California Structural Pest Control – Branch 2 (Wood-Destroying Pests and Organisms) Practice Exam

Insects do not have blood in the same way that vertebrates do, as they possess a fluid called hemolymph. The color of hemolymph can vary significantly among different insect species. It is commonly green, yellow, or colorless due to the presence of pigments and the absence of hemoglobin, which is the molecule that typically makes blood red in vertebrates. Instead of relying on hemoglobin to transport oxygen, insects utilize a system of air tubes that deliver oxygen directly to their tissues, allowing for a different coloration in their circulatory fluid.

While some insects may have hemolymph that appears blue due to the presence of hemocyanin—an oxygen-carrying molecule that contains copper—it is less common and can vary in appearance. The variation in color primarily depends on the specific chemicals present in the hemolymph, making green, yellow, or colorless the most typical descriptions. This distinction is crucial for understanding insect biology and the differences in their physiology compared to other animals.