Wife and I were chatting away about this earlier (perfectly normal discussion, right?) and the timeline as we understand it is something akin to
50's popcorn horror flicks > Starship Troopers > Alien (for the Giger aesthetic) > Tyranids > Zerg
Now Zerg are pretty definitely directly ripped from Tyranids, and I'm fairly certain Tyranids were born from the combination of Giger aesthetics with Starship Troopers-type bug hordes, and Troopers itself was massively influential to a lot of sci-fi, with its space marines and power suits and such (it was required reading for the marines in the cast of Aliens!).
But the rest is shaky and I don't know how much is missing. And there's many VERY VERY easy real world references (fire ants, etc.) creators may have also drawn inspiration from along the way. I guess Ender's Game might fit in there somewhere, but it always felt more tangential than a direct step on the line to modern "bug horde" sci-fi villains (especially since in that case the war is a misunderstanding and the bugs are far from "mindless").
I don't think Lovecraft was a big contributor this time, as the bug hordes as we know them in modern sci-fi are in most ways quite ordinary and not otherworldly at all (usually), and while Moorecock and Tolkien both wrote extensively about spiders and the bugs in Starship Troopers are occasionally referred to as 'arachnids', Tolkien's & Moorecock's creations tended to be solitary and anthropomorphized in many ways, rather than a hive-mind type horde like ants, bees, etc. as were depicted in Troopers
Anyone have any insights here? Especially for the exact source which might have inspired Starship Troopers' insect enemies? I've never seen any specific mention about that, but for all we know it could have been a simple anthill.