Visible crew/equipment: When they capture the brain bug, just before Carl says "It was a man called Zim [who captured the bug]", you can see a microphone antenna shadow is visible on his back. The shadow of the camera on his shoulder can also be seen in the fullscreen DVD edition. (01:57:35)
Visible crew/equipment: In the scene towards the end, in the cavern containing the brain bug, there's a pyrotechnic set-piece of a massive quantity of ammo being used up. This was filmed from a number of angles, and in one shot, looking down across the cavern there is a camera man and an assistant visible in the mouth of one of the tunnels leading in. I don't know if this is corrected in the DVD release, but it was certainly there in the UK theatrical version.
Visible crew/equipment: When Rico gets thrown from the tanker bug and lands on his back on the ground, a piece of the flap covering the mattress pops up.
Visible crew/equipment: When Rasczak tells everybody to fall back into the compound and "hold what they've got", there is a shot of one of the bugs being killed and landing on some silver containers, knocking them over. The wires used to pull the containers over are visible. (01:32:35)
Chosen answer: They do use nukes (to clear out bug caves) and fuel-air bombs (like they do before landing troops). It's possible biological and chemical weapons don't work on the bugs because of their physiology. Only nukes and Thermobaric weapons work.
lionhead