- Blooper: A Zarbi runs towards the camera and unexpectedly bumps into it.
- The Cast Showoff: A choreographer, Rosalyn de Winter, was consulted to develop the movements for the Zarbi, Menoptera and Optera, and the crew was so impressed with her that she was given the role of the lead Menoptera character in the story, Vrestin. (She was famously credited for "Insect Movement" in the closing titles.)
- Inspiration for the Work: Writer Bill Strutton was inspired by a childhood experience of being badly bitten when he interfered in a fight between two bull ants. His memories had been stirred by watching his own sons, aged six and four, fighting in a similar fashion.
- Troubled Production: The demanding nature of the serial took its toll on the production. The first episode required a 16-minute overrun, brought about by a variety of flubbed lines, missed cues, equipment problems, and troubles with the Zarbi costumes, one of which broke and had to be repaired. The start of recording on the third was delayed when it was found that some of the sets had not been delivered to the studio, and the Carsenome floor had not been painted. Lighting and camera problems continued to plague the increasingly frazzled cast, and this time taping went 37 minutes beyond the schedule. One of the Zarbi operators, his vision impaired by his costume, ran right into the camera. So rushed was the recording, however, that this blooper was retained in the finished episode.
- This may have actually been the straw that broke the camel's back for William Russell, who reportedly resolved to quit the show during the shooting of this serial.
- What Could Have Been:
- Originally, the Zarbi had the ability to spit venom, but Dennis Spooner instead created smaller, grub-like creatures to fulfil this function.
- The larvae guns were originally meant to be mini-Zarbi.
- Working Title: This story was originally entitled The Zarbi, and was made under the working title The Centre of Terror. Another working title is known to be The Webbed Planet.
Trivia / Doctor Who S2 E5 "The Web Planet"