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| Formosan subterranean termite soldiers (red colored heads) and workers (pale colored heads).|
Formosan subterranean termite soldiers (red colored heads) and workers (pale colored heads).
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera (see taxonomy below), but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea. While termites are commonly known, especially in Australia, as "white ants," they are only distantly related to the ants.
As eusocial insects, termites live in colonies that, at maturity, number from several hundred to several million individuals. Colonies use decentralised, self-organised systems of activity guided by swarm intelligence which exploit food sources and environments unavailable to any single insect acting alone. A typical colony contains nymphs (semi-mature young), workers, soldiers, and reproductive individuals of both genders, sometimes containing several egg-laying queens.
A female that has flown, mated, and is producing eggs is called a "queen." Similarly, a male that has flown, mated, and is in proximity to a queen is termed a "king." Research using genetic techniques to determine relatedness of colony members has shown that the original idea that colonies are only ever headed by a monogamous royal pair is wrong. Multiple pairs of reproductives within a colony are commonly encountered. In the families Rhinotermitidae and Termitidae, and possibly others, sperm competition does not seem to occur (male genitalia are very simple and the sperm are anucleate), suggesting that only one male (king) generally mates within the colony.
At maturity, a primary queen has a great capacity to lay eggs. In physogastric species, the queen adds an extra set of ovaries with each molt, resulting in a greatly distended abdomen and increased fecundity, often reported to reach a production of more than 2,000 eggs a day. The distended abdomen increases the queen's body length to several times more than before mating and reduces her ability to move freely, though attendant workers provide assistance. The queen is widely believed to be a primary source of pheromones useful in colony integration, and these are thought to be spread through shared feeding (trophallaxis).
The king grows only slightly larger after initial mating and continues to mate with the queen for life (a termite queen can live for forty-five years). This is very different from ant colonies, in which a queen mates once with the male(s) and stores the gametes for life, as the male ants die shortly after mating.
The winged (or "alate'") caste, also referred to as the reproductive caste, are generally the only termites with well-developed eyes, although workers of some harvesting species do have well-developed compound eyes, and, in other species, soldiers with eyes occasionally appear. Termites on the path to becoming alates (going through incomplete metamorphosis) form a subcaste in certain species of termites, functioning as workers ("pseudergates") and also as potential supplementary reproductives. Supplementaries have the ability to replace a dead primary reproductive and, at least in some species, several are recruited once a primary queen is lost.
In areas with a distinct dry season, the alates leave the nest in large swarms after the first good soaking rain of the rainy season. In other regions, flights may occur throughout the year, or more commonly, in the spring and autumn. Termites are relatively poor fliers and are readily blown downwind in wind speeds of less than 2 km/h, shedding their wings soon after landing at an acceptable site, where they mate and attempt to form a nest in damp timber or earth.
Worker termites undertake the labors of foraging, food storage, brood and nest maintenance, and some defense duties in certain species. Workers are the main caste in the colony for the digestion of cellulose in food and are the most likely to be found in infested wood. This is achieved in one of two ways. In all termite families except the Termitidae, there are flagellate protists in the gut that assist in cellulose digestion. However, in the Termitidae, which account for approximately 60 percent of all termite species, the flagellates have been lost and this digestive role is taken up, in part, by a consortium of prokaryotic organisms. This simple story, which has been in entomology textbooks for decades, is complicated by the finding that all studied termites can produce their own cellulase enzymes, and therefore might digest wood in the absence of their symbiotic microbes although there is now evidence suggesting that these gut microbes make use of termite-produced cellulase enzymes. Our knowledge of the relationships between the microbial and termite parts of their digestion is still rudimentary. What is true in all termite species, however, is that the workers feed the other members of the colony with substances derived from the digestion of plant material, either from the mouth or anus. This process of feeding of one colony member by another is known as trophallaxis and is one of the keys to the success of the group. It frees the parents from feeding all but the first generation of offspring, allowing for the group to grow much larger and ensuring that the necessary gut symbionts are transferred from one generation to another. Some termite species do not have a true worker caste, instead relying on nymphs that perform the same work without differentiating as a separate caste.
The soldier caste has anatomical and behavioural specializations, providing strength and armour which are primarily useful against ant attack. The proportion of soldiers within a colony varies both within and among species. Many soldiers have jaws so enlarged that they cannot feed themselves, but instead, like juveniles, are fed by workers. The pantropical subfamily Nasutitermitinae have soldiers with the ability to exude noxious liquids through either a horn-like nozzle (nasus). Simple holes in the forehead called "fontanelles" and which exude defensive secretions are a feature of the family Rhinotermitidae. Many species are readily identified using the characteristics of the soldiers' heads, mandibles, or nasus. Among the drywood termites, a soldier's globular ("phragmotic") head can be used to block their narrow tunnels. Termite soldiers are usually blind, but in some families, particularly among the dampwood termites, soldiers developing from the reproductive line may have at least partly functional eyes.
The specialization of the soldier caste is principally a defence against predation by ants. The wide range of jaw types and phragmotic heads provides methods that effectively block narrow termite tunnels against ant entry. A tunnel-blocking soldier can rebuff attacks from many ants. Usually more soldiers stand by behind the initial soldier so once the first one falls another soldier will take the place. In cases where the intrusion is coming from a breach that is larger than the soldier's head, defense requires special formations where soldiers form a phalanx-like formation around the breach and bite at intruders or exude toxins from the nasus or fontanelle. This formation involves self-sacrifice because once the workers have repaired the breach during fighting, no return is provided, thus leading to the death of all defenders. Another form of self-sacrifice is performed by Southeast Asian tar-baby termites (Globitermes sulphureus). The soldiers of this species commit suicide by autothysis—rupturing a large gland just beneath the surface of their cuticle. The thick yellow fluid in the gland becomes very sticky on contact with the air, entangling ants or other insects who are trying to invade the nest.
Termites undergo incomplete metamorphosis. Freshly hatched young appear as tiny termites that grow without significant morphological changes (other than wings and soldier specializations). Some species of termite have dimorphic soldiers (up to three times the size of smaller soldiers). Though their value is unknown, speculation is that they may function as an elite class that defends only the inner tunnels of the mound. Evidence for this is that, even when provoked, these large soldiers do not defend themselves but retreat deeper into the mound. On the other hand, dimorphic soldiers are common in some Australian species of Schedorhinotermes that neither build mounds nor appear to maintain complex nest structures. Some termite taxa are without soldiers; perhaps the best known of these are in the Apicotermitinae.
Termites are generally grouped according to their feeding behaviour. Thus, the commonly used general groupings are subterranean, soil-feeding, drywood, dampwood, and grass-eating. Of these, subterraneans and drywoods are primarily responsible for damage to human-made structures.
All termites eat cellulose in its various forms as plant fibre. Cellulose is a rich energy source (as demonstrated by the amount of energy released when wood is burned), but remains difficult to digest. Termites rely primarily upon symbiotic protozoa (metamonads) such as Trichonympha, and other microbes in their gut to digest the cellulose for them and absorb the end products for their own use. Gut protozoa, such as Trichonympha, in turn rely on symbiotic bacteria embedded on their surfaces to produce some of the necessary digestive enzymes. This relationship is one of the finest examples of mutualism among animals. Most so-called higher termites, especially in the Family Termitidae, can produce their own cellulase enzymes. However, they still retain a rich gut fauna and primarily rely upon the bacteria. Owing to closely related bacterial species, it is strongly presumed that the termites' gut flora are descended from the gut flora of the ancestral wood-eating cockroaches, like those of the genus Cryptocercus.
Some species of termite practice fungiculture. They maintain a “garden” of specialized fungi of genus Termitomyces, which are nourished by the excrement of the insects. When the fungi are eaten, their spores pass undamaged through the intestines of the termites to complete the cycle by germinating in the fresh faecal pellets. They are also well known for eating smaller insects in a last resort environment.
In captivity Edit
Few zoos hold termites, due to the difficulty in keeping them captive and the reluctance of authorities to permit potential pests. One of them is Zoo Basel in Switzerland. At Zoo Basel, two African termite (Macrotermes bellicosus) populations exist and thrive - resulting in very rare (in captivity) mass migrations of young flying termites. This happened last in September 2008, when thousands of male termites left their mound each night, died, and covered the floors and water pits of the house their exhibit is in.
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 U.S.A. Their role in bioturbation on the Khorat Plateau is under investigation.
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.
Termites divide labour among castes, produce overlapping generations and take care of young collectively.
- Main article: Termites - Nestbuilding
- Main article: Termites - Animal human interaction
Other behavior of note Edit
Taxonomy, evolution and systematicsEdit
Recent DNA evidence has supported the 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 Blattodea, which contains cockroaches. However, most researchers advocate the less drastic measure of retaining the termites as Termitoidae, an epifamily of the cockroach Order, which preserves the classification of termites at family level and below.
Evolutionary history Edit
The oldest unambiguous termite fossils date to the early Cretaceous, although structures from the late Triassic have been interpreted as fossilized termite nests. 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 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,
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. 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, such as laying its eggs in rafts and having anal lobes on the wings that are not shared with other termites.
- Kalotermitidae (22 genera, 419 species)
- Rhinotermitidae (14 genera, 343 species)
- Termitidae (236 genera, 1958 species)
The most current classification of termites is summarized by Engel & Krishna (2004).
- ↑ (22 June 2007)Hidden cellulases in termites: revision of an old hypothesis. Biology Letters 3 (3): 336–339.
- ↑ Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
- ↑ C. Bordereau, A. Robert, V. Van Tuyen & A. Peppuy (1997). Suicidal defensive behavior by frontal gland dehiscence in Globitermes sulphureus Haviland soldiers (Isoptera). Insectes Sociaux 44 (3): 289–297.
- ↑ The evolution of fungus-growing termites and their mutualistic fungal symbionts by Duur K. Aanen, Paul Eggleton, Corinne Rouland-Lefèvre, Tobias Guldberg-Frøslev, Søren Rosendahl & Jacobus J. Boomsma
- ↑ Fungus-farming insects: Multiple origins and diverse evolutionary histories by Ulrich G. Mueller & Nicole Gerardo
- ↑ [http://www.nzz.ch/nachrichten/panorama/im_zoo_basel_fliegen_die_termiten_aus__1.848530.html (German) Im Zoo Basel fliegen die Termiten aus]. Neue Zürcher Zeitung, retrieved 2011-05-21
- ↑ Lofjle & Kubiniok, Landform development and bioturbation on the Khorat plateau, Northeast Thailand, Nat.Hist.Bull.Siam Soc. (56), 1996 
- ↑ 403 Forbidden
- ↑ Lo, N. et al. Evidence for cocladogenesis between diverse dictyopteran lineages and their intracellular endosymbionts. Molecular Biology and Evolution, 20, 907–913 (2003)
- ↑ Ware,J.L. et al. Relationships among the major lineages of Dictyoptera: the effect of outgroup selection on dictyopteran tree topology. Systematic Entomology, 33, 429–450 (2008)
- ↑ Inward, D., G. Beccaloni, and P. Eggleton. 2007. Death of an order: a comprehensive molecular phylogenetic study confirms that termites are eusocial cockroaches. Biology Letters 3:331-335.
- ↑ includeonly>"Termites are 'social cockroaches'", BBC News, 13 April 2007.
- ↑ Eggleton, P. &al. (2007), Biological Letters, June 7, cited in Science News vol. 171, p. 318
- ↑ Lo, N. &al. (2007), Biology Letters, 14 August 2007, doi 10.1098/rsbl.2007.0264
- ↑ Gay and Calaby 1970 Termites of the Australian region. in; Krishna K Weesner FM eds. Biology of Termites, Vol. II Academic Press NY p401
- ↑ Weesner FM (1960) Evolution biology of termites. Annual Review of Entomology. 5; 153-170.
- ↑ Tilyard RJ (1937) Kansas Permian insects.. Part XX the cockroaches, or order BlattariaI, II Am. Journal of Science 34; 169-202, 249-276.
- ↑ Evidence for Cocladogenesis Between Diverse Dictyopteran Lineages and Their Intracellular Endosymbionts
- ↑ Engel, M.S. and K. Krishna (2004). Family-group names for termites (Isoptera). American Museum Novitates 3432 (1): 1–9.
- Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects, Cambridge University Press.
- Termite terms
- Cretaceous termites
David Attenborough, Life in the Undergrowth, Episode 5 Supersocieties, 37 mins and 15 secs ff.
Abe T., Bignell D.E., Higashi M. (eds.) (2000). Termites: evolution, sociality, symbioses, ecology, ecolab, Kluwer academic publishers.
- University of Nebraska page on Termites
- Termite Hub from National Pest Management Association - includes FAQs, types of termites, etc.
- A summary of termite control methods
- University of California advice on Drywood Termites
- Termite Pest Control Information - USA National Pesticide Information Center
- Catalogue of the termites of the World
- Pictures of termites
- Transitional Species in Insect Evolution
- Cretaceous Termites and Soil Phosphorus
- Beneficial Uses of Termites
- Texas A&M University Department of Entomology - Center for Urban & Structural Entomology
- The Soul of the White Ant - Eugène N. Marais
- Termite Terminology - a glossary of terms
- Urban Entomology Program University of Toronto
- List of Termite Types
- Isoptera: termites (CSIRO Australia Entomology).
- 'Termite guts can save the planet', says Nobel laureate
- Amitermes floridensis , Florida darkwinged subterranean termite
- Coptotermes formosanus , Formosan subterranean termite
- Coptotermes gestroi, Asian subterranean termite
- Cryptotermes brevis, West Indian drywood termite
- Heterotermes sp., West Indian subterranean termite
- Cryptotermes cavifrons, a drywood termite
- Incisitermes minor, western drywood termite
- Neotermes spp., Florida dampwood termites
- Prorhinotermes simplex, Cuban subterranean termite
- Reticulitermes spp., native U.S.A. subterranean termites
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