I have to same milk jug set up and I started my potato grow with an ant infestation and it was pretty cool, an ant crawled into the hole of the tube coming out of the jug and it almost instantly died. but im sure it's not harmful to us.
try to soak them every time you water, plus spray the leaves with water, maybe leave a galloon jug with water, open, to help increase humidity.
As Joseph would say, "I doesn't know!"