So, I'll share my winning tactic for the Newton rescue mission.
Enter the area in front of the bunker, see the first beetle, move away from it, then throw a grenade at the end of the beetle opposite it, activate stealth mode, press Enter (to enter combat mode), and then press Spacebar while the beetles run to the same spot where the grenade exploded. They will remain there until you exit combat mode, but even after you exit combat, they will still wander nearby.
In the bunker, immediately enter stealth mode, close the doors leading to the storage room deep inside the bunker, then kill the lone beetle in the next room. Then, set about 15-17 traps near the doors, leaving yourself a path in front of the door. Open the door and, while stealth mode, set more traps. Once all the approaches are set with traps, wait for one of the bugs to step into one (or somehow provoke it into doing so). Once that happens, the fun begins! Grenades and Molotov cocktails are the best gifts for those damned cockroaches! And if you have a firearm, don't hesitate to give these little bastards one.
Good luck!