The Mechanism of Respiration of Locusts and its Bearing on the Problem of Inhalation of Poison Dusts

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Abstract
1. Measurements of the spiracles and the tracheae of 5th instar hoppers and adults ofLocustaand adults ofSchistocercahave been made (see Tables I, II and IV). These measurements show that particles of dust which had passed a 300 B.S. Sieve (i.e., under 0·053 mm. in diameter) are small enough to enter all the spiracles and that the particles which had passed a 150 B.S. Sieve (i.e., under 0·104 mm. in diameter) could enter spiracles 1 to 4 and 10.2. It has been proved by the presence of particles of dust in the respective spiracles, that spiracles 1 to 4 are inspiratory in function and spiracles 5 to 9 expiratory under all conditions, while the function of spiracle 10 is expiratory when the locust is flying and inspiratory when it is motionless.3. The quantity of dust present in the tracheae increases with the length of exposure to the cloud of dust ; the quantity present after 10 seconds exposure is not regarded as sufficient to kill the locust.4. The action of external poisons is thought to be by direct penetration of the integument or through the nerve endings or both.5. The results given in this paper suggest that further work on the action of poison dusts should be concentrated on the investigation of direct penetration of the integument and of the nerve action, rather than poisoning through the respiratory system.