|The following is based on Fallout Tactics and some details might contradict canon.|
A giant mutant strain of ladybug with unstable body chemistry. Explodes when agitated, disturbed, angry or bored.”
Boom bugs are pretty much worthless compared to frag grenades, but there aren't a lot of grenades in the early stages of the game. Boom bug explosions can poison targets. They explode in a buggy, toxic mist that damages all targets within a 5 hex radius.
They can be found in large quantities (100+) on the dead bodies of the tribals at Peoria, where your mission entails retrieving 3 fusion batteries.
The hostile 'Beastlord' faction almost always carries a few Boom bugs with them in their war parties. This is on account of their use of animals and other nature-oriented weapons in combat.