Durch Körperstreckung übt die Schwebfliege Druck auf das Vorderende des Tönnchens aus. Dieses platzt an präformierten Nähten. In meist weniger als einer Minute verläßt die Fliege das Tönnchen.

Three examples show the eclosion process. The fly exerts pressure on the preformed fracture lines of the puparium when it is ready to hatch. The dorsal and ventral puparium lids are pressed apart as the head appears. The antennae, which were held tightly against the head in the puparium, are freed to take up their regular positions. They fly pushes itself further out of the puparium with peristaltic movements of the body. Shortly after the mesothorax is visible, the front legs are drawn out, assisting and accelerating the eclosion process with pulling movements. After the mid and hind legs are free, the fly leaves the puparium sidways. The wings are then unfolded and the colouring process is completed.