Blatta orientalisOriental cockroach

Geographic Range

Blatta orientalis, the Oriental Cockroach, is common world-wide. There is no country that is free of the presence of this insect. Combined with Blatta germanica, the Oriental Cockroach is present in approximately ten per cent of properties in areas all over the world (Cornwell 1968). Despite their name, Blatta orientalis is thought to have originated in Africa.


The Oriental Cockroach is found both outdoors and indoors. It can be found outside during warm weather in trash cans, sewers, or even under old leaves or stones. In Asia it has been found in caves where bats live. During autumn, however, Oriental Cockroaches may move in large groups into unheated buildings, since they prefer a cooler environment. The preferred temperature ranges from about twenty to twenty-nine degrees Celsius. It is more unlikely to find Blatta orientalis in higher level floors on buildings. Most likely it will be found in the first floor of a building. It likes damp areas and will live in damp basements, near water pipes, leaky drains, or any similar areas (Cornwell 1968; Lyon 2000, Ogg et al. 1996).

Physical Description

The adult Oriental Cockroach is a shiny black or dark-brown color. The younger members are darker and not shiny like the adults. The male of Blatta orientalis is smaller than the female. Males are about 2.6 centimeters in length, while females tend to be from 2.6 to 3.25 centimeters in length. The average male weighs approximately .45 grams while the female weighs .95 grams. The male is also more slender than the female, whose abdomen is broad in comparison to his. Another difference between the male and female of the species is that while the male has wings that almost reach the abbomen, the female only has pads as her wings. Although both have wings or pads, neither can fly. The nymphs have a similar shape to the adults, but unlike the adults, are wingless (Cornwell 1976; Lyon 2000).

  • Range mass
    .45 to .95 g
    0.02 to 0.03 oz


The female of the species Blatta orientalis produces from one to eighteen red/brown egg cases during her life: about one case per month. These cases are about 1 cm long, .65 cm wide, and contain an average of fourteen eggs. They can, however, contain up to sixteen eggs each. A capsule is carried by the female cockroach anywhere from twelve hours to five days until she places it somewhere where there is food and warmth. It is also very important to place them somewhere where they will be safe. The female of this species, unlike some other roach species, does not help her offspring. After she deposits the eggs, it takes about two months for them to hatch, but it takes approximately twelve months for the nymphs to be fully developed. Most of these roaches are adults when fall comes, but the adults live only from one to six months (Lyon 2000; Bull's Pest Control, Inc. 1999, Ogg et al. 1996).


The Oriental Cockroach is most common in May, June, and July. The adult is active during the spring, and the nymph from March through most of the summer. During this period the nymph casts its skin from seven to ten times. This species is found in groups, like the other species of cockroaches, but is more sluggish. The female almost "drags" her abdomen along the floor when she walks, while the male keeps his body completely above the ground. Unlilke other roaches, the male is very direct when approaching the female for mating, and the female is calm in return. The male raises his wings during the process of mating, while the female moves her mouth parts over the male's dorsum. Although the female is above the male at the beginning, at the end, they are positioned end to end for copulation. Only one in twenty matings, are successful (Cornwell 1968; Lyon 2000; Bull's Pest Control Inc., 1999 Ogg et al. 1996).

Food Habits

This species is an omnivorous one, meaning that it eats animals, plants, or anything that is available for it to consume. Since Blatta orientalis does not have mouthparts that are specialized to eat certain things, it can eat hard or soft materials and can drink any kind of liquid. However, it mostly feeds on garbage or any sort of decaying organic matter, although its favorite foods consist of anything that is either sugary or starchy. This cockroach invades homes and eats whatever is left out, which poses a danger because it can contaminate the food that it touches, leaving infectious material for the human living in that home. This cockroach can survive one month without eating, as long as it consumes water. If there is no water, then fresh fruits are a good source of liquid for it to drink. However, it will die in two weeks if it is not provided with either food or water (Cornwell 1968; Lyon 2000).

Economic Importance for Humans: Positive

No known benefit.

Economic Importance for Humans: Negative

Blatta orientalis is thought by many to be the dirtiest of pests that invade and infest homes. This roach can ruin food and also produces a smelly odor. By moving back and forth between garbage and human food, it contaminates the food with diseases that can lead to many illnesses, including food poisoning, dysentery, diarrhea, and others. It is also believed that exposure to roach waste and skin fragments in the air is a cause of some cases of childhood asthma. It is considered to be the 6th worse pest in the world (Cornwell 1976; Lyon 2000).

Conservation Status

Blatta orientalis is anything but endangered. In fact, there are various measures being taken in order to rid the world of this species. The Oriental Cockroach is unwanted everywhere. In order to rid themselves of it, people should to keep their homes clean, reduce the food that is available to it, use chemical control (including aerosols, dusts, etc), and place sticky traps in order to control those that are indoors (Ogg et al. 1996 ).

Other Comments

The species Blatta orientalis, the Oriental Cockroach, is also known as the black beetle or the water bug. It is very common all over the world, and is the most common urban roach in England. Because of the danger that it poses, people try to eliminate it. One of the methods used to get rid of the cockroach is to use insecticides. However, this roach has a resistence to certain insecticides and because there are so many roaches, it is difficult to exterminate them (Ogg et al 1996, Bull's Pest Control, Inc. 1999).


Gladys Rodriguez (author), University of California, Irvine, Rudi Berkelhamer (editor), University of California, Irvine.



Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map


living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map


living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.


found in the oriental region of the world. In other words, India and southeast Asia.

World Map


Bull's Pest Control Inc., 1999. "Oriental Roaches" (On-line). Accessed October 27, 2000 at

Cornwell, P. 1976. The Cockroach vol. 2. Great Britain: The Pitman Press.

Cornwell, P. 1968. The Cockroach vol.1. Great Britain: Anchor Press.

Lyon, W. 2000. "Ohio State University Fact Sheet" (On-line). Accessed October 27, 2000 at

Ogg, B., D. Ferraro, C. Ogg. 1996. "Cockroach Control Manual (online)" (On-line). Accessed 26 March 2001 at

Urban Pest Control Research Center, 1998. "Oriental Cockroach" (On-line). Accessed October 27, 2000 at