Chainsaw insect

If Chainsaw insect attacks and the opponent activates cards like mirror force or dimensional prison does he gets to draw a card I am wondering this since it says he needs to battle the monster and not just declare an attack in order for the effect to work.

No need attacks or attacked a monster. D. Prison or Mirror Force no matter. But if your oppenent uses a card which negates attack you won't get draw. For example you don't get draw with Magic Cylinder. Because it negates attacking.

If your opponent uses Mirror Force or Dimensional Prison etc, he will not draw a card.

But why? Mirror Force or D. Prison don't negate atttacks of attacking monsters.

Chainsaw Insect's effect activates at the end of the Damage Step. If Chainsaw Insect gets removed from the field by Mirror Force etc, you never enter the Damage Step.