Mobs killed by potions of harming I or II dont drop loot or exp.

Image one:
Displays the spider trap and group of spiders to kill.
Image two:
Displays the effect showing the 2nd or 3rd harming potion killing the group of spiders all at once.
Image 3:
Displays the area directly below the spiders after killing them with potions of harming II. There are no drops or exp to be collected.
Image 4:
Displays the area directly below the spiders after letting them respawn and then killing them one by one via punching over a ten minute period. There are tons of drops and exp to collect.