What is a distinguishing feature of adult German cockroaches?

Adult German cockroaches are characterized by the presence of two dark, almost parallel stripes running down their backs, which is a key identifying feature of this species. These stripes are typically found on their pronotum, which is the area behind the head. This distinct coloration helps in differentiating them from other cockroach species, which may have different coloration or patterns.

In contrast, the option mentioning a single dark stripe does not accurately describe the adult German cockroach, as it specifically has two parallel stripes. The assertion that they are bright yellow is incorrect, as German cockroaches are generally a brownish color, and being the largest type of cockroach does not apply either, as they are relatively small compared to other cockroach species like the American cockroach. Hence, the presence of the two dark stripes is a crucial visual identifier for recognizing adult German cockroaches effectively.