Here's some more WIRRN continuity!
3999 AD (late July) The novel "Doctor Who Placebo Effect" takes place. The Wirrn are chased out of the Milky Way after they attack a human colony. They head for the Andromeda Galaxy.
~5,001 AD The Nerva Space Beacon is refitted into the Ark to protect against the Solar Flares. A group of Star Pioneers leave Earth and colonize Andromeda. The solar flares devastate the earth.
~6,000 AD After millions of deaths the descendents of the Star Pioneers finish destroying all of the Wirrn breeding grounds in Andromeda. One Wirrn Queen heads for earth.
~10,000 AD After traveling for thousands of years the Wirrn queen reaches earth and invades the Nerva Ark. Earth becomes habitable again but no one re-colonizes it.
~15,000 AD The majority of the events in "The Ark in Space" occur.
Other Notes (not already mentioned):
The Wirrn used to pupate in mindless herbivores until man destroyed their breeding grounds. They retain the knowledge (and to some degree the personality) of the beings they pupate in. The infectious slime actually carries the knowledge of the pupa. So if the egg is laid in Bob then the pupa will have all of Bob's knowledge - but ANYONE who is infected with Bob's slime will turn into a Wirrn and will have all of Bob's knowledge as well as their own knowledge!!! The Wirrn can reproduce without any host bodies if they have enough energy but they lose the benefit of a host's knowledge. The novel says they don't do this because it takes much longer.
Wirrn queens can grow to be 10 times larger then Wirrn drones. Wirrn queens communicate telepathically with their drones.
The Wirrn can live in the vacuum of space for thousands of years.
Fission Guns were used against the Wirrn - not Lasers. The novelization makes it clear that the Wirrn are immune to these weapons due to their exoskeleton armor. The 500,000-volt charge that hits the Wirrn queen kills her…slowly.
The Doctor Who novel "Placebo Effect" by Gary Russell has lots of new info on the Wirrn (the essentials of which are noted above).
Hope this helps!
Just remember, even though it’s a vacuum,
In space no one can hear you Clean.
-J.T.
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