Why Aren't Insect Tracheae Associated with Capillary Beds

Question

Why aren't insect tracheae associated with capillary beds?
A)Insect capillaries are found only around the gut.
B)Insects have an open circulatory system.
C)Insects have external gills associated with hemolymph vessels.
D)Insects use an air sac respiratory system.

Accepted Answer

Insects have an open circulatory system where hemolymph, rather than blood, circulates through their body cavity. Insects do not have capillary beds associated with their tracheae because the oxygen exchange happens directly at the tracheoles, which are thin and close to the insect cells.