@splitshockvirus@RustyCrab Yeah I had that feeling as well when I watched the movie. In the book the bugs are basically like the Zerg, their technology is biological, they advance by selective breeding or controlled evolution or something. It was never a surprise to the humans in the books that the bugs weren't just bugs.
I think they actually had some peaceful relations with the bugs historically, and another human-like alien race, the skinnies, are actually allied with the bugs. They have a lot of different plausible ways they could have found out.
IIRC the conflict started because the humans and bugs tried to colonize the same planet. I have vague memories to that effect.