The blood of the cockroaches does not have hemoglobin, which is what give human blood the red color. Hence, their blood lacks the red color, making it appear white.
To state the obvious, cockroaches are an insect, which means that their anatomy is different than the other creatures. Most people have noticed that cockroaches have white blood. This is because cockroaches lack hemoglobin in their blood. Hemoglobin is primarily made up of iron and is what gives human blood its red color. However, the blood of a female cockroach can appear to be slightly orange when she is carrying eggs. This is due to a protein vitellogenin that is present in the blood.
Hemoglobin is also responsible for carrying oxygen from the lungs to the body's tissues and returning carbon dioxide from the tissues back to the lungs. As cockroaches lack hemoglobin, their systems have to come up with an alternative. Cockroaches technically breathe and transfer oxygen through a system of tubes in their bodies, called tracheae. This system is similar to our circulatory system, except that instead of blood travelling through the tubes, it is air. Their blood is actually distributed throughout their body.
Cockroaches are interesting creatures to say the least. Nearly everyone has seen a cockroach; this is because they appear to be everywhere. There is rarely any place on this planet that is not inhabited by cockroaches. While everyone hates cockroaches, and considers them a pest, there are actually only 10 species of cockroaches that fall into the category of household pests. This is 10 out of 4,600 species of cockroaches.
Cockroaches are one of the oldest living species on this planet. The evolved into being about 350 million years ago, and continue to thrive today. This is despite of multitude of events, such as meteor strike, climate change, a couple of ice ages, and various other events that wiped out life for millions of other species. It is no wonder that people say cockroaches will inherit the earth after the humans have killed themselves off. They truly are capable of existing in a variety of climates.