In Vernor Vinge's A Fire Upon the Deep there is a rather odd communication relay message that contained the keyword phrase "Hexapodia as the key insight":

Crypto: 0

As-Received-By: OOB shipboard ad hoc

Language-Path: Arbwyth->Trade 24->Cherguelen->Triskweline, SjK units

From: Twirlip of the Mists

Subject: Blighter Video thread

Keywords: Hexapodia as the key insight

Distribution: Threat of the Blight

Approved: yes

Date: 8.68 days since Fall of Relay

I haven't had a chance to see the famous video from Straumli Realm, except as an evocation. (My only gateway onto the Net is very expensive.) Is it true that humans have six legs? I wasn't sure from the evocation. If these humans have three pairs of legs, then I think there is an easy explanation for


The Language-Path field indicates that the message had been translated repeatedly, which implies that some of the odd wording may be the result of translation degradation.

However, the phrase "Hexapodia as the key insight" appears to have become rather well known. In fact, rather strange references to the quote appear around the internet.

Is there some significance of this phrase beyond the surface appearances? Why is this such a popular reference, when the actual reference in the book is dismissed as a casual instance of absurdity?

3 Answers 3


Spoilers in abundance:

It's a joke about Usenet as it was in the 1980s. Twirlip sounds eccentric and expresses himself poorly, but in fact his insight is dead on, and everyone should be listening to him/her/it.

Even the line about hexapodia as the key insight is correct and helpful -- the Skroderiders are unwitting tools of the Blight, and their skrodes have six wheels (which are pretty much the same thing as legs to something that lives in a gas giant's atmosphere).

Read this post for more analysis (which is also full of spoilers, of course).

The author commented about this in his notes (now available in the “special edition” of the book:

Note 601: Heh, heh: … or three pairs of wheels? I wonder what would have happened if Ravna had just read a little further. In some weird way, Twirlip knows the Secret of the Riders. I wonder how many people will catch this. It’s really not up to the level of a legitimate clue (I didn’t notice it until after I wrote it) — but if it were, Ravna would have instantly caught on to it. This is a special case of something you might use elsewhere: Even though the Known Net has enormous connectivity, the interests of the participants and the prejudices of the newsfilter software would tend to create virtual partitions. There could be large segments that, sometimes unknowingly, are ignoring each other. Most of the time this would just improve efficiency; in some cases great insights would be lost. (Hence, I bet some people or their automation would expend lots of effort dredging the unintelligible. Even that would not eliminate the problem.)

  • That's a take that hadn't occurred to me. None-the-less, Twirlip is deeply confused and out of touch---there is no way to construe humans as hexopedic. Commented Jan 30, 2012 at 19:27
  • 4
    Wow, I'd never noticed that Twirlip might be referring to the Skroderiders as hexapodic! I thought it was just a comical mistranslation.
    – user56
    Commented Jan 30, 2012 at 19:40
  • 16
    @dmckee: But that's the point: Twirlip is asking whether humans have six legs because they are widely assumed to be willing agents of the Blight (rather than victims), and Twirlip knows about some sort of connection between Hexapodia and the Blight - but humans are neither hexapodic nor agents of the Blight, while Skroderiders are both. Twirlip is correct, just not communicating effectively. Commented Jul 4, 2013 at 8:32

As far as I can tell this message---and the several more like it later in the book---is meant to draw attention to the lack of reliability of the Net of Million Lies. We're told that the author of these posts is at the far end of a narrow pipe and several stages of automatic translation using only middle beyond technology. He is clearly---even admittedly---speaking of things for which he lacks the basic foundational knowledge; much like many authors on the Usenet.

He/she/it has obviously formed a poor understanding of just what a "human" is, and may be a bit of a kook besides.


Mike Scott's reply above matches the overwhelming majority consensus on the issue, with which I also join.

However, an additional (as opposed to an alternative) interpretation exists that I've not seen mentioned elsewhere. Throughout those parts of the novel dealing with the interactions of the humans and the tines, there are several references to humans as "two-legs" and Tines as "four-legs". And especially in the Epilogs chapter, Vinge's main human and tinish characters -- even what's left of Flenser/Tyrathect -- are extremely optimistic and even joyous about the prospects of the two species' increasingly close collaboration, a kind of cultural/technological/intellectual symbiosis. In other words, a singular collaboration between "two-legs" and "four-legs".

I'll leave the arithmetic as an exercise for the reader...

  • 4
    When did Twirlip learn about the Tines? I'm not sure he ever did, which would mean his post had nothing to do with addition...
    – John C
    Commented Jan 30, 2013 at 11:10
  • 3
    Word of god confirms Mike Scott's answer and does not suggest the 4+2 collaboration (which seems strange to me since a pack doesn't have four legs).
    – user56
    Commented Dec 9, 2014 at 8:06
  • Hexapedia: Four legs good, six legs better! - Bonnie Dalzell, the author of 'Hexapedia', an essay in Galaxy, May 1976 Commented Dec 9, 2014 at 14:32

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