Doctor Who and the Zarbi

Affected by a strange force, the TARDIS is dragged down to the desolate planet of Vortis. Until they can discover what is holding them there, the Doctor and his friends are trapped on the planet... The Doctor, Ian and Vicki are captured by the Zarbi - huge ant-like creatures controlled by the parasitic alien Animus. Meanwhile, Barbara runs into a group of Menoptra, butterfly-like creatures that have been driven from their home planet by the Animus, and plan to return with an invasion force. But