Page Contents:
2. Biology:
2.1
Terminology and Scope
2.2
Anatomy
2.3
Foraging for Food and Water
2.4 Feeding and Digestion
2.5 Colony Organisation
2.6
Nesting Habits
2.7 Identification
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2.1 Terminology and Scope:
Subterranean termites, or termites for short, are also often referred to
as white ants in
Australia. The term white ant is
misleading since termites are not related to ants, don’t look like ants,
and are not white.
There are two main types of termites;
- Subterranean termites which must begin a nest
in the ground, hence the subterranean part of the name, and
- Drywood
termites that nest in timber without any contact with the ground.
Generally, drywood termites in Australia
are of academic interest only, except in very isolated situations.
From here on, when I refer to termites, I mean
subterranean termites specifically.
Termites are a native insect of Australia and can be found almost
everywhere on the mainland. They are typically destructive pests of
timber structures in the tropical and subtropical parts of the world. In Australia the
further north you go, termites are more prevalent and more destructive.
Having said that, it should be remembered that termites can be just as
much a problem for householders in Perth,
Adelaide
and Melbourne
as they are for residents of Sydney, Brisbane and Darwin.
There are several hundred termite species in Australia. Only
a few species have the potential to cause major damage to homes and
timber structures.
The three most economically significant species are
Coptotermes sp., Schedorhinotermes
sp. and Mastotermes sp..
Species that sometimes infest buildings and
structures but generally cause low levels of structural damage include
Nasutitermes sp.,
Heterotermes sp. and Microcerotermes sp.
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2.2 Anatomy:
Termites are insects. They have a three segmented
body (head, thorax and abdomen), although there is no visible separation
or constriction between the thorax and abdomen of termites. When you
look at a termite you will only be able to define two segments, head and
body (thorax/abdomen).
If you are looking at an insect that you think may
be a termite and you can see three clearly defined segments, it is not a
termite. It is probably an ant.
Termites have six legs (three pairs) attached to
their thorax. If you see more or less than six legs it is not a termite.
Apart from the Alate termite caste, termites do no
have wings.
If you look closely you will see termites have one
pair of antennae which are straight.
If you are looking at an insect that you think is a
termite and the antennae have a bend or elbow, you are not looking at a
termite. It is probably an ant.
If you look even closer at the head you will not
see eyes. Worker and soldier termites have no eyes and are technically
blind. However I have observed termites responding to the presence of
light (or the heat associated with light) on numerous occasions.
Termites may not be able to see objects but probably can distinguish a
gradient of light and dark.
Termites don’t have a hardened outer shell
(exoskeleton) like beetles, cockroaches and ants. The termite ‘skin’ is
soft and translucent. In the abdomen area of workers you can often see
through the skin and distinguish large internal structures like the gut.
This soft skin allows moisture to evaporate quickly from the termite
body. This is one of the termites ‘Achilles Heals’; because it means
that termites need to live and work in conditions of very high humidity
to slow the rate of evaporation. It also means termites need to have a
constant, reliable supply of water to support the colony. Termites are
far more dependant on water to drink, than on wood to eat.
The availability of water is more critical to
termite survival than the availability of food (wood). As we will
discuss later in this article, reduction of water, moisture and humidity
in and around buildings is critical to the successful management termite
infestation risk. Much, much more important than limiting available
sources of wood.
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2.3 Foraging for Food and Water:
The foraging
behaviour of termites (process of finding food) is a common source of
misunderstanding by consumers and the source folklore dispensed by
unethical termite treatment salesmen.
There is fairly solid
scientific evidence that termites do not see, do not smell and do not
sense the environment much beyond the boundary of their tunnel system.
Termite foraging
behaviour is random. Termites tunnel through the environment by eating
the material at the end of the tunnel. They could be likened to human
miners digging a tunnel though the earth in search for a seam of gold.
The seam of gold for termites is a source of cellulose (wood or plant
material) or water. This is
a fairly random process. It may appear that they know where there is a
source of food (i.e. your house) but they find your house by a random
process. If they knew about the presence of a house then every house
would be infested every year; because suburban houses represent the most
attractive source of food for termites in the surrounding environment.
While the process of
foraging is generally random, termites do follow natural and man made
structures. For example it is not uncommon for termites to follow pipes
and conduits that run through the surrounding environment into
buildings. These pipes and conduits can unwittingly, but effectively,
lead the termites to the side of the building or even into the building.
Combine the presence of a pipe entering a building with a water leak
from the pipe and you have an effective, irresistible invitation for
termites to enter the building.
Equally a piece of timber connecting the building to the ground
is also an open invitation for termites to enter the house.
Not only are termites
foraging for food (wood) but they are also seeking reliable sources of
water to ingest. This ‘drinking’ usually means eating wet soil or under
ideal circumstances wet wood.
Foraging for food and
therefore the tunnelling process of termites is relentless. The process
continues day and night, winter and summer. Foraging and feeding does
slow under dry and or cold conditions. In the suburban environment there
are often artificial supplies of water (leaking pipes, air-conditioner
condensation, for termites to exploit even during prolonged periods of
drought.
Soil temperature usually remains
within a range suitable for optimum termite activity in most of Australia,
during most of the year, although air temperature varies widely. It
would only be during the depths of winter in the southern latitudes and
the height of summer in the northern latitudes that soil temperature may
become limiting to termite activity.
In the process of
foraging for food termites will eat through materials with no
nutritional value. The soil is the major component of the material eaten
in search of food. However termites have been known to tunnel (randomly
eat) through seemly inedible materials such as lead sheathing on cables,
rubber tyres on tractors and hard plastics. In the building situation
termites can tunnel through plasterboard lining, carpet underlay,
plastic sheeting and the list goes on.
Termites can not
tunnel though solid concrete. They can however widen a crack in the
concrete if they are able to get through in the first place. This
widening may have more do with the effect of their slightly acidic
excretion (sweat) or physical erosion by termites rubbing over the
surface, than the process of eating.
In summary, there are
few natural materials that termites are unable to ‘eat’ through, even
material of no nutritional value.
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2.4 Feeding and Digestion:
Termites feed on cellulose (plant material). The
main component of wood is cellulose. It is cellulose that the termites
need for food. Therefore it is not just the structural and building
timbers on which termites feed but anything of plant material origin
(e.g. paper, cardboard, ply-board, furniture, cotton cloth and
timber musical instruments etc).
It not just the structure of the building that is in danger from termite
attack but also much of the contents of the building.
Termites eat plant material (commonly wood) as a
source of cellulose. Cellulose forms the structure of plant tissues. For
example cellulose comprises about 50% of wood and 90% of cotton fibres.
Cellulose is a polymer (long chain) of thousands of glucose (sugar)
molecules.
Termites can not digest cellulose. Termites must
rely on micro-organisms (bacteria and protozoa) in their intestines
(gut) to actually digest the cellulose and release the sugars. In this
respect, the digestion system of termites is similar to that of the cow.
There is a symbiotic relationship between the
termites and the micro-organisms that live in the termite’s intestines.
The micro-organisms must rely on the termites to find and gather
cellulose. The termites must rely on the micro-organisms to convert the
cellulose to something the termites can digest. Neither group can live
without the other.
An understanding of termite feeding habits and
preferences is critical to understanding the how, why, where and when of
termite infestations of homes and other timber structures.
Worker termites are responsible for all the
foraging for food, gathering of food, transport of food, distribution of
food, the removal of faeces (waste) from nest and the disposal of
faeces.
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2.5 Colony Organisation:
All termites are called social insects because they
work and live together in strictly ordered and organised colonies or
nests. Mature termite
colonies may number in the hundreds of thousands or even millions of
individuals. A mature Queen
may be capable of producing over 20,000 eggs per day. Each colony is
composed of individuals belonging to defined castes. Each caste has
specific jobs or responsibilities to perform within the colony.
Once an individual termite forms into a worker or soldier the
process can not be reversed.
The caste system is detailed below:
1. The Reproductives caste, these are the Queen and
King of the colony. The Queen termite, like the Queen Bee, is the only
egg laying individual. Following swarming each mated pair drops its wing
and seeks out a suitable place to start a new colony. The King’s
appearance alters little, but the Queen's abdomen becomes enormously
distended until she becomes little more than a large, immobile egg
laying machine. The Queen
termite controls the colony by producing hormone like chemicals called
pheromones. The King inseminates the Queen to provide the other half of
the genetic material required for sexual reproduction.
2. The Alate caste, or winged termites, often
referred to in
Australia
as flying ants, may be present in the colony at certain times each year.
Alates are fully formed adult insects with eyes, wings and reproductive
organs. The purpose of
alates is to form new colonies and sustain the species. Alates
must begin a colony in the ground.
Alates can not fly into your house
and start a nest.
Alates usually swarm (leave the colony) in late
spring to late summer, to mate and begin new colonies. Successful alates
become the Queen and King of a new colony. One of the characteristics of
the Alate caste is their ability to shed their wings after the swarming
flight. It is often the presence of these gossamer like wings caught in
spider’s webs, littering the floor or floating on the top of the pool,
that alert home owners to an occurrence of a termite swarm in the
previous night. Swarming usually occurs in the late afternoon or early
evening after a storm or heavy rain event, while the atmospheric
humidity is high.
3. The Supplementary Reproductive caste, are
produced by most species of termites and are potential alates, but do
not leave the colony during swarming flights. Supplementaries are
thought to be Queens
and Kings in waiting. For example if the current Queen was to die and
there was no replacement, the colony would soon die. A supplementary
Queen takes the place of the dead Queen and the colony survives. This
replacement of reproductive castes members by supplementary caste
members helps to explain how a termite colony can survive and grow for
many decades.
4. The
worker caste, numerically dominates the colony population. Workers are
wingless, sexually sterile and blind. The workers are aptly named
because as a group they do all the work to support the colony. Workers
build the nest and galleries, tend the eggs and young, gather food and
feed other castes incapable of feeding themselves (king, queen and
soldiers). It is the worker termite caste that eats timber and causes
the damage in buildings and other structures.
5. The soldier caste is distinguished by their head
which is modified, heavily 'armoured' and pigmented. It is the head
modification of soldiers that forms the basis for the scientific
identification of termite species. Because the jaws of the soldier caste
are modified or specialised, they cannot feed themselves and therefore
soldiers must be fed by the workers. The primary function of the
soldiers is to defend the colony against enemies such as ants.
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2.6 Nesting Habits:
A termite mound is the most familiar form of
termite nest in
Australia,
however not all species inhabit this type of nest structure. Some prefer
a completely underground existence; others build their nest within dead
or living trees and stumps. Some construct no recognisable nest at all.
Still other species prefer to attach their nest to a tree but maintain
soil connection via galleries or tunnels running down the trunk.
In reality, for the majority of regions in Australia the
termite species that cause the most damage to buildings do not build a
visible nest structure above ground level. So as general rule of thumb,
if you can see a termite nest, it is a species of minor economic
importance.
Nests are built from the droppings of the worker
termites. Workers gather all the faeces produced by the other castes by
eating the faeces. Workers then move to an area where the colony is
building a structure (e.g. nest enlargement, shelter tube, mud tunnel)
and deposit their droppings as the building blocks of structure. The
ability of termites to build highly complex structures is one of the
wonders of nature.
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2.7 Identification:
If you are an entomologist (one who studies
insects) the identification of termite species is very interesting. For
you the householder or building owner the only question you need to
answer in identifying termites is as follows;
Q1. Is the insect I have found a termite…..yes or
no?
To be a termite it must have only two visible
segments, six legs, a pair of straight antennae and no wings
If yes or if your not sure then….
Q2. Who am I going to call to get further advice
and recommendations?
Be aware that most of the time you will not
actually see termites when your house is infested, so identification of
the actual insect is not something you will need to do.
You will usually find damage or evidence of termite
activity. Do not go digging around
in the damage to find live termites. Even the professional should not do
this. Professionals can generally identify the offending termite species
accurately by observing the termite workings, mud packing and galleries.
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