The Dreaded Cockroach
The most common pest varieties found in Australia are the
American, German, Smoky Brown and Oriental Cockroach
s. American cockroaches are large and brown to dark brown in colour with a pale flash on the ‘shoulders’. The smoky brown is generally a darker colour and lacks the pale shoulder flash. German cockroaches are smaller and brown in colour. Oriental cockroaches are medium sized and dark brown to black in colour. Cockroaches aren’t picky eaters and will consume just about anything, ranging from food spills on a kitchen floor to our garbage. They harbour and transmit disease pathogens and can spread a number of diseases including Salmonella and gastroenteritis. After feeding on contaminated food, disease bacteria can remain in the cockroach digestive system for a month or more and are passed to us in its droppings where Salmonella bacteria can survive for several years. Cockroaches will vomit and defecate on food, and it is known that disease may be transmitted to humans when humans eat food contaminated by cockroaches. Food and utensils can also become contaminated with cockroach faeces. Recent studies have indicated cockroaches can also cause allergies. Many people who are allergic to house dust are also allergic to cockroaches. Crushed cockroach body fragments and faeces can be a major constituent of house dust.
Species includes: German cockroach, American cockroach, Smoky brown cockroach, Oriental cockroach,
American cockroaches are one of the largest cockroaches that invade homes. Adults can be slightly more than 50 mm (5 cm) long.
Adult American cockroaches are reddish brown or mahogany colored. The area behind their heads is outlined with a yellow band. Immature American roach nymphs are grayish brown. As they mature, their color becomes more reddish brown.
Both male and female American cockroaches can fly. The wings develop when the roaches become adults.
Behavior & Diet
American cockroaches normally live outdoors. They prefer warm, damp areas like flowerbeds, and under mulch. In many parts of the United States people call them “palmetto bugs” because they live on trees. American cockroaches are very common in sewer systems of many American cities.
American cockroaches enter homes to find water or food. They can easily pass under doors if the weather stripping is damaged. Basement windows and garages are also common entryways. When American cockroaches enter homes, they often go to bathrooms, kitchens, laundry rooms and basements.
Outdoors, American cockroaches eat leaves, tiny wood particles, fungi and algae. They also eat small insects. Indoors, American cockroaches forage under appliances, in drains, in kitchen cabinets and on the floor. They eat crumbs, scraps of food and spilled food that they find. They will also eat pet food that is left out overnight.
Female American cockroaches make protective cases for their eggs. These cases are capsule-shaped. After forming a capsule, the roach deposits it in a warm, humid area. An average American roach egg capsule contains about 16 eggs.
When the eggs hatch, the tiny nymphs come out of the capsule. As they grow, the immature roaches shed their skins. If there is plenty of food, American cockroaches can develop from egg to adult in as little as 5½ months.
Signs of American Cockroach Infestation
Homeowners may see these active cockroaches. American roaches can run very fast, and they usually scurry into a dark area. If they are startled, American roaches may even fly.
American cockroaches leave their droppings in the dark areas where they hide. Homeowners may find these droppings in basements, in pantries or behind appliances.
American cockroach droppings are small, and sometimes people mistake them for mouse droppings. American cockroach droppings have ridges on the sides and they are blunt on the ends. Mouse droppings have pointed ends. Since mice groom themselves, mouse droppings often have hairs embedded in them.
American cockroach egg cases are about 38 mm long. They are dark-colored—reddish or blackish brown. Homeowners often find these egg cases in basements, in laundry rooms or kitchens. The egg cases may be under cabinets or behind appliances. American cockroaches also deposit their egg capsules behind stored items in garages and sheds.
Cockroaches produce a chemical called an “aggregation pheromone.” The odor of this chemical causes the roaches to stay together in groups. Some people describe the odor of these pheromones as having a “musty” smell. As the roach population starts to grow, people with sensitive noses may begin to notice this odor.
German cockroaches are well-known indoor cockroaches with a distribution that is world-wide. Adults are easily recognized by their light brown or tan coloration with two black horizontal stripes located on the pronotum immediately behind the head, and growing to a length of 13-16 mm. The much smaller young, or nymphs, are darker, almost black in color, also with the black stripes behind the head.
While adult German cockroaches have wings, they rarely fly, preferring to run.
Behavior, Diet & Habits
Although capable of living outdoors in tropical environments, German cockroaches are most commonly found indoors, with a preference for
the warmer and more humid areas of a structure. In homes, these insects will typically be found in kitchens and bathrooms, but can move to other areas of a home if food and moisture are available.
In most cases, German cockroaches are introduced into a structure or residence when bags, boxes or cardboard containers are brought into the home. They may even be brought in with used appliances. In multiunit apartment buildings, German cockroaches can easily move between units, using the shared plumbing and pipes as a highway.
German cockroaches are scavengers, capable of feeding on most any food source available, including toothpaste, soap and the bindings of books. These pests are known for their ability to capitalize on the availability of even the smallest amounts of food by feeding on crumbs missed during cleaning or feeding on the dirty dishes left in the sink overnight.
German cockroaches are known for their ability to reproduce quickly. Female German cockroaches only need to mate once for the production of young. After mating, and under normal conditions, they will produce, on average, 4 to 6 egg cases during the course of their lives, with each egg case, or ootheca, containing approximately 30 to 40 eggs. This egg case is then carried by the female until 1 to 2 days before hatching. Depending upon the conditions, the average time for development, from egg to adult can range from 54 to 215 days, with an average of approximately 100 days. As adults, German cockroaches can survive anywhere from 100 to 200 days.
Signs of a German Cockroach Infestation
German cockroach droppings may appear as small, dark, “pepper-like” material left on countertops or in drawers. Fecal staining may appear as dark spots or smears, some that are slightly raised, in the corners of rooms, along the tops of doors or around small cracks and openings into walls.
Since German cockroach females carries their egg case until 1 to 2 days before depositing it, empty egg cases may be found in areas that the females frequent.
German cockroaches are also known to secrete a number of odorous compounds. When populations are present in large numbers, it may be possible to detect a mild, or what some have reported as a “musty” odor.
German Cockroach Life Cycle
German cockroaches are one of the most common cockroach species found in households. German cockroaches undergo three distinct life
phases: egg, nymph and adult. Their entire life cycle spans approximately 100 days, although this is dependent on factors such as temperature, diet and injuries.
German cockroaches breed continually. In a lifetime, a female cockroach is capable of producing almost 400 eggs. Populations grow quickly in optimal conditions. A typical thriving population is comprised of 75 percent nymphs and 25 percent adult roaches.
German cockroaches begin life as eggs within an egg casing known as an ootheca. The oothecae contain approximately 35 eggs and are brown in color. Oothecae are approximately 7 mm long and 2 mm wide. They are very resilient and can survive harsh conditions.
Female German cockroaches carry the oothecae attached to their abdomens until about two days prior to hatching and then deposit them in a protected location. Oothecae may be seen protruding from the abdomens of German cockroach females. Nymphs emerge from the oothecae as tiny insects. They gradually darken into dark brown or black cockroaches with parallel lines visible upon the pronotum. German cockroach nymphs are wingless and incapable of reproduction. Nymphs molt six to seven times and can develop completely within 100 days under optimal conditions.
The adult stage begins with the last successful molting. At this point, German cockroaches are approximately 15 mm in length and are winged. Adult German cockroaches are nocturnal insects that hide during the day and scavenge at night. Despite their fully developed wings, German cockroaches very rarely fly.
German Cockroach Nymphs
Female German cockroaches create egg pouches known as oothecae. These oothecae remain attached to the female’s abdomen until they are nearly ready to hatch.
German cockroach nymphs resemble adults. However, nymphs are much smaller, do not have wings and are incapable of procreating. As they grow, nymphs shed their exoskeletons several times.
These nymphal stages span approximately 100 days. After the final molt, German cockroach nymphs are fully developed, winged adults equipped with reproductive capabilities.
German cockroach nymphs are similar to the adults of their species. Often mistaken for albino cockroaches, newly molted individuals are
white in color. However, the white cuticles covering their bodies gradually darken and harden. German cockroach nymphs may consume their cast-off skins as food. Eventually the nymphs will be dark brown or black in color and characterized by a single, light stripe that runs the length of the back.
German cockroaches are primarily active at night and hide in crevices during the day. Because of their size, German cockroach nymphs are able to hide in places that are inaccessible to larger cockroaches. Under optimal conditions and at room temperature, German cockroach nymphs can complete development within 100 to 200 days.
German cockroach nymphs also emit collective pheromones through their feces. This increases aggregation within their populations. As the population grows, the smell of the pheromone can become noticeable. This musty smell is a sign of infestation.
Smoky Brown Cockroach
The smokybrown cockroach is a common pest of the southeastern Unites States. Although mainly found from central Texas eastward, and as far north as North Carolina, the smoky-brown cockroach also has been found as far north as Indiana and Illinois. This primarily outdoor pest gets its name from its uniform brownish-black coloration and, as adults, can reach a length of 38 mm. These strong fliers have wings that extend beyond their body.
Behavior, Diet & Habits
Outdoors, smokybrown cockroaches can be found in areas that are warm, very moist and protected from the elements. Since this insect is prone to dehydration, the availability of a moist environment is critical for
its survival. Around homes and structures, the smokybrown cockroach can be found in tree holes and cavities, beneath mulch beds and ground cover, and around soffits and eaves, or areas where moisture problems may exist. The smokybrown cockroach can easily penetrate buildings through openings or gaps beneath siding, through attic or soffit vents, openings around utility and plumbing penetrations, and through open windows or doors.
Smokybrown cockroach feeding activity is most evident during the late dusk or early dawn hours when the insects leave their hiding places in search of food. These opportunistic feeders will utilize any food that may be available, including human food scraps, dead insects, fecal matter and even plant materials. It is also not uncommon to see these insects taking a drink when water is available.
Dependent upon environmental conditions, the development time for a smokybrown cockroach, from egg to adult, can vary greatly, with a range of 160 days to 716 days. As adults, a female smokybrown lives an average of 218 days, and a male will live, on average, 215 days. During her lifetime, a female will produce an average of 10 egg cases, or ootheca, with an average of 20 eggs per case. These egg cases are then attached to a protected surface within a day of production, where they will remain until the young hatch.
Signs of a Smokybrown Cockroach Infestation
Smoky Brown cockroaches are a more regionally important species, impacting the southeastern United States. These insects are commonly found outdoors and can be seen primarily at night, walking in search of food around landscaping beds, running in and out of ivy or other ground cover, and in and around gutters and fascia of homes and structures. These insects then become a pest when, attracted by interior lights, they gain entry into a home or structure through openings in windows, doors and other gaps into the home.
Fecal material and droppings can be evident in areas that the smokybrown cockroach frequents.
Attached to a surface within a day of production, the 11 to 14 mm long, dark-brown to black egg case, or ootheca, may be observed in areas that the smokybrown cockroach frequents.
Although smokybrown cockroaches are related to the American cockroaches, they are slightly smaller in size and uniformly mahogany in color. Nymphs are the same color as adults and their antenna tips are white. Smokybrown cockroaches can grow up to 38 mm in length. Both sexes have wings that are longer than their abdomens. Smokeybrown cockroaches are capable of flying, and they are attracted to light.
Their oothecae, or egg capsules, hold an average of 20 eggs. Each female is capable of producing up to 32 oothecae in one lifetime. Nymphs undergo several molting stages, after which they emerge as adults. The life span of smokybrown cockroaches averages over a year, although they can live as long as 2 years or more under ideal conditions.
While smokybrown cockroaches prefer to eat decaying plant matter, they will consume any food source available to them. They are nocturnal and hide in small places during the day, making themselves inaccessible to humans and predators. Commonly found in tree holes, wood-shingled roofs and in gutters, smokybrown cockroaches thrive in damp, dark and poorly ventilated areas. Inside, they breed in attics, where their populations can grow unnoticed.
They prefer nondwelling areas such as greenhouses, nurseries and gardens but can be an indoor pest. They can be found throughout Australia.
Shiny black to a dark reddish-brown color, oriental cockroaches are a pest invader that most frequently gains entry beneath the thresholds of doors, through open doors or gaps beneath siding, even following utility lines, pipes, open drains or sewers into a structure or home. The adults of the oriental cockroach are very different in appearance. The smaller adult male oriental cockroaches, reaching only a length of 25 mm, can be identified by the presence of three-quarter-length wings, leaving the last few abdominal segments exposed. The larger adult female oriental roaches, reaching a length of 32 mm, on the other hand, lack wings altogether, having only large wing pads that cover the first couple of segments of the body. Neither the male nor female is capable of flight.
Behavior, Diet & Habits
Primarily an outdoors species, oriental cockroaches are well adapted for surviving in the natural environment. Most outdoor populations can be found living beneath the mulch in landscape beds, in leaf litter, beneath stones or debris outdoors. If access is available, the insects can thrive in the voids or openings beneath porches, in wall voids and crawlspaces. In more metropolitan areas, oriental roaches can be found in large numbers living in storm drains and sewers.
Oriental cockroaches are known for their preference of feeding on garbage, filth or material that has begun to decay. These cockroaches are very dependent upon water. While studies have shown that they can
survive for up to a month without food, these insects can not survive for more than two weeks without water.
On average an adult male oriental cockroach will live 110 to 160 days, whereas the adult female can live anywhere from 35 to 180 days. During that time, a single female oriental roach can produce approximately eight egg cases, or ootheca, with approximately 16 eggs per case. Approximately 30 hours after she has produced the egg case, she will drop it in a protected area where it will stay until the young hatch. The development time for the oriental cockroach is greatly affected by the season. In the warmer months, the time needed to develop from an egg to an adult may take as few as 200 days. However, when the weather becomes colder, or during the late fall and winter months, it can take as many as 800 days for the cockroaches to go from egg to adult.
Signs of an Oriental Cockroach Infestation
During the warmer months, it is not uncommon to find oriental roaches outside around landscaping beds, congregating beneath moist gutters, or even scurrying out from storm drains and sewer grates at night. Mostly active at night, they can be found during the day in areas and rooms that are kept primarily moist, dark and undisturbed.
Egg cases, or oothecas, of the oriental cockroach may appear dark brown or reddish in color and almost 8 to 10 mm in length. Each egg case, which can hold approximately 16 eggs, is dropped by the female into protected areas, almost 30 hours after it is produced.
In areas where large populations of oriental cockroaches are present, a musty odor can be detected. This odor is a result of chemicals that are secreted by the insects that are used to communicate within the population.
Oriental Cockroach Nymphs
Oriental cockroach egg cases, or oothecae, are dark and reddish-brown in color. Measuring approximately 8 to 10 mm in length, they appear to be slightly inflated. Each female is capable of producing between one and 15 oothecae, which contain approximately 16 eggs each. Females deposit the oothecae in sheltered, protected locations near food and water supplies. Oriental cockroach nymphs appear extremely similar to adults of their species. Female nymphs are broader and heavier than male nymphs. The nymphal stage spans approximately one year, during which time Oriental cockroaches molt several times.
Nymphs also exhibit habits similar to those of adults. Whether inside or outside, they are found near decaying organic matter. In yards, they hide well beneath leaves and the mulch of flowerbeds. They can also thrive in high-moisture areas such as sewers, drains and basements. Both
nymphs and adults of this species are sluggish and tend to prefer below-ground-level indoors.
Oriental cockroaches observe a seasonal developmental cycle. They seem to develop more quickly during the rainy part of the year. The peak of adult population is in late spring or early summer and slows considerably by late summer and into early fall. If nymphs have not yet reached maturity by the fall, they will usually not become adults until spring.
The life cycle of a cockroach
A female cockroach lays between 10 and 40 eggs at a time. On average, the female can lay around 30 batches of eggs in her lifetime. The hatched young look the same as adult cockroaches, but smaller and without wings. Depending on the conditions and type, a cockroach can live for up to 12 months. These insects are cold-blooded and thrive in warm, humid conditions. This is why buildings in the northern parts of Australia are particularly prone to infestations.
Common hiding spots for cockroaches
Cockroaches prefer to live in kitchens and other food preparation areas, so they can feed off food spills and have access to water. Hiding spots for the household cockroach include:
Cracks in walls.
Confined spaces, such as behind the refrigerator, in a pantry or underneath a stack of magazines, newspapers or cardboard boxes.
Any furniture items that are generally left undisturbed.
Around water heaters.
In drains and grease traps.
Treating the house yourself
Some general suggestions to eliminate cockroaches yourself include:
Thoroughly clean the house at least weekly.
Pay special attention to the kitchen and other food preparation areas.
Clean regularly underneath the fridge, stove, toaster and other movable appliances.