Using light and electron microscopy, sperm packing has been studied in the large sperm bundles of an aeshnid dragonfly. Each large bundle is built up of variously-sized smaller bundles which probably reflects the intracyst formation procedure. It is proposed that initially there is a gathering of immature sperm cells into small bundles at several sites within the testicular cyst, and secondly all sperm heads are bundled together. This construction of subunits may be of importance to bundle break-down and release of individual sperm cells after transfer to the female reproductive organs.