Abstract: The invention relates to a device for the preparation and insertion of at least one type of weft yarn into the shed of a weaving machine. The said device comprises a yarn metering-delivering member feeding a storage chamber used for temporarily storing a length of weft yarn before its insertion into the shed. The introduction of the weft yarn into the storage chamber and its extraction to be thrown by means of rotating rollers are effected via a single guiding channel which comprises a zone situated between the throwing rollers and close to the gripping line, said zone overlapping laterally with respect to the rollers and comprising a continuous longitudinal slot.