I've literally never heard them called den mothers or spider mutants. The name "virginia" is literally in the game when you unlock their codex entry. Similar problems with armsy's page and the mutants page. It is possible someone fixed this before the names were in the game, and made sure the nicknames weren't the primaries. When the nicknames ended up being the official names inside of the in game codex they became the official names though. I've been an editor on enough wikis to know that when that happens anyone fixing things once and zooming has no chance of it sticking. Someone with an account give it a quick fix? - 96.235.40.158 17:26, 27 July 2016 (UTC)
Okay, so it actually is possible to kill spider - watch this video from 12:30 to 15:30.
Found spider above ground without going into any caves at all. Non-hostile till I threw mollys at it and got closer.
On 17 June 0.18, thrown 5 mollies at it and it's still not dead. Most likely made it stronger, bear in mind the above video is from july 2014.