Abstract: Locke recently proposed that insects have lungs, which raised a new concept and a new area of interest in insect physiology and morphology. The existence of lungs of 62 insect species, belonging to 37 families in eight common orders, was detected by means of anatomy and histology methods. The results showed that the pupae and adults of Leucania separata and Sylepta derogata have no distinct lungs. However, lungs exist in almost all larvae of Lepidoptera. The lungs become more distinct or clear in more advanced groups of Lepidoptera than in less advanced ones. Although the larvae or nymphs of the examined species of Orthoptera, Mantodea, Homoptera, Hemiptera, Coleoptera, Diptera, and Apidae (Hymenoptera) have no distinct lungs, their tracheae become more complex in more advanced groups than in less advanced ones. The tracheae of the larvae of Argidae (Hymenoptera) function as lungs. Our study concluded that lungs in the eight insect orders examined show a trend from nonexistence to existence and from simple to complex.

Key words: Insecta, respiration, respiratory system, lung, trachea, evolution