Worms reproduce sexually via the cross fertilization of segments, each of which contains a complete compliment of male and female reproductive organs (hermaphroditic).
Shelled embryos develop in the ovaries through spiral cleavage to become infective larvae with 3 pairs of hooks.
When ingested by beetles, these larvae use their hooks and secretory glands to penetrate the gut of the beetle and enter the haemocoel where they undergo complete metamorphosis into ‘cysticercoid’ larvae, replete with an adult scolex (ie. ‘head’), ready for establishment in the final (mouse) host.
Eggs are released with mouse faeces and thus dispersal is passive - through the movement and defecation of mice.