Termite Damage

 Appearance and morphology : Termites only superficially resemble ants; their "white ant" misnomer arises from their similar size and social habits. Compared with ants, they are softer, whiter, shorter-legged, fatter and generally much slower moving. Most importantly, they are not at all closely related to ants. Ants, along with bees and wasps, belong to the Order Hymenoptera. Termites are much closer to cockroaches and mantids, and all three are sometimes clumped into a super order called Dictyoptera. Some scientists have concluded that termites should be classified as a family Termitidae within the cockroaches’ order Blattodea.

Termites have biting mouthparts and their soft bodies are small, rarely over 1 cm in length. They typically inhabit dark nests and tunnels, only venturing out when the winged alates emerge to leave their parent colony, when constructing shelter or, in the case of grass- and leaf-litter-feeders, when harvesting their food. The bodies of flying individuals are darker, while termites which remain in the nest are generally whitish with only their heads being lightly pigmented. The deciduous wings of termites are long and slender, in two pairs that are similarly sized and shaped. The name of the termites’ order is derived from their having equal wings, iso means equal and pteron means wing. The wings are quickly shed after flight with a simple body flick when the swarming termites find a new nest site, pair up and dig in. The remnant of a wing is a distinct triangular scale.

 Social structure and behavior: As social insects, termites live in colonies that, at maturity, number from several hundred to several million individuals. They are a prime example of decentralised, self organised systems using swar intelligence and use this cooperation to exploit food sources and environments that could not be available to any single insect acting alone. A typical colony contains nymphs (semi-mature young), workers, soldiers and reproductive individuals of both sexes, sometimes containing several egg-laying queens. 

Reproductives : A female that has flown, mated and is producing eggs, is termed a "Queen". Similarly, a male that has flown, mated and remains in proximity to a queen, is termed a "King". These anthropomorphic terms have caused great misunderstanding of colony dynamics. Research using genetic techniques to determine relatedness of colony members is showing that the idea that colonies are headed by a monogamous royal pair is at least sometimes incorrect. Multiple pairs of reproductives within a colony are not uncommon, but for the families Rhinotermitidae and Termitidae, at least, 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 can lay several thousand eggs a day. In physogastric species, the queen adds an extra set of ovaries with each moult, resulting in a greatly distended abdomenand increased fecundity. The distended abdomen increases her size in some species to as much as 10    centimetres, hundreds of times the original size, effectively immobilizing her. In times where these huge queens must be moved to a new chamber it requires a group effort to move her and hundreds of workers are required to push her. The queen is widely believed to be a primary source of pheromones useful in colony integration. As a reward for attending workers a juice is secreted from the queen’s posterior for the workers to drink.

The king remains only slightly bigger than an average termite and continues to mate with the queen for life. This is very different from ant societies, which have colonies with only a queen which mates once with the male(s) and stores his gamates for life. Males in ant colonies die immediately after mating, unlike termite male alates, which become kings and live with the queen.

The 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). Immature alates still going through incomplete metamorphosis form a sub-caste in certain species of termites, functioning as functional workers (‘pseudergates’) and also as potential supplementary reproductives. Supplementaries have the ability to replace a dead primary reproductive and in at least some species several are recruited once a primary queen is lost. 

Workers: Worker termites undertake the labours of foraging, food storage, brood, nest maintenance and some of the defense effort in certain species. Workers are the main caste in the colony for the digestion of cellulose in food. This is achieved in one of two ways. In all termite families except the Termitidae, there are flagellates( Protista) in the gut that assist in cellulose digestion. However, in the Termitidae, which account for approximately 60% 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 can digest wood in the absence of their symbiotic microbes.

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 as it frees the parents from feeding the young, allowing for the group to grow much larger and ensuring that the gut symbionts are transferred from one generation to another.

Termite workers are generally blind due to undeveloped eyes. Despite this limitation they are able to create elaborate nests and tunnel systems using a combination of soil, chewed wood /cellulose, saliva and faeces. Some species have been known to create such durable walls that industrial machinery has been damaged in an attempt to break their tall mounds. Some African and Australian species have mounds more than 4 metres high. The nest is created and maintained by workers with many distinct features such as housing the brood, water collection through condensation, reproductive chambers, and tunnel networks that effectively provide air conditioning. A few species even practice agriculture, collecting plant matter to feed fungal gardens, upon which the colony then feeds.

Soldiers:  The soldier caste has anatomical and behavioural specializations, primarily useful against ant attack. The proportion of soldiers within a colony varies both within and between species. Many soldiers have jaws so enlarged that they cannot feed themselves, but instead, like juveniles, are fed by workers. The pan-tropical sub family Nasutitermitinae (which should probably have the South American species separated) have soldiers with the ability to exude noxious liquids through either a horn-like nozzle (nasus) or simple hole in the head (fontanelle). Fontanelles which exude defensive secretions are also 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, soldiers developing from the reproductive line have at least partly functional eyes.

It’s generally accepted that the specialization of the soldier caste is principally a defense against predation by ants. The wide range of jaw types and phragmotic heads provides methods which 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 blindly biting at intruders or shooting toxic glue from the nasus.This formation involves self sacrifice because once the workers have repaired the breach during fighting no return is provided, causing the death of all the defenders.

Termites undergo incomplete metamorphisis, with their freshly hatched young taking the form of tiny termites that grow without significant morphological changes. Some species of termite have been known to have small groups of extremely large soldiers (3 times normal size). Though their value is unknown speculation indicates 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. Some termite taxa do not have any soldiers; perhaps the best known of these is the Apicotermitinae.

Diet: 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 structures.

All termites eat cellulose in its various forms as plant fiber. Cellulose is a rich energy source (think of the amount of energy released when wood is burned), but remains difficult to digest. Termites rely primarily upon symbiotic protozoa such as Trichonymphia, and other microbes in their gut to digest the cellulose for them, absorbing the end products for their own use. Gut protozoa such as Trichonymphia, 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 cellulose enzymes. However, they still retain a rich gut fauna with bacteria dominant. Due 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.

 Mounds: In some regions, notably arid tropical savannas, termites construct extremely large and elaborate mounds which house their colonies. These mounds can have very distinctive forms, such as those of the compass termite (Amitermes meridionalis & Amitermes laurensis) which build tall wedge-shaped mounds with the long axis oriented approximately north-south. This orientation has been experimentally shown to help in thermoregulation. The column of hot air rising in the above ground mounds helps drive air circulation currents inside the subterranean network. Some mounds can reach heights of 6 metres, but most species build mounds of less than two metres height. The structure of these mounds can be quite complex. The temperature control is essential for those species that cultivate fungal gardens and even for those that don’t, much effort and energy is spent maintaining the brood within a narrow temperature range, often only plus or minus one degree C over a day. 

Coptotermes     Common Name:   Subterran Termite

Description: Coptotermes are widely distributed across Australian and are most easily recognised by the milky substance that the soldiers produce when disturbed. All Coptotermes secies form large colonies which likely contain millions of individuals. Colonies may be found in nests under the ground, in tree stumps, in hollow trees, in living trees or in conical mounds above the ground. All Coptotermes species are wood feeders, with some known to cause severe damage to living trees and other wood including that utilised by humans.  Coptotermes can be found in all states in Australia but only builds mound nests in the northern and south-west areas of its range. Although, Coptotermes can be found throughout mainland Australia, they cause more damage to property than any other species. It is aggressive in its search for food and will attack many items other than wood in its search for cellulose materials. It will damage wall lining boards, electrical wiring and even personal possessions. Colonies often nest in trees or stumps but can form nests without ground contact.

 

Heterotermes

Description: Heterotermes are a significant structural pest through Queensland, northern WA and the NT. It is only in southern Australia where they are a minor nuisance. They are generally considered to do little damage to timber in service, restricting their attention to weathered timber fences, decking and posts. Occasionally they can cause superficial damage to sound timber. 

 

Mastotermes       Common name:      Mus musculus

Description: Mastotermes darwiniensis, the Giant Northern Termite, is the most primitive of the commercially significant species. It shows an ability for sub-colonies to split from the main colony and produce queens, without a mating flight. Eventually a network of interconnecting sub-colonies is established, which makes control difficult. These large termites can devastate buildings, bridges, poles, trees and crops such as sugarcane. Mastotermes is found mainly north of the Tropic of Capricorn.

Microcerotermes

 Identification: Significant damage to timbers in buildings is rare.

Hosts: Mainly decayed timbers in contact with ground, such as poles or posts or fences.

Distribution: Coastal QLD and NSW

Nesting: Numerous nest types. Either under ground, small mounds, or arboreal (Including on posts or poles). 

Nasutitermes

 Description: There are several species of Nasutitermes which may damage timber in service. Soldier termites of these species are distinguished by their pointed heads. Nasutitermes exitiosus usually builds a low mound and is more common across Southern Australia. Nasutitermes walkeri builds part of its colony as a nest on the branch of a tree; the rest is constructed in the ground beneath it. This genus will mainly attack hardwood such as that found in fences and timber decking.The adult soldiers of Nasutitermies spp. have bulbous heads drawn out into a long snout at the front. The snout can be used to squirt fluid that is irritating to other animals. 

Schedorhinotermes

Description: These termites can cause damage approaching the severity caused by Coptotermes. They build fragile nests in places such as old tree trumps, in timber buried in the ground, in filled patios and under fireplaces. The damage they cause is distinctive. Although it can be severe it is often patchy, with huge gouges taken out of sound timber, particularly around nails in floor boards or other timbers. Schedorhinotermes colonies contain major and minor soldiers. 

 We acknowledge and thank Dr Ken Walker, Senior Curator, Entomology, Museum Victoria for the information and pictures. http://museumvictoria.com.au