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 German cockroach is very successful at establishing an ecological niche in buildings, and is hardy and resilient against attempts at pest control. Some sources of this resiliency are the lack of natural predators in a human habitat, the large number of nymphs produced from each ootheca case, the short period between birth and sexual maturity, and the roaches’ ability to easily hide. German cockroaches are thigmotactic, meaning they prefer close spaces, and small compared to other species, which makes them adept at fitting into small cracks and crevices, thereby evading humans and eradication efforts. Cracks and crevices near harborages are thus an effective placement for baits. However pest control methods must kill 95% of the overall population to be effective in a property due to the species’ fast reproductive cycle.
Other considerations for controlling German cockroach populations are the interactions between individuals. Females carry their oothecae containing 18-50 eggs (average of 32) on the ends of their abdomens during germination until just before hatching rather than depositing them like other species, a practice which would leave the eggs vulnerable to predation. After hatching, nymphs can survive by consuming excretions and moults from adults and thereby remain hidden from most insecticidal surface treatments.