Cockroaches: what is known and what is uncertain about one of the most hated pests in the world

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One of the most hated insects in the world, cockroaches are cosmopolitan, found in the most diverse environments on the planet. Most species are of tropical or subtropical origin.

Household cockroaches are those that live in or around homes and other human-built structures, including outbuildings such as grease traps, sewers, manholes, and other damp, dark places.

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Studies of cockroach fossils demonstrate that these insects have changed little over the course of evolution. Therefore, it is considered one of the most adaptable and resistant species in the animal kingdom, being able to adapt to the most varied environmental conditions.

Although they are considered disgusting, cockroaches are insects of reduced medical importance when compared to other disease-carrying insects. Unlike mosquitoes, cockroaches do not carry disease-causing agents inside their bodies, but they can carry bacteria and other harmful microorganisms as they circulate through various types of dirty places.

urban pests

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Scientific interest in cockroaches is relatively recent. The sewage cockroach is used in schools and universities as a study model on the anatomy and physiology of insects, in entomology.

In addition, they play a significant role in understanding mechanisms of resistance to insecticides, being kept in the laboratory for studies, with this purpose, since the 1940s.

In addition to the scientific interest, such insects have a significant potential for transmission of disease-causing microorganisms, as they carry these agents from contaminated sites, such as garbage and sewage, to food and utensils used by humans.

The microorganisms contained in the substrate that adhere to the cockroach’s body, mainly in the hair and bristles of the legs, are mechanically transported from a dirty point to a clean one. Mechanical transmission also occurs through the waste released by cockroaches.

Not long ago, their role as vectors of disease agents was questionable, as it was alleged that cockroaches represented just one more factor in an environment without sanitation, with other basic causes for the occurrence of diseases. Today, however, based on some epidemiological events, cockroaches already figure as a relevant intermediary in outbreaks of diarrhea and are increasingly related to occurrences of allergies.

To prevent the proliferation of cockroaches, it is essential to maintain a clean environment. Avoid leaving food on display in the kitchen and food scraps on the floor. Drains must be sealed or closed. The use of insecticides can be a punctual alternative in the case of few cockroaches. In the face of an infestation, it may be necessary to call a specialized fumigation service.

Different types of cockroaches

The shape and size vary depending on the species. In some species, males have wings, while females do not.

The antennae play a fundamental role in the survival of the insect, serving not only as a direction element, but also to capture vibrations in the air or
still smell food or pheromones.

The oral apparatus is chewing, enabling them to gnaw paper, clothes soiled with food, hair, paint, honey, bread, meat, potatoes and fats. Some feed on wood (cellulose). They are particularly attracted to sweet, fatty and animal foods. However, they can feed on cheese, beer, creams, bakery products, glues, hair, sloughed skin cells, corpses and vegetable matter.

Although they are not social animals like bees, termites and ants, cockroaches can be found in groups. Cockroaches are nocturnal animals, when they leave the shelter to feed, reproduce, lay eggs and fly. During the day, they are sheltered from light and the presence of people. Some special conditions contribute to its diurnal appearance, such as overcrowding and lack of food or water.

Get to know different species of cockroaches, according to the booklet by the Laboratory of Entomological Biodiversity at the Oswaldo Cruz Institute (IOC/Fiocruz).


The French cockroach (Blattella germanica) is found indoors, with humid and warm areas, around 32°C, preferring crevices close to food and water sources in bathrooms and kitchens.

It is small, reaching 1.2 to 1.5 cm in length, brown to black in color. It has a nymphal development period of 6 to 12 weeks, and lives 6 to 9 months. It doesn’t usually fly, even though it has wings.


The eastern cockroach (blatta orientalis) prefers decaying food, is cold tolerant, and prefers humid areas with temperatures below 29°C. It is often
Found in bark and leaves of fallen trees around buildings.

From dark brown to black, a striking feature of the species is its male measures approximately 1.8 to 2.9 cm in length, with a pair of wings that cover two thirds of the abdomen and a narrow body.

The female, in turn, measures about 2 to 2.7 cm in length, has small, colorless wings and a bulkier body. The male is capable of short flights, with distances between 2 to 3 meters.

of sewer

The well-known sewage cockroach (american periplanet) requires a source of water and prefers fermented foods. It can be found in sewers and basements, particularly around drains and pipes.

They prefer temperatures around 29°C and do not tolerate cold. They are reddish brown and large, measuring approximately 3.4 to 5.3 cm, with long wings, although they are not very good fliers.

(With information from the Journal of USP)

Source: CNN Brasil

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