C1008 Long Hair Bat

From the stairs to the bottom, there are dead bats everywhere!

Although this thing liked dark and damp places, Bald Donkey Ermei's basement couldn't possibly have any gaps, allowing these little beasts to fly in. More importantly, how could such a tenacious thing die, or die in groups?

If it was said to use pesticides to poison and kill them, how much dosage would that require? Furthermore