A pest of our own making: revealing the true origins of the not-so-German cockroach

🌈 Abstract

The article discusses the evolution and global spread of the German cockroach (Blattella germanica), one of the most common cockroach species found in buildings worldwide. It explores how this urban pest evolved and populated human dwellings, tracing its origins back to east India and Bangladesh.

🙋 Q&A

[01] Origins and Spread of the German Cockroach

1. What did the DNA sequencing study reveal about the origins of the German cockroach?

• The DNA sequencing study traced the origins of the German cockroach (Blattella germanica) to east India and Bangladesh, specifically finding that its DNA sequence was almost identical to that of Blattella asahinai from the Bay of Bengal region.
• The two species diverged from each other just 2,100 years ago, indicating a relatively recent evolution of the German cockroach.

2. How did the German cockroach spread from its native lands to the rest of the world?

• The first wave of migration emerged from the Bay of Bengal around 1,200 years ago, traveling westwards likely with the traders and armies of the expanding Islamic Umayyad and Abbasid Caliphates.
• The next wave moved eastwards around 390 years ago into Indonesia, probably traveling with European trading companies such as the British East India Company or the Dutch East India Company.
• The German cockroach arrived in Europe about 270 years ago, as evidenced by historical records from the Seven Years' War.
• The global expansion of the German cockroach occurred about 120 years ago, facilitated by global trade and improvements in transportation and housing conditions.

[02] Adaptation and Resistance

1. How did the German cockroach adapt to survive and thrive in human dwellings?

• The German cockroach evolved to become nocturnal and avoid open spaces, while retaining its wings.
• It developed a notorious ability to rapidly evolve resistance to many insecticides used in surface sprays, with resistance appearing within a few years.
• The cockroaches also evolved resistance to cockroach baits that relied on sugars to attract them, as those with a "sweet tooth" were killed while those with other taste preferences survived and reproduced.

2. What challenges does the evolution of the German cockroach pose for pest control efforts?

• The rapid evolution of insecticide resistance makes it difficult to find new active ingredients, given the high cost of discovery, safety tests, and registration.
• As the German cockroach continues to evolve and adapt to stay alive, the "arms race" between humans and the cockroach will go on for years to come, requiring the development of new strategies to counter their adaptations.
• Understanding how resistance emerges can help identify weak spots to exploit and develop better ways to counter the German cockroach's survival tactics.