COCKROACHES AS HEALTH PESTS
Cockroaches produce odorous secretions form various points in their bodies which can effect the flavor of various foods. Disease-producing organisms such as bacteria have been found in cockroach bodies. Different forms of gastroenteritis appear to be the principal diseases transmitted by cockroaches. These include food poisoning, dysentery, diarrhea and other illnesses. The organisms causing these diseases are carried on the legs and bodies of cockroaches, and are deposited on food and utensils as cockroaches forage. They also carry a wide variety of protozoans and other microorganisms inside their bodies, some of which may occasionally be involved in the spread of disease. Cockroach excrement and cast skins also contain a number of allergens, to which many people exhibit allergic response such as skin rashes, watery eyes and sneezing.
Only a few of the cockroach species found in the United States routinely enter and infest our dwelling. The most common of these are the German cockroach, American cockroach, oriental cockroach, brown-banded cockroach, smokey-brown cockroach, Austrailian cockroach, brown cockroach, woods cockroach, field cockroach, and the Asian cockroach. Of these species the first five represent 95% of all cockroach management in and around buildings.
GENERAL BIOLOGY AND BEHAVIOR OF COCKROACHES
Most cockroaches are tropical or sub-tropical in origin, generally living out of doors. They are mostly active at night, during which time they forage for food, water and mates. May be seen in the day time when a heavy population is present or when some other form of stress is placed on the population (such as lack of food or water). Cockroaches ordinarily prefer a moist environment, and many species also prefer a relatively high degree of warmth. Cockroaches which live in buildings are mostly scavengers and feed on a wide variety of food. They are especially fond of starches, sweets, grease, and meat product; but will also eat a great variety of materials such as cheese, beer, leather, bakery products, starch in book bindings, glue, hair, flakes of dried skin, dead animals and plant materials.
Cockroaches usually choose to live in protected cracks and crevices which provide a warm and humid environment. Cockroaches are not social insects as are the ants and wasps. Cockroaches generally forage individually for food and otherwise behave in a largely individualistic or non-social manner.
A pronotum (a shield-like covering) projects forward over the head; their mouthparts are of the chewing type and are oriented downward slightly toward the rear of their body. With their long spiny legs, they can run rapidly over most surfaces. Specialized pads in their tarsi allow them to easily scale glass windows or walk on a ceiling.
Besides their ability to move around inside and outside, and the fact that some species are good fliers, cockroaches are well known for moving to new areas via “hitchhiking.”
Cockroaches develop by gradual metamorphosis that consists of three stages; egg, nymph, and adult. The female produces a purse-shaped egg capsule, called an ootheca, which has two rows of eggs in it. Nymphs work together to open the seam at the top of the egg. The nymphs resemble the adults in appearance and behavior, but are smaller, do not have wings or wing pads, and frequently have a somewhat different color. Newly molted nymphs are white, but will darken to the normal color within a few hours. Nymphs under a series of molts; with the last molt, the wings are fully developed and he sexes are easily distinguished from each other. The length of time for eggs to hatch, for nymphs to develop, and the life span of adults will vary (within each species) due to temperature, humidity, the quality of their diet, and other environmental conditions.
German Cockroach (Blatella germanica)German Cockroach
It is the most common species in houses, apartments, restaurants, hotels and other institutions throughout the United States.
Adults are pale to medium brown and about ½ to 5/8-inch long. German cockroaches can be distinguished from other roaches by the two dark stripes on the anterior, dorsal portion ( pronotum) of the thorax. The nymph has a light stripe which runs lengthwise down the top of the thorax. Adults of both sexes have well-developed wings, but they never fly. Males are easily distinguished from females by the slender, tapering shape of the abdomen. German cockroach nymphs resemble the adults except that they are smaller, wingless, and darker in color, often being nearly black. A single light stripe running down the middle of the back is the most prominent marking on the younger German cockroach nymphs.
The female carries her egg capsule protruding form the rear of her abdomen until the eggs are ready to hatch. Females which are carrying egg capsules are called “gravid.” The egg capsule is slender and aboutGerman Roach Female with egg 1/3 –inch long and tan in color. Nymphs may open capsule while it is still attached or she may deposit it in some protected place where the young will be able to find food and harborage when they emerge. The German cockroach is the only common house0infesting species that carries the egg for such an extended period of time. Capsules removed from the female more than a couple of days before normal hatching time are unlikely to hatch unless they remain under conditions of very high humidity. This is also true for gravid females which may be killed by an insecticide with several hours, to one day or more, from the time the egg capsule would normally be hatched. The embryos in the egg capsule require a reasonably steady flow of water, usually form the adult female, to prevent death from desiccation or drying out. Again, if the humidity is very high, desiccation may not occur, and the egg capsule can survive for a few hours or longer after premature dropping, or death of the female.
Adult females will usually produce from 4 – 8 egg capsules in their lifetime. Each capsule contains 30-48 eggs. It usually takes 20 -30 days from the time of initial formation of the egg capsule until it hatches. Formation of the next egg capsule usually begins within a couple of weeks.
There are 6 or 7 nymphal stages, called instars, before the molt into the adult stage. Completion of the nymphal stage under room conditions requires 40 to 125 days, depending on environmental conditions (diet quality, crowding, temperatures, etc.). Adult German cockroaches can live up to one year, but most will die from various causes long before that time.
Nymphs have habits similar to the adult. They are active mostly at night and hide in dark crevices mostly at night and hide in dark crevices during the day. If seen during the day, the population is probably so large that the available harborage is already full, or food and moisture are in such short supply that daytime foraging is necessary. This species usually hides in areas close to moisture and food, which means they are generally found in kitchens and other food areas. They prefer to rest on wood than on metal or other smooth surfaces.
The German cockroach is a general feeder, but is particularly attracted to fermented foods and beverage residues (e.g., beer spills). If water is present, adults can live about a month without food, but young nymphs will die of starvation within 10 days. Without food or water, the adults die in less than two weeks. Stressed from lack of food and water will cause the roaches to wander or forage for resources aggressively, even during abnormal period such as the daytime.
If infestations are sometimes found in areas not generally suspected of German cockroaches, for example, dresser drawers in bedrooms, it is usually caused by a very heavy infestation or by the repellent effects of insecticide applications. They will find a food source such as scattered crumbs, soiled clothing, the glue on dresser drawers or on some cosmetic products. If found outside in garage it is also usually due to a heavy infestation indoors.
The German Cockroach is so successful because:
1) has a larger number of eggs per capsule than other species that infest structures.
2) it also has the shortest period to develop form hatching until sexual maturity; thus, populations of German cockroaches will build up faster than other species.
3) nymphs have a better chance of survival than do other species because the female carries the egg capsule during the entire time that the embryos are developing within the egg.
4) Nymphs are smaller than most other cockroaches; thus, they are able to conceal themselves in many places which are inaccessible to individuals of the larger species.
5) In the late 1950’s DDT and chlordane were widely used, and in many cases, some individuals of German cockroach populations exposed to these insecticides survived.
2. American Cockroach – Periplaneta americanaAmerican Cockroach
The American cockroach is also known as the water bug, flying water bug and, in some areas of the South, the palmetto bug. It is the largest of the common species, growing 1 – ½ inches or more in length. It is reddish brown, with pale brown or yellow border on the upper surface of the pronotum. Both the male and the female are fully winged. The wings of the male extend slightly beyond the tip of the abdomen, while those of the female are about the same length as the abdomen.
The female drops her egg capsule with-in a day after it is formed. Can just be dropped indoors, outdoors or it may be glued to some surface with secretions from the female’s moth. Egg capsules are formed at the rate of about one per week until from 15 to 90 capsules have been produced. Each capsule contains 14-16 eggs. At room temperature, nymphs will hatch out in 50-55 days. In the process of hatching, nymphs will molt and leave their first cast skins in the egg case.
Young nymphs are grayish-brown and each will molt 9-13 times before reaching maturity. After the first few molts, nymphs become more reddish-brown in color. The time required to complete the nymphal stage varies from 160-171 days. Under ideal conditions, an adult female can live u to 14-15 months; males live for a somewhat shorter period.
When indoors, the nymphs and adults are usually found in dark, moist areas and basements and crawl spaces as well as in and around bathtubs, clothes hampers, floor drains, pipe chases and sewers. In basements they are usually found in corner areas high on the walls or in floor drains. In the North, this cockroach is commonly associated with steam heat tunnels.
In the South, this roach is abundant in alleyways, yards, hollow trees and palm trees. They especially prefer moist, shady areas. Sometimes found under roof shingles or flashing, or even in the attic. American cockroaches and other outdoor species may move indoors.
American cockroaches feed on a variety of foods, but decaying organic matter seems to be preferred. They also feed upon book bindings, manuscripts, clothing and glossy paper with starch sizing. Syrup and other sweets are also attractive. The adults can survive tow or three months without food, but only about a month without water.
The adults have well-developed wings, but seldom fly. They are capable of gliding long distances and will cover considerable distances if they take off from a tree or roof top. American cockroaches have been reported to fly short distances.
3. Oriental Cockroach – Blatta orientalisOriental Cockroach Male
The oriental cockroach is also referred to as the waterbug, black beetle or shad roach. It is found in all parts of the United States.
Total length of this cockroach is about 1-1/4 inches for the female and 1-inch for the male. The female has small, functionless rudimentary wings called wing pads. The male’s wings cover about ¾ of the abdomen. Neither the male the female can fly. Adults are very dark brown or nearly black, and usually have a somewhat greasy sheen to their body. Females are broader and heavier looking than males.Oriental Cockroach Female
The egg capsule is carried by the female for about 30 hours, after which it is either dropped or attached to a protected surface near a food supply. Females will produce an average of 8 capsules, each containing 16 eggs which will hatch in about 60 days under room conditions.
Nymphs molt from 7-10 times and the nymphal stages usually take several months to one year to complete. The oriental generally has a seasonal developmental cycle. The peak number of adults usually appears in late spring or early summer. The number of adults in the population is generally quite low by the summer and early fall, due to natural mortality and the hatching of nymphs. Few live adults are usually found in the population throughout the year, but if nymphs have not reached maturity by late fall or early winter, their development seems to slow considerably and maturity is not reached until spring.
The nymphs and adults have similar habits and are found associated with decaying organic matter indoors and out. They can be found in yards, beneath leaves, in dumps, in crawl spaces and in the mulch of lower beds. They are also found in high moisture situations such as sewers, drains and dark, damp basements. Both the nymphs and adults are sluggish and are usually located at or below ground level indoors. They are seldom found on walls, in high cupboards or in the upper floors of buildings.
Oriental cockroaches feed on all kinds of filth, rubbish and other decaying organic matter. They seem especially fond of garbage and the contents of discarded tin cans. If water is available, they can live for a month without food, but die within two weeks without water.
Oriental cockroaches are generally found outdoors but if there is a period of drought they will move indoors.
4. Brown-banded Cockroach – Supella longipalpisBrownbanded Cockroach
This is one of the smaller cockroaches, rarely being more than ½ inch long. It is light brown and can be readily distinguished from the German cockroach by the presence of tow lighter, transverse bands running from one side to the other across the base of the wings and abdomen in adult, and in the same position on the nymphs. These bands may be somewhat irregular or broken and are more apparent on the young and the females than on the males. The female has a broader body than the male. Both male and female are both quite active and the adult male fly readily when disturbed. Both adults and nymphs may jump when attempting to escape. Frequently occur in the same buildings as the German cockroach. Professionals must identify this species correctly, as control techniques are different for the two species because of their different behaviors.
A female brown-banded cockroach carries her egg capsule for a day or two, and then attaches it to a protected surface. The egg case is purse-shaped, light brown in color and is cemented in place, usually to the side or under surfaces of infested objects. Females will produce about 14 egg capsules during their adult life, each containing about 18 eggs. These hatch in 50-75 days, depending on temperature. Under room conditions, nymphs mature in about 160 days. Adults may live up to 10 months.
Nymphs and adult are generally found on ceilings, high on walls, behind picture frames and light fixture, or near motors of refrigerators and other appliances. They are also found in light switches, closets and appliances. They are also found in light switches, closets and furniture. They do not require as close an association with moisture sources as the German cockroach. This helps explain why they are founding other rooms other than the kitchen area and bathrooms. These cockroaches dislike light and are not normally seen during the day.
The brown-banded cockroach prefers feeding on starchy materials. However, they can be found feeding on almost anything, and have been known to chew on such non-food materials as nylon stockings (presumably for the residues of body oils and skin flakes).
When looking for brown-banded during an inspection, look beneath tables and chairs, dressers and chests. Look also behind pictures, and picture moldings, on rough plaster walls and ceilings, and most especially on the ceilings and upper walls of cabinets, pantries and closets.
5. Smokey-brown Cockroach – Periplaneta fuliginosaSmokeybrown Cockroach
Smokey-brown cockroaches are closely related to the American cockroach but are distinguished by their smaller size, being slightly more than 1-inch long, and uniform mahogany brown color. They do not have any lighter coloration around the edge of their pronotum, as does the adult American cockroach. Both males and females have wings longer than females have wings longer than their bodies. Young nymphs have long antennae which are white at the tip.
Females lay a dark-brown to black egg capsule which contains 24 eggs. The capsules are firmly attached to some object, although occasionally they may be found lying loosely on the ground or floor. Each female produces about 17 capsules. The smokey-brown cockroach will live for about 200 days at room temperature.
Normally, this cockroach feeds on plant material, but it can feed on almost anything that other cockroach species feed on more inside a dwelling. It is commonly found living in decaying wood shingle roofs and in gutters where it feeds on decaying organic matter. In attics, they are typically found living at the roof line.
Nymphs are usually brought into the house. They can enter around doors and windows, through ventilation ports under the eaves of a house or any other small cracks or crevices which lead inside.
6. Woods Cockroach – Parcoblatta spp.Woods Cockroach
Woods cockroaches are small, usually not more than 2/3 inch long. Adults are dark brown with the sides of the thorax and the front half of the wings margined with yellow. In the male, the wings are longer than the body, while those of the female cover only 1/3 to 2/3 of the abdomen. The males are generally strong fliers, whereas the females do not fly.
Egg capsules are produced during the warm months and are deposited loosely behind the loose bark of dead trees, fallen logs or stumps. The woods cockroach rarely breeds indoors. The nymphs and adults are usually found outdoors beneath loose bark in wood piles, stumps and hollow trees.
Usually becomes a problem when firewood is brought indoors. They can be especially troublesome during the mating season, which is often May and June. Male wood cockroaches are strong fliers and will come from considerable distances, often in large numbers. They are readily attracted to lights at night, and accidentally gain entry indoors. Woods cockroaches feed primarily on decaying organic matter.
7. Australian Cockroach – Periplaneta australasiaeAUSTRALIAN COCKROACH
The Australian cockroach is rarely more than 1-1/4 inches long. It is reddish-brown and can be distinguished by prominent yellow stripe along the outer front edge of either wing, and by a prominent dark spot in the center of the pronotum.
Adult females drop their egg capsule in a crack, crevice or other hidden area shortly after it is formed. The eggs hatch about 30 days after the egg capsule is dropped. There are approximately 24 eggs per capsule, but only about 2/3 this number usually hatch. Egg capsules are dropped at about 10-day intervals.
The nymphs are strictly marked with distinct splotches of yellow on the dorsal side of the thorax and abdomen. Nymphs move about under loose dark and in moist decaying vegetation, as do the adults.
It feeds predominantly on plant materials, although it will feed on various starchy materials in homes.
8. Brown Cockroach – Periplaneta brunnea
The brown cockroach resembles the American cockroach except it has a broader body and less distinct markings on the thorax. The last segment of the circus is short and blunt, when compared to that of the American cockroach. Brown cockroaches occur indoors and outdoors, where they are found under bark of trees, in sewers, crawl spaces and similar places. The brown cockroach normally feeds on plant materials.
Egg capsules contain an average of 24 eggs each. The egg capsule is normally glued on a wall near the ceiling, usually in open places in either homes or commercial buildings. Indoor, it seems to prefer sticking the egg capsule to cement or plaster, rather than wood. Outdoors, placement of the egg capsules is similar to that of the American cockroach, in decaying wood.
9. Field Cockroach – Blattella vaga
This is a small cockroach, slightly smaller than the German cockroach, less than ½ inch long. Can be distinguished by a blackish area on the front of the head, extending from the mouthparts to between the eyes. The field cockroach feeds largely on decomposing vegetation and is common in irrigated areas. It normally lives outdoors occupying areas under stones, clumps of earth and similar locations. Occasionally, however, it wanders into homes during dry parts of the year.
The egg capsules are carried by the female until they are ready to hatch. The capsules are normally dropped outdoor. If found indoors, they wander about on walls and floors and make no attempt to hide in dark cracks, as German cockroaches do.
10. Asian Cockroach – Blattella asahinaiAsian Cockroach
Has been introduced through the Port of Tampa. It is similar to the German cockroach, but has very different behavior. It prefers to infest shaded and moist areas in the landscape, grassy areas and groundcovers. Adults will fly quite readily and for relatively long distances. They will fly to lights at night. Because they will enter homes, they are a particular nuisance when they fly inside (into TV screens, onto people, etc.). Also when they fly into backyard BBQ’s and other patio events.
The presence of cockroaches is often detected by their damage, or by the fecal matter (called “frass”) they deposit. The size and shape of the fecal matter is a clue to the type of cockroach. The size and shape of the mandible marks are helpful in determining the type of cockroach has done damage.
Far more food is contaminated by cockroaches than they are able to eat. Diseases are transmitted as a result of these habits.
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