Particular centuries are spelled out and lowercased.
the twenty-first century the eighth and ninth centuries the eighteen hundreds (the nineteenth century)
Dunno if that's right by Aussie rules, though. *g*
ETA: And of course, the above commenters have the right of it in that there needs to be a hyphen between first and century, as well, since the whole phrase modifies pheromones.
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Date: 2009-07-10 05:48 am (UTC)ETA: And of course, the above commenters have the right of it in that there needs to be a hyphen between first and century, as well, since the whole phrase modifies pheromones.