tree yields only timbers that are immune to termite damage, so that even with well known termite-resistant timber types, there will occasionally be pieces that are attacked.
When termites have already penetrated a building, the first action is usually to destroy the colony with insecticides before removing the termites' means of access and fixing the problems that encouraged them in the first place. Baits (feeder stations) with small quantities of disruptive insect hormones or other very slow acting toxins have become the preferred least-toxic management tool in most western countries. This has replaced the dusting of toxins direct into termite tunnels that had been widely done since the early 1930s (originating in Australia). The main dust toxicants have been the inorganic metallic poison arsenic trioxide, insect growth regulators (hormones) such as triflumuron and, more recently fipronil, a phenyl-pyrazole. Blowing dusts into termite workings is a highly skilled process. All these slow-acting poisons can be distributed by the workers for hours or weeks before any symptoms occur and are capable of destroying the entire colony. More modern variations include chlorfluazuron, diflubenzuron, hexaflumuron, and novaflumuron as bait toxicants and fipronil and imidacloprid as soil poisons. Soil poisons are the least-preferred method of control as this requires much larger doses of toxin and results in uncontrollable release to the environment.
Termites in the human diet
In many cultures, termites are used for food (particularly the alates). The alates are nutritious, having a good store of fat and protein, and are palatable in most species with a nutty flavour when cooked. They are easily gathered at the beginning of the rainy season in West, Central and Southern Africa when they swarm, as they are attracted to lights and can be gathered up when they land on nets put up around a lamp. The wings are shed and can be removed by a technique similar to winnowing. They are best gently roasted on a hot plate or lightly fried until slightly crisp; oil is not usually needed since their bodies are naturally high in oil. Traditionally they make a welcome treat at the beginning of the rainy season when livestock is lean, new crops have not yet produced food, and stored produce from the previous growing season is running low.[citation needed]
They are also eaten in Indonesia, including Central Java, where they are roasted or fried.[citation needed]
Agriculture
Termites can be major agricultural pests, particularly in Africa and Asia, where crop losses can be severe. Counterbalancing this is the greatly improved water infiltration where termite tunnels in the soil allow rainwater to soak in deeply and help reduce runoff and consequent soil erosion.
Building materials
Termite nests are used widely in construction (the dirt is often dust-free) and as a soil amendment.[citation needed]
Termites as a source of power
The US Department of Energy is researching ways to replace fossil fuels with renewable sources of cleaner energy, and termites are considered a possible way to reach this goal through metagenomics.[8]
Termites may produce up to two litres of hydrogen from digesting a single sheet of paper, making them one of the planet's most efficient bioreactors.[9] Termites achieve this high degree of efficiency by exploiting the metabolic capabilities of about 200 different species of microbes that inhabit their hindguts. The microbial community in the termite gut efficiently manufactures large quantities of hydrogen; the complex lignocellulose polymers within wood are broken down into simple sugars by fermenting bacteria in the termite's gut, using enzymes that produce hydrogen as a byproduct. A second wave of bacteria uses the simple sugars and hydrogen to make the acetate the termite requires for energy. By sequencing the termite's microbial community, the DOE hopes to get a better understanding of these biochemical pathways. If it can be determined which enzymes are used to create hydrogen, and which genes produce them, this process could potentially be scaled up with bioreactors to generate hydrogen from woody biomass, such as poplar, in commercial quantities.
Sceptics regard this as unlikely to become a carbon-neutral commercial process due to the energy inputs required to maintain the system. For decades, researchers have sought to house termites on a commercial scale (like worm farms) to break down woody debris and paper, but funding has been scarce and the problems of developing a continuous process that does not disrupt the termites' homeostasis have not been overcome.[10]
Ground Water divining in Ancient India
Varaha Mihira (505 C.E- 587 C.E), the famous astronomer, mathematician and astrologer of Ancient India, in his treatise "Brihat Samhita" also spelled "Vrahat Sanhita" refers to Dakargala (Sanskrit word meaning 'Science of Underground Water exploration'), wherein the role of termite knolls, as an indicator of underground water has been elaborately explained.[11]
In Verse.S.54.9 of the Samhita, it is stated that sweet ground water would be found near a termite mound located east of a Jambu tree (botanical names - Eugenia Jambus,Engenia Jambolana), at a specific distance and a specific depth of 15 ft to the south of the tree.[11]
The above verse has been justified with an explanation:
Without exception the water requirements of the insects are generally very high, and they need to protect themselves against fatal desiccation by living and working within the climatically sealed environment of their nest or within earth covered galleries. According to present level of research, the atmosphere within the nest has to be maintained practically saturation moisture level ( 99-100 % humidity). It is a matter of common observation that whenever a termite nest or runway, is damaged, the insects immediately rush to the breach and repairs it with wet soil brought up from within the nest. From an over-all consideration of the evidence it seems to be safe to conclude that, while normally the insects use every readily available source of water close to the ground surface, under condition of severe climatic stress, they can and they probably do descend to the water table, no matter how deep it may be. Hence, a well-developed, active, permanent colony of mound-building termites can be taken as an indication of underground springs in proximity[11].
Two examples mentioned in the referred publication are, a) termiteries seen in the Katanga province (Congo Kinshasa) right up to the hill slopes where springs emerge, b) in the dry jungle uplands of coastal zone of Karanataka state (old Mysore state) and c) in the Deccan Plateau area[11].
It is also asserted in the verse Vr.S.54.85 that among a group of termite mounds, a water vein is sure to be found below the taller of the mounds. Verse 52 mentions that in a desert region, if a group of five termite mounds are found, and if the middle one is in white colour, then water will be found within a depth of Fifty five Purushas (in Sanskrit one Purusha is equivalent to 7.5 ft) or 412.5 ft[11].
As a common observation of a combination of different symptoms, termite mounds are said to be found close to trees, and ancient Hindus exploited this knowledge in the exploration of underground springs.[11].
Ecology
Ecologically, termites are important in nutrient recycling, habitat creation, soil formation and quality and, particularly the winged reproductives, as food for countless predators. The role of termites in hollowing timbers and thus providing shelter and increased wood surface areas for other creatures is critical for the survival of a large number of timber-inhabiting species. Larger termite mounds play a role in providing a habitat for plants and animals, especially on plains in Africa that are seasonally inundated by a rainy season, providing a retreat above the water for smaller animals and birds, and a growing medium for woody shrubs with root systems that cannot withstand inundation for several weeks. In addition, scorpions, lizards, snakes, small mammals, and birds live in abandoned or weathered mounds, and aardvarks dig substantial caves and burrows in them, which then become homes for larger animals such as hyenas and mongooses.
As detrivores, termites clear away leaf and woody litter and so reduce the severity of the annual bush fires in African savannas, which are not as destructive as those in Australia and the USA.
Globally, termites are found roughly between 50 degrees North & South, with the greatest biomass in the tropics and the greatest diversity in tropical forests and Mediterranean shrublands. Termites are also considered to be a major source of atmospheric methane, one of the prime greenhouse gases. Termites have been common since at least the Cretaceous period. Termites also eat bone and other parts of carcasses, and their traces have been found on dinosaur bones from the middle Jurassic in China.[12]
Plant defences against termites
Many plants have developed effective defences against termites, and in most ecosystems, there is an observable balance between the growth of plants and the feeding of termites. Defence is typically achieved by secreting anti-feedant chemicals (such as oils, resins, and lignins) into the woody cell walls. This reduces the ability of termites to efficiently digest the cellulose. Many of the strongly termite-resistant tree species have heartwood timber that is extremely dense (such as Eucalyptus camaldulensis) due to accretion of these resins. Over the years there has been considerable research into these natural defensive chemicals with scientists seeking to add them to timbers from susceptible trees. A commercial product, "Blockaid", has been developed in Australia and uses a range of plant extracts to create a paint-on nontoxic termite barrier for buildings. In 2005, a group of Australian scientists "discovered" (announced) a treatment based on an extract of a species of Eremophila that repels termites.[13] Tests have shown that termites are strongly repelled by the toxic material to the extent that they will starve rather than consume cross treated samples. When kept in close proximity to the extract, they become disoriented and eventually die. Scientists hope to use this toxic compound commercially to prevent termite feeding.
Taxonomy, evolution and systematics
Recent DNA evidence[14][15] has supported the nearly 120-year-old hypothesis, originally based on morphology, that termites are most closely related to the wood-eating cockroaches (genus Cryptocercus), to which the singular and very primitive Mastotermes darwiniensis shows some telltale similarities. Most recently, this has led some authors to propose that termites be reclassified as a single family, Termitidae, within the order Blattaria, which contains cockroaches [16][17][18]. However, most researchers advocate the less drastic measure of retaining the termites as Isoptera but as a group subordinate to true roaches, preserving the internal classification of termites [19].
Evolutionary history
The oldest unambiguous termite fossils date to the early Cretaceous, although structures from the late Triassic have been interpreted as fossilized termite nests.[20] Given the diversity of Cretaceous termites, it is likely that they had their origin at least sometime in the Jurassic. Weesner believes that Mastotermitidae termites may go back to the Permian[21] and fossil wings have been discovered in the Permian of Kansas which have a close resemblance to wings of Mastotermes of the Mastotermitidae, which is the most primitive living termite. It is thought to be the descendant of Cryptocercus genus, the wood roach. This fossil is called Pycnoblattina. It folded its wings in a convex pattern between segments 1a and 2a. Mastotermes is the only living insect that does the same,[22]
It has long been accepted that termites are closely related to cockroaches and mantids, and they are classified in the same superorder (Dictyoptera), but new research has shed light on the details of termite evolution.[23] There is now strong evidence suggesting that termites are really highly modified, social, wood-eating cockroaches. A study conducted by scientists has found that endosymbiotic bacteria from termites and a genus of cockroaches, Cryptocercus, share the strongest phylogenetical similarities out of all other cockroaches. Both termites and Cryptocercus also share similar morphological and social features—most cockroaches do not show social characteristics, but Cryptocercus takes care of its young and exhibits other social behaviour. As mentioned above, the primitive Giant Northern Termite (Mastotermes darwiniensis) exhibits numerous cockroach-like characteristics that are not shared with other termites.
Systematics
As of 1996, about 2,800 termite species are recognized, classified in seven families[1]. These are arranged here in a phylogenetic sequence, from the most basal to the most advanced:
- Mastotermitidae (1 species, Mastotermes darwiniensis)
- Hodotermitidae (3 genera, 19 species)
- Hodotermitinae
- Kalotermitidae (22 genera, 419 species)
- Termopsidae (5 genera, 20 species)
- Termopsinae
- Porotermitinae
- Stolotermitinae
- Rhinotermitidae (14 genera, 343 species)
- Coptotermitinae Holmgren
- Heterotermitinae Froggatt
- Prorhinoterminae Quennedey & Deligne, 1975
- Psammotermitinae Holmgren
- Rhinotermitinae Froggatt
- Stylotermitinae Holmgren, K & N, 1917
- Termitogetoninae Holmgren
- Serritermitidae (1 species, Serritermes serrifer)
- Termitidae (236 genera, 1958 species)
- Apicotermitinae (42 genera, 208 species)
- Foraminitermitinae (2 genera, 9 species)
- Macrotermitinae (13 genera, 362 species)
- Nasutitermitinae (80 genera, 576 species)
- Sphaerotermitinae (1 genera, 1 species)
- Syntermitinae (13 genera, 99 species)
- Termitinae (90 genera, 760 species)
The most current classification of termites is summarized by Engel & Krishna (2004).
No comments:
Post a Comment