Spiders

What are the differences between spiders and insects?

Spiders have:

• two main body parts,
• eight walking legs,
• simple eyes
• piercing jaws (fangs),
• abdominal silk spinning organs,
• anterior abdominal genital opening.

Insects have three main body parts, six walking legs, compound eyes, antennae, chewing jaws (mandibles – often secondarily modified) and posterior abdominal genital opening.

Relatively speaking – the ArachnidaSpiders and their relatives are called arachnids. Arachnids have the head and thorax combined (cephalothorax) with simple eyes, jaws adapted for tearing or piercing prey, a pair of pedipalps and eight walking legs.

Arachnids include spiders, scorpions, pseudoscorpions, amblypygids( tailless-whipscorpions), schizomids (micro-whipscorpiones), palpigrades, harvestmen, ticks and mites.

Spiders are the only arachnids that have special glands in their abdomen which produce silk.

Midgets to monsters

A few spiders are so small and live such hidden lives that most of us never see them. Others are enormous.

Some of the smallest spiders in the world are anapid spiders, sometimes called armoured spiders because of the cuticular plates on their pinhead-sized bodies. Small spiders like anapids are usually found in damp, cool habitats like forest leaf litter and moss because their small bodies can lose water rapidly in dryer conditions. The largest spiders in the world include the South American Goliath Tarantula, some so big their legs can span a dinner plate. Such spiders may take decades to reach such a size. However, spider size is limited, partly because their respiratory physiology becomes less efficient at very large sizes.

Bodies bizarre

Many spiders have unusual body shapes and colours. Bizarre bodies can be helpful to spiders in various ways – to deceive and ambush prey, to capture particular sorts of prey, to avoid being eaten and to attract mates.

Cockroach

The mere mention of cockroaches brings about a strong reaction in many people. However, the fast moving, shiny, black or brown cockroaches commonly encountered by people in their homes are almost never native Australian cockroaches, but introduced pests.

The native Australian fauna is diverse, and rarely encountered by those who don’t venture far from urban areas. In fact, most of the Australian cockroach fauna will avoid human contact, preferring instead to forage among the vegetation, leaf litter and soil of undisturbed habitats.

Cockroaches are an ancient group, having remained relatively unchanged for hundreds of millions of years. They have a flattened body, long antennae and bristly legs. They have specialised sensors called ‘cerci’ (which are like rear-mounted antennae) that make them acutely aware of their surroundings. Any sign of danger sends them scuttling away. They also have the ability to eat almost anything. This is a great advantage when competing with other species for food.

Over the course of a year some female cockroaches can produce over 20,000 young. Their sheer numbers and indiscriminate feeding habits mean they may spread disease-causing organisms, although there is very little evidence to suggest this actually happens. They do, however, cause strong allergic reactions in some people.

Cockroach diversity

• Worldwide there are around 4,000 species of cockroaches.
• Approximately 450 of these are found in Australia.
• In Australia, only five species are considered pests.

The five pest species have become scavenging experts and have a long association with humans. In fact, some scientists believe that as early humans left Africa to colonise the world, cockroaches were probably not far behind.

Identification

Cockroaches have downward facing triangular-shaped heads. Their eyes are situated at the upper corners of the triangle and the mouth at the bottom corner. The head is partly or often completely concealed beneath thorax (mid-body). The body is usually flattened and elliptical in shape, with all the legs similar in shape and specialized for running or for digging.

Many Australian species are wingless in one or both sexes and some species have reduced wings. Winged forms fly readily when disturbed. Australian cockroaches range in length from 3 mm – 70 mm long.

Some species are brightly coloured, with orange, red, yellow and even blue present. Many of the brightest species are also day-active, being found on leaves and bushes in sunlight. One Australian species (Polyzosteria mitchelli) has transparent windows in the upper skin, although it is not known why.

Pest species are often flattened dorso-ventrally (from back to front) and are usually dark brown.

Habitat and BiologyMost cockroaches lay their eggs within a protective case called an ootheca. The ootheca may be carried for some time by the female before being deposited on the ground or buried in the soil.

Cockroaches of the family Blaberidae and Blattellidae, however display a few different reproductive strategies. Some push out the ootheca, but rather than depositing it somewhere, they retract it back into a uterus or brood sac where the eggs develop. Other species of Blaberidae do not form an ootheca but let the eggs pass directly from the ovipositor to the uterus where they develop. One species, Pycnoscelus surinamensis, reproduces parthenogenetically (without males) though males are occasionally born.

Cockroach oothecae are subject to parasitism by various groups of wasps. Some of which produce a single wasp adult per ootheca and some produce many more. Adult cockroaches are subject to predation by other invertebrates, birds, lizards, frogs and mammals as well as parasitism by round worms and wasps. Some species produce defensive secretions to ward off attackers, while other species can roll themselves into a ball to protect themselves.

The introduced species can often be found in sewers and around garbage, from where they can convey contaminated material into dwellings. Additionally, many introduced species carry bacteria such as Salmonella in their gut, which they can pass on through their saliva and faeces.

One Australian cockroach has been listed as an endangered species. The Lord Howe Island Woodeating Cockroach (Panesthia sp) is a wingless burrowing species which may have been wiped out following the introduction of rats to the island.

References

• Roth, L.M. 1991. Blattodea. In: Naumann et al. (eds.) Insects of Australia. Melbourne University Press, Australia.
• Rentz, D. 1996. Order Blattodea: Cockroaches. Chapter 14 in Grasshopper Country. UNSW Press, Sydney.

Termites

Termites are social insects that build large nests in soil or wood and can occasionally cause damage to wooden structures. They are sometimes called ‘white ants’, however they belong to a completely different insect group (Order Isoptera) to true ants (Order Hymenoptera).

Identification

Termites have pale brown to white bodies with a darker head and have no waist between the thorax and abdomen. The antennae have bead-like segments. The non-reproductive forms never develop wings, are blind and have thin skin that makes them vulnerable to drying out. Reproductive forms have two pairs of equal-sized wings, one pair of compound eyes and a thicker skin that protects them better from drying out when exposed.HabitatNests
Nests are formed either in trees, in soil mounds or underground. There are 5 main types of nests and many species will build more than one type of nest:

• Ground mounds
• Tree nests (outside tree, connected to internal cavity)
• Pole nests (on human structures such as fence posts and telegraph poles)
• Subterranean nests (underground, in soil, stumps and tree bases)
• Tree wood (inside the tree)

Nest humidity and temperature maintenance

Termite colonies are maintained at a high humidity. This protects the thin-skinned workers from drying out. Only when the external humidity is close to 100% can workers leave the nest to forage. This is especially the case for subterranean termite species, which gain most of their water from the soil. These species can only become pests in buildings where a constant water source is available. Indoor plants on pavers are a major cause, as are leaking pipes or roofs). Termites that nest in dry wood don’t have such strong water requirements and may attack wooden structures that are not necessarily very damp.

Nests are usually maintained at a temperature between 25°C – 36°C. This varies, depending on the species, the external temperature and the health of the colony. Healthy colonies are able to maintain this range during very hot and very cold external conditions.

Sometimes the nest shape is specifically designed to regulate temperature. The Compass Termite (Amitermes meridionalis) of the Northern Territory is known for its tall (3 m – 4 m) mound nests. These nests are thicker across their east-west axis (about 3 m) than along the north-south axis (about 1 m). This alignment means that the nest has the most protection from the hot summer sun as it moves east to west directly above the nest, but can still be warmed in winter when the sun is at a lower angle.

Feeding and Diet

Not all termites eat wood. Many species feed on grass and other matter and are not pests in buildings. Those species that do eat wood, get cellulose, sugars and starches (all carbohydrates) from the sapwood (outer wood) of trees and can also eat any wooden structures including logs, stumps and human constructions. They usually cannot eat the heartwood (innermost wood) as it tends to be much harder and can have toxins that repel the termites. Protein is obtained by eating fungi growing either in the humid nest – which also helps to keep the nest clean or from moist wood surfaces.

Many termite species have special gut organisms that help them to break down the woody cellulose into sugars that can be digested. Some species have protozoa (single-celled organisms) that produce enzymes to digest the cellulose while others have bacteria. These organisms are transferred from termite to termite during grooming sessions, especially from adults to young.

Grass and spinifex-eating species are very important in the savannah ecology of Northern Australia. The large amount of biomass that they process makes them the equivalent of large mammals that eat grasses in similar savannah or prairie habitats in other parts of the world.

Other behaviours and adaptations Castes Termites have several castes that have definite tasks within the colony:

• Queen/s: there is usually one main (first-form) queen who may have been the original founder of the colony. She may be larger than other colony members and swollen with eggs. Queens can live and reproduce for a long time (up to 20 years in some species). There may also be several supplementary queens in a colony, which can take over egg production from the primary queen when she dies.
• King: the original king fertilises the queen and helps to tend the young during the foundation of the colony.
• Workers: with white-bodies and thin skin, these are the most numerous in the colony and are involved in food gathering, feeding and tending the young and the queen and building or maintaining the nest. They rarely emerge from the nest or associated tunnels, as they dry up easily outside the humid nest environment.
• Soldiers: are the colony defenders. They are sometimes larger than workers, but mostly the same size, with darker heads. Two body forms are possible, with a particular species having one or the other: mandibulate (fully-jawed) and nasute (long-nosed). Some species also have two size classes – major and minor soldiers.
• Reproductives – both winged and wingless: these are the future kings and queens. Beginning as wingless nymphs, they develop by shedding their skin through several stages until they are fully winged adults. With darker, more durable bodies and compound eyes, they are able to survive for short periods outside the colony. They are destined to either leave the nest on a colonising flight or to take over from the queen if she dies.
• In some primitive termite species, there is no real worker caste, with the developing young taking on different roles as they moult. They may remain as undifferentiated workers, or moult into either a soldier or a reproductive form.

Life cycle

Termites undergo an incomplete metamorphosis, with three developmental stages:

• Egg
• Nymph
• Adult

The eggs hatch into nymphs (the first instar) that are fed by the workers, and these nymphs then moult several times, differentiating into worker, soldier or reproductive forms. Development into adult forms takes several months, depending on food, temperature and the size of the colony. Hormones are thought to control the numbers of each caste, with imbalances corrected by nymphs developing into whichever form is needed at the time.

Mating and reproduction

Colonising flightsTermite colonies are formed when the winged reproductive forms leave their original nest and take a colonising flight. These flights occur during warm humid weather and usually take place during spring and autumn. The right combination of climatic conditions increases the chances of success in founding a new colony.

Starting a colony

Once a suitable site is found, the mating pair (the new king and queen) drop their wings, hollow out a small mating chamber and the queen begins to lay a small number of eggs. Both the king and queen care for the young at this early stage. As the colony grows, the different castes take on their roles of workers and soldiers, leaving the queen to produce more and more eggs. She will produce 10-20 eggs in the early stages of a colony and may go on to lay over 1000 eggs a day after several years.

Economic/social impacts

Out of the 258 described (90 undescribed) termite species in Australia, only a few wood-damaging species are of concern to humans.

ClassificationOrder:

IsopteraSubclass:PterygotaClass:InsectaPhylum:ArthropodaKingdom:Animalia

References

• Gerozisis R. and P. Hadlington. 2001. Urban Pest Management. University of New South Wales Press, 4th Edition.
• P. Hadlington. 1987. Australian termites and other common timber pests. UNSW Press.

Ants

Ants are one of the most successful and ecologically important groups of terrestrial insects. They have colonised all terrestrial habitats throughout the world except the polar regions and highest mountaintops.

Ants can be found anywhere from coastal mangroves to urban backyards and inside our homes. Their success is because of their ability to communicate with each other. They have the most complex form of chemical communication in the animal kingdom and together they accomplish tasks beyond any individual insect.

Ants are formidable opponents and defend their foraging area from other animals. They can overwhelm by sheer weight of numbers and have defensive  armoury that may include fierce jaws and potent stings.

Features of ants:

• Ants are social insects. They exist in colonies that work together to gather food, rear young and defend their nest.
• Nests contain eggs, larvae, pupae and different types (or castes) of ants.
• Colony sizes range from a few individuals to tens of thousands. Each colony is made up of a queen, different-sized workers and a number of other castes at different stages of the colony cycle.
• The most commonly seen caste are workers.
• Winged ants leave the nest to mate and found new colonies in late summer and spring, often after rain. Many are eaten by birds and other predators.
• Ants are probably the most common insects encountered by humans.
• There are around 15,000 different species of ants worldwide.
• There are 1,275 Australian ant species described, but this could double with further research.
• Most species of Australian ants are found only in Australia.
• Many plants and other insects have evolved relationships with ants, even to the point where ants are a necessary part of their life cycle.
• Some birds place ants on their bodies to remove parasites. This is known as anting.

Other Pests

Silverfish

Silverfish belong to the Order Zygentoma (formerly Thysanura).

Size:

• 2 mm – 18 mm in length

Body:

• Column-like, tear-drop or spindle-shaped.
• Often hairy, with tufts common between eyes.
• Appears hard and covered in scales.
• Have tiny styli (soft finger-like projections) coming from the underside, some of the abdomen segments.

Antennae:

• Thread-like, with many segments.
• Longer than half the body length.

Eyes:

• Absent or small, berry-like and well separated.

Mouthparts:

• For chewing.
• Held in front or downwards at rest.

Wings:

• Absent.

Limbs:

• Six legs, short and stocky.

Abdomen tip:

• Three tails (two cerci and one middle filament), thread-like, and similar in size; at rest the two outer tails are directed at an angle away from the body.

Where are silverfish found?

• Under bark, rocks or among leaf litter.
• In soil or within caves.
• In the desert, as some are capable of absorbing water from the atmosphere.
• Living in ant and termite nests.
• In houses, where they favour areas of high humidity like bathrooms.

What do silverfish do?

• They often group together around food sources.
• When disturbed they remain still, run for cover or hop.
• They feed on fungi and plant material. In the home they may feed on starchy substances such as wallpaper glue, book bindings and photographs.
• They are normally active at night, if active during the day generally found in dark places.

What looks similar?

• Bristletails are easily confused with Silverfish. The difference between the two is that bristletails have large eyes that touch; their long middle tail, which is considerably longer than the cerci and they jump when disturbed.

Is it a Rat?

People may think that they have seen a baby Ring-tailed Possum or a native rat species. Unfortunately, in many cases it turns out to be a Black Rat, which is an introduced species and an age-old pest in and near human habitation. How can I tell whether I’ve seen a Black Rat or some other small mammal?

Behaviour

>The first thing to look at is the animal’s behaviour:

• Is it active during both day and night and is it relatively fearless around humans?
• Is it an agile climber, often seen in fruit trees, scaling fences, electrical wires or the roof of a house?
• Have you found a nest in your roof, made of shredded materials such as paper, insulation and other debris?
• Have you seen evidence of it feeding on grains and discarded foods, as well as fruit and even pet food?

All of these traits combined are characteristic of the Black Rat, which is often called the Roof Rat for its nesting and climbing habits. Native rats, such as the Bush Rat, are much more reserved animals, and are not found in places where human traffic is frequent – they prefer to nest in dense forest understorey, sheltering in short burrows under logs or rocks and they line their nests with grass. In fact, native rats such as the Bush Rat, have not been recorded in the inner city for many years. Possums nest in roofs, but are mainly active at night, and although they are agile climbers, they are heavier than rats in their movements. They may eat fruit and other human leftovers but tend to feed on native vegetation and are not found as often as rats are scavenging indoors and/or ransacking stored foodstuffs.

Tail

The next thing to look at is its tail. Is it?

• Long in relation to the body, sparsely haired, scaly and not used to grip branches when climbing?
  It is a Black Rat.
• Shorter than the body length?
  It is a Bush Rat.
• Long, with a white tip, furred on the upper surface, naked underneath and used to grip or hold branches with the end slightly curled?
  It is a Ring-tailed Possum.

Size, shape and colour

Lastly, the overall size, shape and colour of the animal should be looked at:

• Black Rats are about 16 cm to 20 cm long, and are charcoal grey to black or light brown above, cream or white below, with a sleek smooth coat. They have big thin ears and quite a round face.
• A Ring-tailed Possum of similar size would still be in its mother’s pouch or on her back, and would not be fully furred. An adult possum is much larger than a rat, reaching about 30 cm to 35 cm in length. The coat colour is quite variable, the ears are short with a white patch behind and the prehensile (gripping) tail has a white tip.
• The Bush Rat is charcoal grey to black or light brown above, cream or white below; has a sleek smooth coat, is grey to grey-brown or reddish above, grey or cream below and has dense soft fur. The ears are rounded.

What about other small native mammals? One animal that is sometimes seen and mistaken for a rat is in fact a small carnivorous marsupial – the antechinus. While there are several species of antechinus in Australia, they share several traits in common which, taken together can set them apart from rodents such as rats and mice. These include:

• Their front teeth:
  • Rodents have one pair of distinctive chisel shaped incisors that have hard yellow enamel on the front surfaces.
  • Antechinuses have four rows of small sharp incisors.
• Their ears. Many antechinus species have large thin crinkly ears that have a notch in the margin, although not all will have this notch.
• Their tail. Antechinuses have a sparsely haired tail, which is the same length as the body or shorter (65-110mm).
• Their habits. Antechinuses are mainly nocturnal insect eaters, which are found in forest habitats and are not found often in urban areas. They shelter in spherical nests in hollow logs or crevices, but can sometimes be found nesting in furniture, bush areas or farms.

Bees

There are over 1,500 species of native bees in Australia.

Bees belong to the insect Order Hymenoptera, which includes wasps, ants and sawflies. In Australia there are four main bee families: Apidae, Colletidae, Halictidae and Megachilidae.

Some Australian bees are solitary nesters, while others may share a nest and some are fully social species.

Although some bees sting, they are not considered to be pests. They play an important role in the Australian environment as key pollinators to many native plant species. Indigenous people have used both honey and the nests of native bees as valuable sources of food and wax, for many years.

Features of bees:

• They are vegetarian throughout their life cycle, eating nectar and pollen.
• They are generally furrier than wasps and have feathery or branched hairs.
• Some native bees use a special pollination technique called ‘buzz pollination’, which certain native flowering plants require for pollination.
• Stingless bees (Trigona and Austroplebeia species) are the only native bees that do not possess a sting.
• The females of all the other native bees have a sting but many are too small to deliver an effective venom dose to humans.
• Although not aggressive, the largest native species can deliver a painful sting.

References

CSIRO Entomology. 1991. The Insects of Australia. Melbourne University Press.
Dollin, A., M. Batley, M. Robinson & B. Faulkner. 2000. Native Bees of the Sydney Region: A Field Guide. Australian Native Bee Research Centre.
Hadlington, P. & Johnston, J. 1998. An Introduction to Australian Insects. UNSW Press: Sydney
Zbrowski, P. & Storey, R. 1995. A Field Guide to Insects in Australia. Reed Books: Sydney

Fleas

Fleas belong to the Order Siphonaptera.

What do fleas look like?

What do fleas look like?Size:

• 0.5 mm – 10 mm in length but most are shorter than 5 mm.

Body:

• Very thin as if pressed from the sides.
• Covered with hairs and spines directed backwards, some in comb-like formations.
• Appears hard.

Antennae:

• Very short, held in a groove hence, often difficult to see.
• Never longer than body.

Eyes:

• Very small or absent.

Mouthparts:

• For piercing and sucking.

Wings:

• Absent.

Limbs:

• Six legs.
• Hindlegs enlarged and modified for jumping;
• Have claws modified for clinging to feathers and hair.

Abdomen tip:

• Cerci (tails) absent.

Where are fleas found?

• On mammals and birds (rarely) among hairs or feathers.
• Few are found on semi-aquatic animals such as the platypus, but never on marine mammals.

What do fleas do?

• Fleas are external parasites. They can be found alone or in large numbers on suitable hosts.
• When disturbed they jump. They can jump incredible distances.
• They feed on blood.
• They are active during the day.

What looks similar?

• Flies that do not have wings can be mistaken for fleas. Unlike fleas, wingless flies are never thin as if pressed from the sides.
• Lice differ from fleas in that they are flattened as if pressed from above, do not jump when disturbed and can occur on fully aquatic hosts.