Abstract: It was observed that during copulation air bubbles were introduced into the bursa copula trix from the male aedeagus in Sitotroga cereallela. This study was to find our in thisphenomenon the source of air, tile air pathway and the initiation and action of the air expelling. The resu. Lsa indicated that the air bubbles came from the tracheoles on the hinder portion of the ductus ejaculatorius, they travelled along the inter-space of the tubular structure to the aedeagus and were expelled through a pore located near the aedeagal extreme. It is inferred that air expelling is the result of enhaneed me'abolism of the ejaculatory duct in the formationof spermatophores.

Key words: Sitotroga cereallela——copulation——air expelling