Some monsters are poisonous, and make you roll to save against some unpleasant effects. Most of the mundane monsters poison their target through injury... And that's where it gets strange See, for example, Monstrous Spiders. They are dealing STR damage to their victim through their bite - and yet, their Tiny and Small versions have (1d3-4) and (1d4-2) damage... Which seems odd to me
Does that mean that Small Monstrous Spiders only poison their victims if they roll 3-4 on their damage die, and tiny ones - only with 3 AND critical hits? Or do they poison their targets anyway despite inflicting 0 actual HP damage?