I read again the book and I found:
The next eighteen hours were nightmare. I shan’t tell much about it because I don’t remember much, just snatches, stop-motion scenes of horror. I have never liked spiders, poisonous or otherwise; a common house spider in my bed can give me the creeps. Tarantulas are simply unthinkable, and I can’t eat lobster, crab, or anything of that sort. When I got my first sight of a Bug, my mind jumped right out of my skull and started to yammer. It was seconds later that I realized that I had killed it and could stop shooting. I suppose it was a worker; I doubt if I was in any shape to tackle a warrior and win.
But that wasn’t all that went wrong. Just name it, it was fouled up. I didn’t know what was going on, of course; just stuck close behind Dutch, trying to shoot or flame anything that moved, dropping a grenade down a hole when ever I saw one. Presently I got so that I could kill a Bug without wasting ammo or juice, although I did not learn to distinguish between those that were harmless and those that were not. Only about one in fifty is a warrior but he makes up for the other forty-nine. Their personal weapons aren’t as heavy as ours but they are lethal just the same — they’ve got a beam that will penetrate armor and slice flesh like cutting a hard-boiled egg, and they co operate even better than we do... because the brain that is doing the heavy thinking for a "squad" isn’t where you can reach it; it’s down one of the holes.
Guess they have guns or rifles as the primary armament.