Answer:
12.5 tons
Step-by-Step Explanation
There are 2 million bats and they eat 10 tons so 1 million bats would eat 5 tons half of 5 is 2.5 so if there where 2.5 million bats then you would increase the number of insects by half of a half or 2.5 because the number increased by half a million and 1 million bats eat 5 tons. Hope this was helpful :D