From a total of approximately 4500 roach species, the German type is one of the most frequently found, especially in places such as restaurants or other food related locations. However, these roaches are not only found in the food industry, but are also the most common species that roams around houses, apartments and hotels. Due to their small size, they can easily fit through cracks and crevices, and because of their fast mating abilities, they can rapidly multiply and reach a high population, leading thus to the infestation of the location. A pair of German cockroaches can produce up to 10.000 descendants in a year’s time.
Reproduction and distribution
The German cockroach (Blattella germanica) is a small species of cockroach, typically about 1.1 to 1.6 cm (0.43 to 0.63 in) long. In colour it varies from tan to almost black, and it has two dark, roughly parallel, streaks running from behind the head to the base of the wings. Although Blattella germanica has wings, it can barely fly, although it may glide when disturbed. Of the few species of cockroach that are domestic pests, it probably is the most widely troublesome example.
The German cockroach reproduces faster than any other residential cockroach, growing from egg to reproductive adult in approximately 50 – 60 days. Once fertilised, a female German cockroach develops an ootheca in her abdomen. The abdomen swells as her eggs develop, until the translucent tip of the ootheca begins to protrude from the end of her abdomen, and by that time the eggs inside are fully sized. A small percentage of the nymphs may hatch while the ootheca is still attached to the female, but the majority emerge some 24 hours after it has detached from the female’s body. The newly hatched 3mm-long black nymphs then progress through six or seven stages before becoming sexually mature, but this process of molting is such a hazardous process that nearly half the nymphs die of natural causes before reaching adulthood. Molted skins and dead nymphs are soon eaten by living nymphs present at the time of molting.
Behaviour as pests
Blattella germanica occurs widely in human buildings, but is particularly associated with restaurants, food processing facilities, hotels, and institutional establishments such as nursing homes. In cold climates, they occur only near human dwellings, because they cannot survive severe cold.
Regarding points of access, these cockroaches can gain entry inside households through gaps, open doors, beneath the thresholds of doors, pipes, utility lines, drains, sewers, toilets, bathtubs, sinks, radiators, etc. Once inside, because they are so sluggish, they tend to remain on the bottom floors or those below ground, preferring basements, cellars, or other damp locations, usually around decaying organic matter and large sources of water. In the case of apartment complexes, they might reach the upper floors through garbage chutes.
As they prefer warm spaces and they can eat almost anything, including sweets, flour and fat, they can invade your kitchen and appliances such as the microwave, refrigerator and oven, and can also spread to the rest of the house.
They prefer confined spaces, and they are small compared to other pest species, so they can hide within small cracks and crevices that are easy to overlook, therefor evading humans and their eradication efforts. Conversely, the seasoned pest controller is alert for cracks and crevices where it is likely to be profitable to place baits or spray surfaces.
The German cockroach is resilient in the face of many pest control measures due to its lack of predators in the human habitat, its voluminous reproduction and its ability to adapt and even develop an immunity against chemical pesticides. Having a short reproductive cycle and reaching sexual maturity within weeks also helps the German cockroach in developing a large invading population.
To be effective, control measures must be comprehensive, sustained, and systematic; survival of just a few eggs is quite enough to regenerate a nearly exterminated pest population within a few generations, and recolonisation from surrounding populations often is very rapid, too.