Cockroaches are one of the most commonly noted household pest insects. They feed on human and pet food and can leave an offensive odor. They can also passively transport microbes on their body surfaces including those that are potentially dangerous to humans, particularly in environments such as hospitals. Cockroaches are linked with allergic reactions in humans. One of the proteins that triggers allergic reactions is tropomyosin. These allergens are also linked with asthma.
The German cockroach (Blattella germanica) is a small species of cockroach, measuring about 1.3 to 1.6 cm (0.51 to 0.63 in) long; however, larger individuals have been recorded. It can be tan through brown to almost black, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is unable to sustain flight. Found throughout many human settlements, these insects are particularly associated with restaurants, food processing facilities, hotels, and nursing homes. In colder climates, they are found only near human habitats, since they are not very tolerant to cold. However, German cockroaches have been found as far north as Alert, Nunavut, and as far south as southern Patagonia. The German cockroach is originally from Africa. It is very closely related to the Asian cockroach, and to the casual observer they appear nearly identical and may be mistaken for each other (the Asian cockroach, however, is attracted to light and is capable of flight not unlike a moth— not so of the German cockroach). Though nocturnal, this cockroach can be seen in the day occasionally, especially if the population is large or they have been disturbed. However, sightings are most commonly reported in the evening hours, as they are most active at night. This type of cockroach can emit an unpleasant odor when excited or frightened.
The oriental cockroach (Blatta orientalis), also known as the waterbug, is a large species of cockroach, adult males being 18–29 mm (0.71–1.1 in) and adult females being 20–27 mm (0.79–1.1 in). It is dark brown to black in color and has a glossy body. The female Oriental cockroach has a somewhat different appearance to the male, appearing to be wingless at casual glance but has two very short and useless wings just below her head. She has a wider body than the male. The male has long wings, which cover two thirds of the abdomen and are brown in color, and has a narrower body. The odd male is capable of very short flights, ranging about 2 to 3 meters. The female oriental cockroach looks somewhat similar to the Florida woods cockroach, and may be mistaken for it. Originally endemic to the Crimean Peninsula and the region around the Black Sea and Caspian Sea, its distribution is now cosmopolitan.
The oriental cockroach tends to travel somewhat more slowly than other species. They are often called "waterbugs" since they prefer dark, moist places. They can often be found around decaying organic matter, and in sewers, drains, damp basements, porches, and other damp locations. They can be found outside in bushes, under leaf groundcover, under mulch, and around other damp places outdoors. They are major household pests in parts of the northwest, mid-west, and southern United States.
The Asian cockroach is nearly identical to the German cockroach (Blattella germanica) except for a few minor morphological differences. Like the German cockroach, it is about 1.6 cm (0.63 in) long, is tan to brown in color, and has wings. However, its wings are longer than the German cockroach, and there is a difference between a groove in the abdomen between the two species. There are other differences. The quickest way to tell the difference between the two species is that the Asian cockroach is a strong flyer (almost like a moth) and is attracted to light, unlike the German cockroach. This species tends to prefer the outdoors, whereas the German cockroach prefers living indoors.
The brown-banded cockroach, Supella longipalpa, is a small species of cockroach, measuring about ⅝ in (10 to 14;mm) long. It is tan to light brown. It has two light-colored bands across the wings and abdomen, they may sometimes appear to be broken or irregular but are quite noticeable. The bands may be partly obscured by the wings. The male has wings that cover the abdomen, while the female has wings that do not cover the abdomen completely. The male appears more slender than the female, the female appears wider.
The brown-banded cockroach has a fairly wide distribution, being found in the northeastern, southern, and midwest regions of the United States quite commonly. They are one of the most recent alien cockroaches to form breeding colonies in Britain and Ireland. They need less moisture than the German cockroach so they tend to be more broadly distributed in the home, such as in living rooms and bedrooms. They can often be found in homes and apartments, but are less common in restaurants. They tend not to be found in the daytime, since they avoid light.
The American cockroach (Periplaneta americana), also colloquially known as the waterbug, but not a true waterbug since it is not aquatic, or misidentified as the palmetto bug, is the largest species of common cockroach, and often considered a pest. It is also known as the ship cockroach, kakerlac, and Bombay canary.
Despite the name, none of the Periplaneta species are endemic to the Americas; P. americana was introduced to the United States from Africa as early as 1625. They are now common in tropical climates because human activity has extended the insect's range of habitation, and are virtually cosmopolitan in distribution as a result of global commerce.
Although closely related to the American cockroach (Periplaneta americana), the smokybrown cockroach is readily distinguishable from it by its uniformly dark brown–mahogany coloration. Furthermore, unlike the American cockroach, which possess a light-rimmed pattern on its thorax, the smokybrown cockroach's thorax is dark and shiny.
The smokybrown cockroach is a detritivore and can feed off a wide array of organic (including decaying) matter. Like most cockroaches, it is a scavenger. It tends to lose more moisture than its relatives and requires water every 2–3 days.
The smokybrown cockroach may come indoors to look for food and even to live; generally, however, in warm weather, it will move outdoors.
The Australian cockroach (Periplaneta australasiae) is a common species of tropical cockroach, with a length of 23–35 millimetres (0.91–1.4 in). It is brown in colour. Tegmina have a conspicuous lateral pale stripe or margin, and the pronotum (head shield) has a sharply contrasting pale or yellow margin. It is very similar in appearance to the American cockroach and may be easily mistaken for it. It is however, slightly smaller than the American cockroach, has a yellow margin on the thorax and yellow streaks at its sides near the wing base.
Despite its name, the Australian cockroach is a cosmopolitan species, and an introduced species in Australia. P. australasiae probably originated in Africa. It is very common in the southern United States and in tropical climates, and can be found in many locations throughout the world due to its travels via shipping and commerce between locations. It can be found in Florida, California, and other coastal states.
The insect can travel quickly, often darting out of sight when someone enters a room, and can fit into small cracks and under doors despite its fairly large size. It is known to be very mobile; it also has wings which allow it to be quite a capable flier.