Spiders that have formed armies 50,000 strong

That is interesting - one of the postulated prerequisites for sociality in insects is haplo-diploidy, where one gender is haploid and the other is diploid, like it happens in bees and ants.

This leads to the curious outcome where sisters are closer related to their sisters than to their daughters: https://en.wikipedia.org/wiki/Haplodiploidy#Relatedness_rati...

I assume these spiders are all diploid?

Wikipedia says that part of the social behaviors in these spiders is that they don't discriminate towards foreign offspring. I'm reminded of Argentine super-colonies, which are ant species which form enormous colonies stretching several hundred kilometers but which may or may not be genetically distinct - one hypothesis as to why they cooperate and not fight is this:

>the reason ants in the Mediterranean don't fight is that, although they are genetically diverse, they have lost the diversity in the genes that are involved in recognition and thus don't recognize each other as different.

Source, 2004: http://news.stanford.edu/news/2004/april7/antstudies-47.html

Wonder whether these spiders have the same thing!

Along similar lines. Anyone with a shark phobia has something new to fear: Great whites also hunt in packs.

>At Seal Island, white sharks arrive and depart year after year in stable “clans” of two to six individuals. Whether clan members are related is unknown, but they get along peacefully enough. In fact, the social structure of a clan is probably most aptly compared to that of a wolf pack.

http://www.naturalhistorymag.com/picks-from-the-past/191391/...

John Wyndham's SF novel 'Web' (https://en.wikipedia.org/wiki/Web_(novel)) was an interesting exploration of spider cooperation - uncannily close to the observations detailed in this article, but written in the 1960s!

If anyone would like to revel in the goosebumps this awesome article elicits, I found a sweet list of spiders in film up to 2007:

http://public.wsu.edu/~delahoyd/spider.films.html

Natures own social network.

You don't get to 50,000 friends without eating a few enemies.