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#32: Circulatory System


Litinsects #32: Circulatory System

Sadly today’s picture has nothing to do with the post’s content but what I’m explaining today is kind of hard to photograph... the insect circulatory system

  • Ever wondered why insects don’t bleed red? Insect “blood” is actually called HEMOLYMPH. It does not contain iron-based hemoglobin or red blood cells like we rely on for oxygen transport so it’s usually yellow/green/gray in color

  • Their circulatory system plays no role in gas exchange. As I explained in a previous post, insects breathe via their tracheal system, which is a network of small tubes with openings along the side of the body

  • Insects have an OPEN CIRCULATORY SYSTEM, meaning their hemolymph is not contained within blood vessels. Instead, their tissues are bathed in hemolymph. One DORSAL VESSEL, a tube along the insect’s back, is responsible for the movement of hemolymph throughout the body through the contraction of muscles

  • Like with our own circulatory system, responsibilities include the movement of nutrients, hormones, and waste products throughout the body. The insect circulatory system is also responsible for destroying pathogens or parasites and helps stop “bleeding” through a clotting response at wound sites

  • Insects also use their hemolymph somewhat like a hydraulic system in various situations. Immediately after shedding their exoskeleton (aka molting) the body is still soft so individuals can pump hemolymph into certain areas to expand them before the exoskeleton hardens, giving them more room in their “new skeleton”. The movement of hemolymph is also used by insects to “pump” themselves out of a tight pupal case and then it is pumped in to their new wings to expand and flatten them before they harden, which usually takes a few hours
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