Figure 48.4 The Tracheal Gas Exchange System of Insects (A) In insects, respiratory gases diffuse through a system of air sacs and tubes (tracheae) that open to the external environment through holes called spiracles. (B) The spiracles of a hawkmoth larva run down its sides. (C) A scanning electron micrograph shows an insect trachea dividing into smaller tracheoles and still finer air capillaries.