American cockroach

The American cockroach, known scientifically as *Periplaneta americana*, is a large insect often found in human environments.

While many people consider them pests, they are fascinating biological subjects. They are sometimes called waterbugs, though they are not aquatic insects. They are also known by names like the ship cockroach or the Bombay canary. Despite their common name, these cockroaches are not native to the Americas. They originally came from Africa and the Middle East. They were introduced to the Americas starting in the 17th century through human commercial patterns, including the Atlantic slave trade. Today, they are found almost everywhere in the world due to global commerce.

The biology of the American cockroach is defined by its impressive size and life cycle. It is the largest of the common cockroach species. Its life cycle can last up to about 700 days. Before reaching adulthood, the insect undergoes metamorphosis through 6 to 14 molts, with 13 being the most common number.

The body is divided into three main sections: the head, the thorax, and the abdomen. The thorax, or trunk, is further divided into the prothorax, mesothorax, and metathorax. Each of these segments produces a pair of cursorial legs, which are legs specialized for running. The abdomen consists of 10 segments. These segments are protected by chitinous plates called sclerites, which include dorsal tergites, ventral sternites, and lateral pleurites.

The reproductive process of the American cockroach is quite complex. A female produces an egg case called an ootheca. This case is brown, purse-shaped, and about 8 mm long. The female carries the ootheca at the tip of her abdomen for about two days before placing it in a safe location. Inside the case, the eggs hatch into nymphs after 6 to 8 weeks. These nymphs are wingless versions of the adults. They must undergo 13 molts, or ecdysis, to reach maturity. This maturation process can take 6 to 12 months. Adult females can live for an additional year and produce an average of 150 young. The entire reproductive cycle can last up to 600 days.

Physical adaptations allow the American cockroach to survive in many environments. They possess large compound eyes. Each eye contains over 3,500 individual lenses called ommatidia. These hexagonal apertures provide mosaic vision. This type of vision offers high sensitivity, which is very useful for nocturnal vision at night. They are also incredibly fast runners. In one experiment, a cockroach reached a speed of 53 body lengths per second. This speed is comparable to a human running at 210 miles per hour. Their flattened, oval bodies allow them to squeeze into small cracks and under doors.

The genetic makeup of the American cockroach is also remarkable. It possesses the second-largest insect genome ever recorded. About 60% of its genome is made of repeat elements. The genome is highly specialized for sensing the environment. It contains 522 taste receptors, which is the largest number found in any sequenced insect. Specifically, 329 of these receptors are used for bitter taste perception. They also have 154 olfactory receptors for smelling. These genetic tools, along with enhanced immune and detoxification genes, help them adapt to living in human spaces.

American cockroaches are opportunistic omnivores, meaning they eat a wide variety of materials. They enjoy fermenting foods, cheese, sweets, and bakery products. They can even eat non-food items like leather, glue, hair, and the starch in book bindings.

They prefer warm, moist environments and thrive in temperatures around 30°C. They do not tolerate cold well. If temperatures drop to 10°C or below, many cockroaches will die within 72 hours. Because they can carry bacteria like *Salmonella* on their legs, they can pose a risk to food safety. They can also trigger allergies or asthma in some people through their feces and body parts.

Interestingly, these insects have been used in human systems for centuries. In traditional Chinese medicine, an ethanol extract of the American cockroach is used. This extract, called *Kāngfùxīn Yè*, is prescribed for tissue repair and wound healing. This connection shows how humans have interacted with this species for a long time. While they are often managed with glue board traps or insecticides, their ability to adapt remains a major part of their biology. Their presence in human history is a direct result of how humans have moved goods and people across the globe.