I suspect that both Zerg and Protoss were originated from Alien and Predator Movies, though the Starship-Troopers is a extremely good approximation for Zerg.
It is said that starship troopers was the origin of the design, but considering the similiarities of not only Z but also the carbon copy of the marine and protoss kinda similar to Tau, I would think they just heavily homaged warhammer, specially if you look at Chris Metzen drawings, their style is similar to the old games workshop style.Maybe the idea of a bug race came from Starship troopers, but the design probably not.
Actually all 3 races of StarCraft were directly inspired by Warhammer. SC1 was originally intended to be a Warhammer game but 40k denied Blizzard so they changed the races just enough to be legally different.
That’s why the Terran marines have oversized armor suits like the Ultra-Marines
That’s why the Zerg are an insectoid looking race that adapts genetic abilities from other races, because the Tyranids were exactly that; though Tyranids lack a cognizant mouthpiece like the Overmind or Queen of Blades.
That’s why the protoss armor design looks like the Asuryani (a mix of tech and tribal); same with the over all racial design: expensive but powerful units, power fields, invisible assassin units, warping in structures instead of building them, a focus on psychic abilities, etc were all Asuryani things too
I will always consider Starcraft to be from Aliens (Zerg, Ripley Kerrigan) and Predator (Protoss) instead.
Tried to check dates on wikipedia, and as Warhammer seems to predate the Predator (ironic turn of words) movie by a bit, it could be a chain and both Aliens/Predator and Warhammer would be true ancestors, or I could just be wrong due to not knowing Warhammer thus not giving it the credit it deserves.
edit: back to the zergling specific case, while Zerg end up looking strangely like insects, I don’t think the base are necessarily that. Since the zergling was created based on a “dune runner”, maybe it’s based on a mix of desert animals, like fennecs, suricates, strides (tried to google “desert animals”). Interesting thing is that those animals often burrow (an ability later gifted to most zerg ground units regardless of their origin). But that’s based on a very quick search.
Ok didn’t know there was a book that came first. Was thinking of googling it first before posting for that reason. I just remember when the movie came out, it was late 90’s.