How Big Were Cockroaches in Ancient Times?

Cockroaches are one of the most ancient insects on earth, and they have been around for more than 300 million years. They are known for their ability to survive in harsh conditions, and their resilience has made them a subject of interest for scientists and researchers.

But have you ever wondered how big were cockroaches in ancient times? Let’s dive into the world of prehistoric cockroaches to find out!

Prehistoric Cockroaches

During the Carboniferous period, which occurred between 359 and 299 million years ago, cockroaches were much larger than they are today. The warm and humid climate during this period was perfect for their growth and development.

Some species of prehistoric cockroaches grew up to a foot in length, with a wingspan of up to 18 inches! These giant insects were among the largest creatures on earth during that time.

Modern Cockroach Sizes

Today, most species of cockroaches are much smaller than their prehistoric ancestors. The average size of a cockroach is between 0.5 inches to 2 inches in length.

However, there are still some species that grow larger than others. For example, the Australian giant burrowing cockroach can grow up to 3.5 inches in length, making it one of the largest modern-day cockroaches.

Why Did Cockroach Sizes Change?

So why did the size of cockroaches change over time? One theory is that the decrease in atmospheric oxygen levels over millions of years caused a reduction in insect sizes.

During the Carboniferous period, atmospheric oxygen levels were much higher than they are today. This allowed insects like cockroaches to grow larger because they could extract more oxygen from the air.

As atmospheric oxygen levels decreased over time, insects had to adapt by decreasing their body size to extract enough oxygen through their respiratory system.


In conclusion, prehistoric cockroaches were much larger than modern-day cockroaches, with some species growing up to a foot in length. The decrease in atmospheric oxygen levels over millions of years caused a reduction in insect sizes, which led to the smaller size of modern-day cockroaches.

Despite their smaller size, modern-day cockroaches are still a nuisance for many people and can cause health problems. It’s important to take preventive measures like keeping your house clean and free from food scraps to avoid attracting these unwanted guests.

Remember that even though they may not be as big as their prehistoric ancestors, they still have the ability to survive in harsh conditions and can be difficult to get rid of once they infest your home.