The Penetration of Derris through the Spiracles and Cuticle ofMelophagus ovinus, L.

Abstract

InMelophagus ovinus, derris dust is shown to be absorbed through the spiracles and tracheal system. The amount of dust entering the tracheae is governed by the structure of the inspiratory spiracles and the rate of flow of the inspired air.Factors stimulating the rate of respiration of the insect—i.e., increased muscular activity, the presence of 5 per cent. carbon dioxide and a rise in temperature, increase the rate of entry of derris into the body.Penetration of derris takes place slowly through the external cuticle at 30° C., but not at all at 20°C. It is postulated that the entry of derris through the cuticle probably depends on the hardness of the lipoid layer.